July 25, 2013
The Honorable David L. Strickland
Administrator
National Highway Traffic Safety Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Request for Comments; Planned Update to U.S. New Car Assessment Program; 49 CFR Part 575,
New Car Assessment Program (NCAP); Docket No. NHTSA-2013-0076
Dear Administrator Strickland:
The National Highway Traffic Safety Administration (NHTSA) has requested comments on a proposed
update to the U.S. New Car Assessment Program (NCAP) to provide information concerning rearview
video systems on vehicle models listed on the agency’s website, safercar.gov. NHTSA plans on using a
two-phase approach. Initially, rearview video systems will be listed in the “Safety Features” section of the
website for vehicle models with the feature. In the second phase, vehicle models with rearview video
systems that meet the performance requirements described in the agency’s proposed amendment to
Federal Motor Vehicle Safety Standard No. 111 (Office of the Federal Register, 2010) will receive credit in
the “Recommended Advanced Technology Features” section of the website. The Insurance Institute for
Highway Safety (IIHS) has supported NHTSA’s efforts to promote countermeasures to increase driver
awareness of objects to the rear of the vehicle (IIHS, 2009, 2011), and we agree that promoting rearview
video systems through NCAP is a useful step toward addressing the backover crash problem.
Backing crashes represent only a small proportion of all highway crashes, but can be tragic because
injuries or fatalities in backover crashes typically involve young children and families. The potential of
rearview video systems to address the backover crash problem is well established. Rearview video
systems greatly increase visibility behind the vehicle. IIHS recently measured rear visibility in 21 2010-13
vehicles and the improvements in visibility provided by rearview video systems and areas behind the
vehicle detected by rear parking sensors (Kidd and Brethwaite, 2013). Rearview video systems
decreased blind zones, defined as the areas not visible in side mirrors, rearview mirrors, or using direct
glances over the right shoulder of a 50th percentile male, by 72-99 percent across the vehicle sample.
Experimental studies have found rearview video systems help drivers avoid an unexpected stationary and
moving obstacle in the backing path when the system is used while backing (Kim et al. 2012; Mazzae,
2010; Mazzae and Barickman, 2008). Additionally, rearview video systems are the most capable
technological solution available, as other technologies like ultrasonic sensors have not be shown to be
reliable or as effective at enhancing awareness of objects behind the vehicle (Mazzae and Garrott, 2006).
Past research suggests rearview video systems should have a measurable effect on backing crashes,
but, to date, there is little evidence to suggest these systems are preventing crashes and reducing loss.
In 2011, the Highway Loss Data Institute (HLDI) compared insurance claim frequencies for physical
damage to the at-fault vehicle (collision coverage) and physical damage to a struck vehicle or other
property (property damage liability coverage) in select Mazda and Mercedes-Benz vehicle models with a
rearview video system with the same vehicle models without the system (HLDI, 2011, 2012). As shown in
Table 1, changes in claim frequencies were directionally inconsistent across coverage types and
statistically significant reductions in claim frequencies were not observed. In a naturalistic driving study of
backing maneuvers conducted by NHTSA, 6 backing crashes were observed in a sample of 37 drivers of
2007 Honda Odyssey minivans during 4 weeks of driving (Mazzae and Barickman, 2008). Of the 6
crashes, 5 involved drivers whose vehicle had a backup camera system. Four of these 5 drivers’ vehicles
also had a parking sensor system.
David L. Strickland
July 25, 2013
Page 2
Table 1
Percent change in insurance claim frequency per insured vehicle year
for select Mazda and Mercedes-Benz vehicles with rearview video systems
compared with those without the systems by coverage type
Make
Collision
a
c
Mazda
+3.1
b
Mercedes-Benz
+0.5
a
HLDI (2011), b HLDI (2012), c p<0.05
Coverage type
Property damage liability
-2.3
-0.5
These preliminary findings suggest the real-world effectiveness of rearview video systems may not be as
beneficial as expected, but more extensive evaluations are required. NHTSA’s proposed update to the
NCAP program may accelerate the penetration of rearview video systems in the U.S. passenger vehicle
fleet. Having more passenger vehicles equipped with rearview video systems on the roadways will allow
HLDI, NHTSA, and others to better estimate the real-world effectiveness of rearview video systems.
Rearview video systems currently might be the best means of increasing drivers’ views of the areas
behind their vehicles, but many drivers still rely on mirrors or rearward glances to maintain awareness of
their surroundings while backing (Mazzae and Barickman, 2008). In our evaluations of rear visibility, we
were surprised to see several instances where smaller passenger cars had larger blind zones than larger
trucks or minivans (Kidd and Brethwaite, 2013). As IIHS has expressed in previous comments, we
encourage NHTSA to consider implementing direct rear visibility requirements for all vehicles (IIHS,
(2009, 2011). Having an available rearview video system on a vehicle model should not justify design
choices that restrict direct visibility around the vehicle.
In summary, the tragic nature of backover crashes justifies NHTSA’s continuing efforts to promote
rearview video systems. IIHS supports the inclusion of rearview video systems in NCAP and will continue
to monitor the effects of these systems in the real world. Rearview video systems might only be a partial
solution to the backover crash problem, so we encourage NHTSA to consider additional measures to
address this issue such as regulating the size and position of directly viewable areas behind vehicles.
Sincerely,
David G. Kidd, Ph.D.
Research Scientist
Attachment
Kidd, D.G. and Brethwaite, A. 2013. Visibility of children behind 2010-13 model year passenger vehicles
using glances, mirrors, and backup cameras and parking sensors. Arlington, VA. Insurance Institute for
Highway Safety.
References
Highway Loss Data Institute. 2011. Mazda collision avoidance features: initial results. Bulletin 28(13).
Arlington, VA.
David L. Strickland
July 25, 2013
Page 2
Highway Loss Data Institute. 2012. Mercedes-Benz collision avoidance features: initial results. Bulletin
29(7). Arlington, VA.
Insurance Institute for Highway Safety. 2009. Comment to the National Highway Traffic Safety
Administration concerning proposed amendments to rearview mirrors standard and no-blind-spot
requirement to reduce deaths and injuries associated with backover crashes (Docket no. NHTSA-20090041). Arlington, VA.
Insurance Institute for Highway Safety. 2011. Comment to the National Highway Traffic Safety
Administration concerning modification of Federal Motor Vehicle Safety Standard 111 Rearview Mirrors to
require systems to enhance visibility of the areas directly behind the vehicle (Docket no. NHTSA-20100162). Arlington, VA.
Kidd, D.G. and Brethwaite, A. 2013. Visibility of children behind 2010-13 model year passenger vehicles
using glances, mirrors, and backup cameras and parking sensors. Arlington, VA. Insurance Institute for
Highway Safety.
Kim, R.; Rauschenberger, R.; Heckman, G.; Young, D.; and Lange, R. 2012. Efficacy and usage patterns
for three types of rearview camera displays during backing up. SAE 2012 World Congress & Exhibition
(Paper no. 2012-01-0287). Warrendale, PA: Society of Automotive Engineers.
Mazzae, E.N. 2010. Drivers’ use of rearview video and sensor-based backing aid systems in a nonlaboratory setting. Docket no. NHTSA-2010-0162. Washington, DC. National Highway Traffic Safety
Administration.
Mazzae, E.N. and Barickman, F. 2008. On-road study of drivers’ use of rearview video systems
(ORSDURVS). Report no. DOT HS-811-024. Washington, DC. National Highway Traffic Safety
Administration.
Mazzae, E.N. and Garrott, W.R. 2006. Experimental evaluation of the performance of available backover
prevention technologies. Report no. DOT HS-810-634. Washington, DC. National Highway Traffic Safety
Administration.
Office of the Federal Register. 2010. Federal Register, vol. 75, no. 234, pp. 76186-76250. National
Highway Traffic Safety Administration, Docket no. NHTSA-2010-0162, 49 CFR Parts 571 and 585:
Federal Motor Vehicle Safety Standard, Rearview Mirrors; Federal Motor Vehicle Safety Standard, LowSpeed Vehicles Phase-in Reporting Requirements. Washington, DC: National Archives and Records
Administration.
Visibility of Children Behind 2010-13 Model Year
Passenger Vehicles Using Glances, Mirrors, and
Backup Cameras and Parking Sensors
July 2013
David G. Kidd
Insurance Institute for Highway Safety
Andrew Brethwaite
Insurance Institute for Highway Safety
1005 N. Glebe Rd., Arlington, VA 22201 Tel. 703/247-1500 Fax 703/247-1588 www.iihs.org
ABSTRACT
It is estimated that about 18,000 people are injured and 292 are killed annually in backover
crashes. A little more than 10 percent of these injuries involve children younger than 5, but older children
also are frequently injured in backing crashes. Visibility of the areas behind the vehicle influences how
well drivers can detect and avoid obstacles while reversing. Previous research has measured rear
visibility in an assortment of vehicles for a 1-2-year-old child as a worst case scenario. The current study
measured rear visibility for 12-15 month-olds, but also examined visibility for 30-36- and 60-72-month-old
children. The purpose was to identify the areas behind vehicles where younger and older children are not
visible and determine the extent to which vehicle technologies like backup cameras improve visibility and
parking sensors detect objects in areas that are not visible.
Rear visibility in 21 2010-13 model year vehicles with a backup camera system or a backup
camera and rear parking sensor system was assessed in an area that was 20 feet wide and extended 70
feet from the rear bumper. A 50th percentile male observer was used to make judgments about the
visibility of targets simulating the height of a child 12-15 months old (30.2 inches tall), 30-36 months old
(36.8 inches tall), and 60-72 months old (42.7 inches tall). Judgments were made using the left and right
side mirrors, rearview mirror, glances over the right shoulder through the rear window, backup camera,
and parking sensors (if available). The area behind the vehicle where each target was not visible (blind
zone) and the average sight distance from the rear bumper to the target were used to characterize rear
visibility for each vehicle. The size of the image in the backup camera display from the midpoint of the
observer’s eyes also was assessed.
2
The average blind zone for a 12-15-month-old child (240.24 ft ) was twice as large as the
2
average blind zone for a 60-72-month-old child (116.67 ft ). Average sight distance from the rear bumper
to a 12-15-month-old child-size object (27.3 feet) also was twice as far as it was for a 60-72-month-old
child-size object (13.2 feet). On average, large SUVs had the worst rear visibility, i.e., largest blind zone
and longest rear sight distance, and small cars had the best visibility. Generally, the size of the vehicle
was positively associated with the size of the blind zone and average sight distance from the bumper.
However, there were exceptions to this pattern. Some cars, like the Infiniti M37 and Hyundai Sonata, had
worse rear visibility for a 12-15-month-old child than larger pickup trucks and minivans.
On average, backup cameras and backup cameras combined with parking sensors reduced the
blind zone for the different target heights by around 90 percent. Furthermore, these systems drastically
reduced average rear sight distance from the bumper to the different child-size objects to less than 2 feet.
On average, increases in rear visibility provided by backup cameras were larger than the non-visible
areas detected by parking sensors, but parking sensors detected objects in areas near the rear of the
vehicle that were not visible using direct glances, mirrors, and backup cameras. Finally, the image size of
each vehicle’s backup camera display met the federal government’s proposed requirements.
This study was the first to assess rear visibility for taller child-size objects among vehicles in
various classes. Although rear visibility typically was better for 60-72-month-old child-size objects than for
1
12-15-month-old child-size objects, a 42.7-inch tall object was not visible up to 13 feet behind the vehicle.
Backup cameras and parking sensors nearly eliminated the blind zone behind each vehicle. Based on
their functionality, vision enhancing technologies can mitigate or completely prevent backing crashes.
However, behavioral studies have found that drivers still may collide with child-size objects when
reversing even when using backup cameras and parking sensors. Additional research is needed to better
understand how drivers use the technologies, to identify which technology features optimize their use,
and to devise ways to get drivers to use them optimally. Crash avoidance technology that automatically
brakes when a backup collision is eminent also is a promising alternative solution.
INTRODUCTION
Backover crashes can result in severe and fatal injuries to pedestrians or people standing behind
the vehicle. Based on data from the Not-in-Traffic Surveillance (NiTS) system, the Fatality Analysis
Reporting System, and the National Automotive Sampling System General Estimates System, an
estimated 18,000 injuries and 292 fatalities occur each year due to backover crashes (Austin, 2008).
About 2,000 of these injuries were estimated to involve children younger than 5. Children are at a higher
risk of being involved in a backover crash because their shorter stature makes them harder to see.
One factor that contributes to backover crashes, especially those involving children, is vehicle
rear visibility. Rear visibility typically is worse in larger vehicles like trucks and SUVs compared with
passenger cars. Consumer Reports (2012) measured the distance from the vehicle’s rear bumper to the
location where a cone 28 inches tall was first observed by drivers 5 feet, 1 inch and 5 feet, 8 inches tall
using glances over the right shoulder. The 28-inch cone was used to approximate the height of a 1-yearold child. For the 5-foot, 1-inch driver, the average rear sight distance was longest for pickups and
shortest for minivans. Pickups also had the longest rear sight distance for the 5-foot, 8-inch driver, and
midsized sedans had the shortest.
The National Highway Traffic Safety Administration (NHTSA) assessed rear visibility in passenger
vehicles using a human driver (Mazzae & Garrott 2008) and a laser-based measurement system (;
Mazzae, 2013; Mazzae & Barickman 2009). The primary measure in these studies was blind zone,
defined as the area behind the vehicle that was not directly visible using glances over the shoulder or
through side windows, indirectly visible using side mirrors and the rearview mirror, or some combination
of these fields of view. The blind zone for a 1-year-old child-size object typically was larger for large
pickup trucks, cargo vans, and SUVs than it was for passenger cars.
Given that rear visibility is poorer in larger vehicles than smaller vehicles, it is not surprising that
larger vehicles are more frequently involved in backover crashes involving children. Pinkney et al. (2006)
examined police crash reports in Utah from 1998 to 2003 involving children younger than 10 struck by a
motor vehicle on a residential driveway. The children were 53 percent more likely to be injured by a
pickup truck than a passenger car, relative to registrations of each vehicle type, and 141 percent more
2
likely to be injured by a minivan than a passenger car. They also were more likely to be injured by an
SUV than a passenger car, but this difference was not statistically significant.
Mazzae and Garrott (2011) performed a Monte Carlo simulation using data from a naturalistic
study of backing maneuvers to estimate the probability of a reversing vehicle striking a pedestrian moving
at a constant speed and direction behind the vehicle. The probability of a backover crash was highest
when the pedestrian’s starting position was immediately behind the rear bumper and decreased as the
starting location moved away from the rear bumper. However, a crash occurred in 40 percent or more of
the simulated trials where the pedestrian’s starting position was located 15 feet or less directly behind the
rear bumper. This area is typically not visible to a 50th percentile male driver using mirrors or glances
over the shoulder in most vehicles.
Backing technologies such as ultrasonic parking sensors and backup cameras can enhance
visibility or detect objects behind the rear of the vehicle and help prevent backover crashes. Ultrasonic
parking sensors detect objects behind the vehicle by emitting ultrasonic sound waves from the rear of the
vehicle. If an object is present, the wave reflects off the object and returns to the vehicle where it is
detected by a sensor. Distance and location information is relayed to the driver with a visual display or
auditory tone. A disadvantage of parking sensor systems is that they have limited detection range. One
study reported that owners typically turned sensor systems off because they were not reliable (Mazzae &
Garrot 2006). Drivers who reverse too fast also may exceed the functional capabilities of sensor systems,
rendering them useless (Llaneras et al., 2005). Finally, one study found that sensor systems had
difficulty detecting pedestrians, especially moving children (Mazzae & Garrott, 2006).
Backup cameras display the area directly behind the vehicle on a screen generally located in the
vehicle center console or rearview mirror. Backup cameras are passive and do not alert drivers about
objects behind the vehicle. Thus, the driver must look at the display to detect and respond to obstacles.
Some newer vehicles combine sensor-based systems and backup cameras.
Several organizations are working to encourage auto manufacturers to fit vehicles with backing
technology. The Insurance Australia Group (IAG, 2013) rates vehicle rear visibility using a reversing
visibility index. Ratings are based on the area where a laser positioned at the approximate eye location
of a driver 70.1 inches tall and directed through the rear window is observed on a cylinder 23.6 inches tall
in an area 5.9 feet wide and 49.2 feet long behind the vehicle (Paine et al., 2003). Vehicles are awarded
up to 5 stars based on the area of the test grid where the child-sized cylinder is visible, and an extra 0.5
star is awarded to vehicles with backing technology.
In the United States, NHTSA has proposed rulemaking to require manufacturers to provide
drivers a way to see seven cylinders 32 inches tall placed along the perimeter of an area 10 feet wide and
20 feet long directly behind the vehicle when the vehicle is placed in reverse (Office of the Federal
Register, 2010). NHTSA’s proposed rule does not require a specific technology, or any technology at all,
but backup cameras are currently the only technology that will meet the proposed minimum visibility
requirements.
3
To date, assessments of rear visibility have been limited to shorter objects reflecting the height of
a 1- or 2-year-old child. Young children represent the “worst case scenario” for rear visibility, but older
children also are involved in backover crashes. A study using the Canadian Hospitals Injury Reporting
and Prevention Program database found that, between 1993 and 2004, about 12 percent of pedestrianmotor vehicle collisions involving children younger than 5 were backovers (Nhan et al., 2009). About 4
percent of pedestrian-motor vehicle collisions involving 5-13 year-olds were backovers.
The improvement in rear visibility provided by different technologies in different vehicles has not
been systematically evaluated. The purpose of the current study was to characterize rear visibility for 1215-, 30-36-, and 60-72-month-old children in 2010-13 model year passenger vehicles, and measure the
additional visibility provided by backup cameras for each age group and areas where each age group was
not visible but detected by parking sensors. The image size of vehicles’ backup camera displays also
was examined to determine whether current camera systems meet the functional requirements proposed
by NHTSA.
METHOD
Vehicle Sample
Twenty-one 2010-13 model year passenger vehicles with a backing camera system or a backing
camera and rear parking sensor system were evaluated (Table 1). Candidate vehicles were limited to the
manufacturers and models available at dealerships in the Charlottesville, Virginia, area. Efforts were
made to include 2012 models with the largest sales volumes. At least two vehicles in each vehicle class
were included.
Target and Measurement Field
The visual target was a cylinder 42.7 inches tall and 4.5 inches wide (Figure 1). Three different
color bands were painted onto the cylinder. The distance from the bottom of the cylinder to the top of
each color band corresponded with the 50th percentile standing heights of a 12-15-, 30-36-, and 60-72month-old child (Tilley, 2002). The standing heights simulated by the visual target were 30.2, 36.8, and
42.7 inches for each age group, respectively. The height of each color band corresponded with the
average head width of a 50th percentile child in each age group (Tilley, 2002). The heights of the color
bands simulating the head heights of a 12-15-, 30-36-, and 60-72-month-old child were 5, 5.3, and 5.4
inches, respectively.
Visibility from various direct and indirect fields of view was measured using a measurement field
20 feet wide that extended longitudinally 5 feet in front of the rear bumper and 70 feet behind the rear
bumper of each vehicle (Figure 2). The measurement field was divided into 1- by 1-foot squares using 1inch wide tape adhered to a flat concrete surface. Six different fields of view were measured and
included the (a) left side mirror, (b) right side mirror, (c) rearview mirror, (d) glances over the right
shoulder, (e) areas visible in the backup camera display, and (f) areas detected by the rear parking
4
sensor system. Visibility for the three target heights using each field of view was assessed at each
square in the measurement grid. Only visibility judgments made at or behind the rear bumper (0-70 feet
in Figure 2) are reported in the current study.
Observers and Inter-Observer reliability
Visibility judgments were made by two male observers who were similar in stature and seated
eye height to each other and a 50th percentile male (Table 2; Gordon et al., 1989). The observers were
Insurance Institute for Highway Safety (IIHS) employees and were assigned to different vehicles based
on the employee’s availability. The observers were selected from four candidate observers based on
inter-observer agreement data collected in a pilot study.
In the pilot study, observers made visibility judgments for the three visual target heights in up to
three different vehicles. The percent of agreement between observations made by pairs of observers’ for
each target height using each field of view were analyzed. Cohen’s Kappa also was calculated as a
second measure of inter-observer agreement (Cohen, 1960). Observers TV and DK showed a high
percent of agreement between their visibility judgments for different target heights across nearly every
field of view in three different vehicles. Their percent agreement was above 90 percent for judgments
made using side and rearview mirrors, but was lower for judgments made using glances over the right
shoulder (60-90 percent). Cohen’s Kappa of the visibility judgments made for different target heights with
mirrors showed substantial (0.61-0.8) or almost perfect (>0.8) agreement. Visibility judgments made
using glances over the right shoulder also showed substantial or almost perfect agreement for all three
target heights in two of the three pilot study vehicles and the shortest target height in the third vehicle.
Visibility judgments for the 36.8- and 42.7-inch target heights in the third vehicle showed low agreement
(0.01-0.2). Overall, the results indicated a high degree of correspondence between the visibility
judgments made by observers TV and DK, and the agreement between these observers was higher than
for the other pairs of observers. Thus, observers TV and DK were used in the full study.
Vehicle Preparation
The following procedure was used to prepare each vehicle to enhance repeatability of visibility
judgments. First, the vehicle tires were inflated to the manufacturer’s recommended inflation pressure
and the vehicle’s dimensions were measured. The vehicle’s fuel tank was either filled to capacity or
weight was added to approximate the weight of the fuel needed to fill the tank to capacity; 6.1 pounds of
weight were added per gallon of fuel (Marathon, 2010). The vehicle’s rear passenger windows were
cleaned and closed. The driver and front passenger windows were slightly open to allow for better
communication between the observer and the researcher recording measurement data. If a window
sticker obscured the view of the observer, then the sticker was removed or the window with the sticker
was rolled down. The driver and front passenger seats were positioned for a 50th percentile male using
the University of Michigan Transportation Research Institute (UMTRI) anthropometric test device (ATD)
5
positioning procedure (IIHS, 2004), which is used by IIHS to position ATDs in frontal crash tests. The
vertical position of the driver seat head restraint was even with the topmost point of the observer’s head
or set at the highest vertical height of the head restraint, whichever was lower. All other head restraints
were in upright positions, set to the lowest vertical height. If fore-aft adjustment of the head restraint was
possible, then the driver head restraint was set to the forward-most position and the right front passenger
and rear passenger head restraints were set to the midpoint position. If the second and third row seats
were adjustable, the seat pan was set to mid-track position and the seat back angle was set to 25
degrees. Every front and rear passenger seat belt was buckled, including those originating from the
headliner for center seating positions.
Once the vehicle was prepared it was positioned on the measurement field. The vehicle’s rear
bumper was positioned flush with the 20-foot lateral axis of the measurement field at the origin of the
longitudinal axis (i.e., 0-foot line). The vehicle’s centerline was positioned in the center of the lateral axis
allowing for lateral measurements ranging between 10 feet to the right and left of the vehicle centerline.
Next, the observer entered the vehicle, sat in the driver’s seat, and buckled the seat belt. Then
the observer positioned the side and rearview mirrors. The position about the vertical axis for the left and
right side mirrors was set so that the side of the vehicle was slightly visible at the most inward point of the
mirror. This setting was found to be the most common position for side mirrors among a representative
sample of drivers (Reed et al., 2001; Reed et al., 2000). The position about the lateral axis for the side
mirrors was set so the horizon was vertically centered in the mirror. Lastly, the observer adjusted the
rearview mirror to be able to see through the entire rear window.
Measurement Procedure
The visual target was placed on individual squares in the measurement field. The observer was
instructed to indicate the shortest target height that was visible using different fields of view. To be
visible, the full width and height of the color band corresponding with a target height had to be seen. The
target was considered visible to a vehicle’s rear parking sensor system if a visual or auditory warning was
provided. If the target was detected by the vehicle’s rear parking sensor system at a given location, then
it was assumed that all three target heights were detectable at that location. When making visibility
judgments using the mirrors, the observer was instructed to maintain a normal body position, keep his full
body weight against the seat pan and seat back, and keep his head centered in the head restraint. For
glances over the right shoulder, the observer was instructed to make a normal glance over the shoulder
and not to exaggerate his normal turning motion to increase visibility. Some vehicles’ backup camera
systems supported multiple viewing angles. Only the default view that was first available after the gear
selector was placed in reverse was assessed.
After completing the visibility measurements, researchers collected information to assess the
image quality of the backup camera display. A target 32 inches tall and 12 inches wide was placed 20
feet behind the rear bumper. The target was centered at the vehicle’s centerline. A measurement tape
6
was placed across the backup camera display and a photograph was taken for later analysis of the
backup camera image (see Figure 3). Researchers also measured the distance from the midpoint
between the observer’s eyes to the center of the backup camera display. The height and width of the
display also was recorded along with the visual and auditory warning characteristics of the parking sensor
system, if equipped.
Dependent Measures
Several measures were used to characterize the rear visibility of each vehicle. The first measure
was blind zone, defined as the area of the measurement field where a specific target height was not
visible using a single field of view or multiple fields of view. Blind zone without technology and blind zone
with technology was calculated for each vehicle. Blind zone without technology was the area not visible
using the left and right side mirrors, the rearview mirror, and glances over the right shoulder. Blind zone
with technology indicated the area not visible using the mirrors, glances over the right shoulder, backup
cameras, and not detected by parking sensors (if equipped). Visibility maps showing the individual
contribution of each field of view for the three target heights for al 21 vehicles can be found in the
Appendix.
Average minimum sight distance without and with technology also was calculated for each
vehicle. Minimum sight distance was the longitudinal distance from the rear bumper of the vehicle to the
first of at least two consecutive 1- by 1-foot squares where the target was visible or detected by parking
sensors for vehicles with this system. Minimum sight distance was recorded at 1-foot increments laterally
across an 8-foot span along the rear of each vehicle — 4 feet to the left and right of the vehicle’s
centerline. The average minimum sight distance was the mean of these eight values. If the target was
not visible or detected anywhere in the measurement field, then the maximum distance in the
measurement field was recorded (i.e., 70 feet) as the average minimum sight distance. The image size
for each backup camera display was assessed by calculating the subtended visual angle of the target.
This procedure was similar to that used by Mazzae and Garrott (2011) and the proposed procedure to
test image size in the recent proposed rulemaking (Office of the Federal Register, 2010). The primary
difference between the current effort and previous work is that the subtended visual angle was only
calculated for a single object behind the vehicle instead of multiple objects.
Subtended visual angle was calculated by combining information about the distance from the
midpoint between the observer’s eyes to the display with the width of the visual target in the backup
camera display. First, a scaling factor was calculated to determine the number of pixels per inch for each
photograph of a backup camera display. The X and Y pixel coordinates were recorded for the start point
and end point of a 2-inch section of the measurement tape across the camera display. The Euclidean
distance between these two points was the scaling factor. Next, the pixel coordinates at the left and right
edges of the target in the display were recorded. This distance, the scaling factor, and the distance from
7
the display to the midpoint between the observer’s eyes were used to calculate the subtended visual
angle of the target using formula 1.
-1
Θi = sin (pi / (di * si))
(1)
Formula 1 states the subtended visual angle of the target for a given display i in radians (Θi) is
equal to the inverse sine of the quotient produced by dividing the width of the target object in pixels (pi) by
the product of the distance from the midpoint between the observer’s eyes to the center of the backup
camera display (di) and the scaling factor (si). The subtended visual angle then was transformed from
radians to minutes of arc to compare with requirements proposed in NHTSA’s rear visibility test procedure
(Office of the Federal Register, 2010). A photograph of each vehicle’s backup camera display can be
found in the Appendix.
RESULTS
Rear Visibility without Technology
The blind zone for each vehicle and average minimum sight distance without technology and with
technology was calculated to characterize rear visibility for each target height. This section describes the
results for blind zone and sight distance without technology (Table 3). The average blind zone for the
2
30.2-inch tall object (240.24 ft ) across all vehicles was twice as large as the average blind zone for the
2
42.7-inch tall object (116.67 ft ). The Acura MDX had the largest blind zone for the 30.2-inch tall target
2
(360 ft ), and the Cadillac Escalade had the largest blind zone for the 36.8- and 42.7-inch tall targets (241
2
and 171 ft , respectively). The Ford Focus had the smallest blind zone for each target height.
The average minimum sight distance for a 30.2-inch tall object (27.3 feet) was more than twice as
long as the average distance for a 42.7-inch tall object (13.2 feet) (Table 3). The Audi A6 had the
shortest average minimum rear sight distance for the 30.2-, 36.8-, and 42.7-inch tall targets among all
vehicles in the sample (15.5, 9.9, and 5.5 feet, respectively). Average minimum sight distance for the
30.2- and 36.8-inch tall targets was longest for the Mazda CX-9 (41.3 and 32.6 feet), and the GMC
Acadia had the longest sight distance for the 42.7-inch tall target (19.5 feet).
Figures 4 and 5 show the average blind zone and minimum rear sight distance by vehicle class
for each target height. Average blind zone and average sight distance for each vehicle class decreased
as target height increased. The smallest blind zone and average sight distance for each target height
was observed among small cars. Large SUVs had the largest blind zone and average sight distance for
each target height, followed closely by midsize SUVs.
Benefits of Cameras and Sensors
Table 4 shows the blind zone and average minimum sight distance for the three target heights
using indirect glances, direct glances, and backing technology. The average blind zone with technology
2
across all vehicles was 21.5, 15.4, and 13 ft for the 30.2-, 36.8-, and 42.7-inch tall target heights,
8
respectively. The average minimum sight distance to each target across the entire vehicle sample was
1.1 feet or less. The Ford Focus and Ford F-150 did not have a blind zone behind the rear bumper for
any target height after including the areas visible using technology. After including technology, there was
no blind zone for the Chevy Equinox with the 36.8- and 42.7-inch tall targets and for the GMC Acadia with
the 42.7-inch tall target. The Mercedes GLK had the largest blind zone after including technology for
each target height. Average minimum sight distance after including technology was less than 2 feet for
every vehicle.
Figure 6 shows the average blind zone with backing technology by vehicle class for each target
height. Pickups had the smallest blind zone for each target height after including technology. Small cars
had the second smallest blind zone for the 30.2- and 36.8-inch tall targets, and large SUVs had the
second smallest blind zone for the 42.7-inch target height. The largest blind zone with technology was
observed for minivans. The 30.2-, 36.8-, and 42.7-inch tall targets were not visible for minivans in an
2
average area of 30.5, 21, and 20 ft , respectively.
Tables 5A and 5B show the reduction in blind zones due to increased visibility provided by
backup cameras, detection of non-visible areas by parking sensors, and the combination of these
technologies for all 21 vehicles. On average, backing technology reduced the blind zone by 91 percent
for the 30.2- and 36.8-inch tall target heights and 88 percent for the 42.7-inch tall target height. The
technology provided the least reduction in blind zone for the 30.2-, 36.8- and 42.7-inch tall targets for the
Ford Escape (83 percent), Mercedes E class (82.6 percent), and Chevrolet Cruze (76.3 percent),
respectively.
Eight vehicles were equipped with a backup camera system and a parking sensor system.
Among these eight vehicles, the average percent reduction in blind zone for each target height provided
by backup camera systems was 2-8 times larger than the percent reduction in blind zone provided by
parking sensor systems alone. Backup cameras reduced blind zone by 72-99 percent, and parking
sensor systems reduced blind zone by 12-48 percent. The area detected by parking sensor systems was
not completely redundant with the area visible using backup cameras. For vehicles with a parking sensor
and backup camera system, the average percent reduction in blind zone was 2-3 percentage points
greater when using both technologies compared with reductions provided by backup camera system
alone.
Backup Camera Display Image Size
Table 6 lists the display characteristics of each vehicle’s backup camera display and warning
characteristics of the rear parking sensor system (if equipped). In 19 of the vehicles, the backup camera
display was located in the center console and in two vehicles it was inset in the rearview mirror. Every
display in the center console was 6-8 inches wide except for the 5-inch wide display in the Honda CRV.
The two rearview mirror displays were smaller than the center console displays and measured just more
than 3 inches wide.
9
The average distance from the midpoint between the eyes of a 50th percentile male observer to
the display across all 21 vehicles was 31.1 inches. The shortest distance was observed in the Toyota
Tundra (23.7 inches) and the longest in the Honda CRV (39.8 inches). The distance from the midpoint of
the observer’s eyes to the display was used to calculate the subtended visual angle of a 12-inch wide
target viewed by the observer in the display. The average visual angle across all vehicles was 12.9
minutes of arc. The largest visual angle was observed in the Mercedes E class (17.5 minutes of arc) and
the smallest visual angle was observed in the Honda CRV (5 minutes of arc). The visual angle was less
than 10 minutes of arc for three vehicle displays, 10-14.9 minutes of arc for 15 vehicle displays, and 15
minutes of arc or greater for three vehicle displays.
Eight vehicles in this study were equipped with rear parking sensor systems. Each had a graded
auditory warning that increased in pulse rate as the target object moved closer to the rear bumper. Six of
the eight systems also had graded visual warnings that provided distance and location information for the
target relative to the vehicle’s rear bumper. Three of these vehicles provided this information using a
schematic of the vehicle, and the other three overlaid this information on the backup camera display. The
Ford Focus and Ford F-150’s rear parking sensor systems only provided auditory warnings.
DISCUSSION
Adequate visibility around and behind the vehicle is necessary for the driver to maintain
awareness of the vehicle’s surroundings and to reduce the probability of a reversing vehicle striking or
running over objects. Previous studies have characterized rear visibility for an object simulating the
height of a 1-2-year-old child, but older, taller children also are frequently involved in backover crashes
(Nhan et al., 2009). This study characterized rear visibility for a 12-15-, 30-36-, and 60-72-month-old
child-size object in 21 vehicles and evaluated how backup cameras and parking sensors improve visibility
for children of these ages.
As expected, taller children were more visible than shorter children. The blind zone for a 12-15month-old child-size object was, on average, more than twice as large as it was for a 60-72-month-old
child-size object. On average, a 12-15-month-old child-size object was not visible to a 50th percentile
male driver within about 27 feet of the rear bumper. A recent naturalistic study of backing maneuvers
found that the average backing distance out of a parking space was 21 feet (Mazzae & Barickman, 2008);
a 12-15-month-old child would never be visible during such a maneuver. Although visibility for a 60-72month-old child-size object was better than for a 12-15-month-old child-size object, on average, a 60-72month-old child-size object was not visible to a 50th percentile male driver up to about 13 feet behind rear
bumper. Mazzae and Garrott (2011) estimated that the risk of backing into a pedestrian was greatest
when the pedestrian starts within 15 feet directly behind the rear bumper. Based on the current results,
children younger than 7 are not easily seen in this area and would be at high risk for being struck by a
reversing vehicle.
10
Consistent with previous research, larger vehicles typically had poorer rear visibility for child-size
objects than smaller vehicles (Consumer Reports, 2012; Mazzae & Barickman 2009; Mazzae & Garrott
2008). On average, large SUVs had the largest blind zones and longest average minimum sight
distances among all vehicle classes. Small cars had the smallest blind zones and shortest minimum sight
distances. Average rear visibility in minivans and pickup trucks was better than in SUVs even though
minivans and pickup trucks are over-represented in backover crashes with pediatric injury. Pinkney et al.
(2006) found that children younger than 10 were significantly more likely to be injured in a driveway
backover crash involving a pickup truck or minivan compared with a passenger car, but the likelihood for
pickups and SUVs was similar. The Pinkney et al. study was based on police crash reports from 1998 to
2003, so the vehicles in that study were much older than the ones measured in the current study.
Differences in rear visibility among newer vehicles observed in the current study may differ substantially
from the differences among the vehicles in Pinkney et al.
In the current study, rear visibility was not always worse in larger vehicles compared with smaller
ones. As illustrated in Figure 7, the blind zone for a 30.2-inch tall object in the Hyundai Sonata (midsize
car) extended beyond the blind zone in the Ford F-150 (pickup truck). The Sonata had an extremely
sloped rear window and tall rear trunk lid that limited visibility directly behind the vehicle. Although the
dimensions of the F-150 were larger than in the Sonata, the F-150 had large side mirrors with auxiliary
mirrors that increased visibility behind the vehicle and made up for its larger size.
An extremely sloped rear window and tall rear trunk lid also reduced visibility behind the rear
bumper of the Infiniti M37 (Figure 8). The blind zone for the 30.2-inch tall object in the Infiniti M37 (large
car) was slightly greater than the larger Dodge Grand Caravan (minivan), and the average minimum sight
distance also was about 6 feet longer. These two examples illustrate how design features can restrict
rear visibility. Highly sloped rear windows and taller rear trunk lids are intended to make the vehicle
aerodynamic but decrease the area visible through the rear window. Large rear head restraints and large
B- and C-pillars also impacted rear visibility of vehicles in this study. Auto manufacturers should consider
eliminating or reducing the size of vehicle design features that block large rear areas from unassisted
views in addition to installing technology to enhance rear visibility.
A number of manufacturers are installing backup cameras to improve rear visibility and parking
sensors to detect objects in areas near the rear of the vehicle that are not visible. The results from the
current study illustrate the large improvements in visibility and detection of objects behind the vehicle
provided by these technologies. Across all vehicles, backing technologies reduced the blind zone by
about 90 percent for each target height. They also nearly eliminated the differences in blind zones
observed among different vehicle classes. For example, on average, the blind zone for large SUVs was
2
141.5 ft larger than the area for small cars for the shortest target height; however, the difference was
2
only 5 ft when factoring in technology. Enhancements in rear visibility and detection of objects behind
the vehicle provided by backing technologies can help prevent property-damage only collisions where a
vehicle reverses into a fixed object. They also can help drivers avoid backing into another vehicle, which
11
can lead to costly repairs especially if the bumpers of the two vehicles are not compatible and do not line
up (IIHS, 2010). Most important, backup cameras and parking sensors enhance visibility and detection of
objects in the area directly behind the vehicle where pedestrian backover crash risk is the highest
(Mazzae & Garrott, 2011). When examined for a span 4 feet to the left and 4 feet to the right of the
vehicle center line, average minimum sight distance was less than 2 feet for every vehicle after including
the areas visible with technology.
Increases in rear visibility provided by backup cameras were greater than areas detected by
parking sensors that were not visible using other fields of view. Across all target heights, backup
cameras reduced the blind zone by 72-99 percent compared with 12-48 percent reductions observed for
parking sensors. However, the areas detected by parking sensors were not always visible using backup
cameras. The average percent reduction in blind zone for the eight vehicles with a backup camera and
parking sensors was 93-94 percent. The percent reduction in blind zone was 90-92 percent for these
eight vehicles when only including the additional areas visible using the camera. Two to three percentage
points is not a dramatic functional increase in rear visibility, but it is of practical importance. Parking
sensors detect objects near the rear of the vehicle where backover crash risk is greatest. Plus, the
alerting function of the sensor systems can draw drivers’ attention to potential hazards.
Technology can provide drivers with a more comprehensive view behind the vehicle, but these
technologies may not completely eliminate backing crashes. Studies show that while cameras and
parking sensors significantly increase the likelihood of avoiding an unexpected obstacle behind the
vehicle, they do not prevent all backing crashes (e.g., Kim et al., 2012; Llaneras et al., 2011; Mazzae,
2010). Drivers may not look at the backup camera display at the appropriate time to prevent a collision,
or they may not look at the display at all when reversing (e.g., Mazzae & Barickman, 2008). They also
may ignore or disable parking sensors if the system is prone to false alarms (e.g., Llaneras et al., 2011),
or reverse too quickly so as to exceed the functional capability of the system (Llaneras et al., 2005).
Backing crashes still can occur in vehicles with both backup cameras and parking sensors, and there is
some evidence that the combination of these systems may not perform as well as a backup camera alone
(Mazzae, 2010).
One possible solution for preventing backing crashes is to have the vehicle intervene on behalf of
the driver by automatically applying the brakes when a possible collision is detected. Kochhar et al.
(2012) examined driver responses to a reverse braking aid that issued an auditory warning and applied
the brakes to stop the vehicle. All the drivers put their foot on the brake pedal after automatic braking
occurred in the presence of an obstacle behind the vehicle, and half looked immediately at the camera
display following the braking intervention. Preliminary evaluations of frontal collision avoidance systems,
systems that intervene autonomously rather than relying on driver intervention, indicate autonomous
interventions may prove to be more effective at mitigating frontal collisions than warning systems alone
(IIHS, 2012). Autonomous braking backup systems might prove similarly more effective at reducing the
12
risk of backover crashes than systems that display the area behind the vehicle or sensor systems that
alert drivers of potential hazards behind the vehicle.
To reduce backover crashes, NHTSA has proposed rulemaking to enhance the rear visibility of
passenger vehicles. Backup cameras currently are the only technology that will meet the proposed
requirements. The size of the image displayed may influence the use of backup camera displays to
detect obstacles behind the vehicle. With small displays, drivers may have trouble interpreting or
identifying images. Satoh et al. (1983) found that subjective judgments of image visibility using a
periscope mirror system were not possible for images with a subtended visual angle less than 5 minutes
of arc. Based on this work, NHTSA’s proposal would require the visual angle of three objects located 20
feet behind the vehicle to each exceed 3 minutes of arc and the average visual angle of these objects to
exceed 5 minutes of arc. The visual angle measured in every vehicle in the current study exceeded 3
minutes of arc and all but one vehicle exceeded 5 minutes of arc (Honda CRV). The CRV display was
among the smallest of all the study vehicles and positioned the farthest from the midpoint between a 50th
percentile male driver’s eyes. It is unclear if the Honda CRV’s smaller image would lead to significant
differences in object identification and collision avoidance compared with larger displays like that in the
Ford Escape (16.5 minutes of arc). This should be a topic for future research. However, in general, the
backup cameras in many of the study vehicles easily surpassed the proposed requirements for image
size.
One limitation of the study was that the vehicle sample was small. The results across vehicle
classes may not accurately reflect the relative rear visibility of all the 2010-13 model year vehicles in
different vehicle classes. However, it is worth noting that the patterns of results in this study are
consistent with other recent studies of rear visibility and studies of backover crash risk (Consumer
Reports, 2012; Mazzae & Garrott, 2008; Mazzae & Barickman, 2009).
Another limitation of the current study is that it relied on two human observers to make visibility
judgments. It is unlikely that the two observers had identical body motions and glances or even that
either observer had the same body motions and glances across the study trials. Although similar, the
body dimensions of the observers were not identical, and body dimensions like height are known to
influence rear visibility (Consumer Reports, 2012). A pilot study of three vehicles provided strong
evidence of high inter-observer reliability between the observers, suggesting their observations were
consistent with one another despite differences in body dimensions. The only field of view where interobserver reliability was an issue was for glances over the right shoulder. Observer DK had a limited
range of neck motion, which affected his ability to completely turn his head over his right shoulder.
In conclusion, the results showed that rear visibility typically is worse in larger vehicles compared
with smaller vehicles, but there were exceptions to this general pattern. A taller object simulating the
height of a 60-72-month-old child was easier to see than a smaller object simulating a 12-15-month-old
child, but the taller object still was not visible up to 13 feet behind the rear bumper. Backup cameras
nearly eliminated the blind zone behind vehicles, and parking sensors provided information that further
13
enhanced awareness of objects behind the vehicle. Hence, backup cameras, as well as the combination
of backup cameras and parking sensors, have the potential to substantially decrease the estimated
18,000 injuries and 292 fatalities that occur annually in backover crashes if drivers use the technology
appropriately.
ACKNOWLEDGEMENTS
The authors would like to thank all of the individuals at the Insurance Institute for Highway Safety
who helped obtain the vehicles, prepare vehicles for measurement, set up the measurement field, and
assisted with data collection. We express our gratitude to dealerships in the local Charlottesville, Virginia,
area for cooperating with us on this study. We especially want to thank Troy Vann and Dan Kellerman for
making visibility judgments. This work was supported by the Insurance Institute for Highway Safety.
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16
Table 1
Dimensions, available backing technology, and observer for each vehicle.
Backing technology
Rear
Backup
parking
camera
sensor
x
x
x
2013 Chevrolet Cruze 4dr
2012 Ford Focus 5dr
Dimensions (in.)
Length
Width
Height
181.0
70.7
58.1
171.6
71.8
57.7
Midsize car
2013 Honda Accord 4dr
2013 Hyundai Sonata 4dr
2012 Toyota Camry 4dr
191.4
189.8
189.2
72.8
72.2
71.7
57.7
57.9
57.9
x
x
x
Large car
2012 Audi A6 Quattro 4dr 4WD
2012 Infiniti M37 4dr 2WD
2011 Mercedes E Class 4 dr 2WD
193.9
194.7
191.7
73.7
72.6
75.9
57.8
59.1
57.9
x
x
x
Small SUV
2013 Ford Escape 4 dr 4WD
2013 Honda CR-V 4dr 2WD
178.1
178.3
72.4
71.6
66.3
64.7
x
x
Midsize SUV
2011 Acura MDX 4 dr 4WD
2013 Chevrolet Equinox 4dr 4WD
2012 Mazda CX-9 4dr 4WD
2013 Mercedes GLK Class 4WD
2012 Toyota 4Runner 4WD
191.6
187.8
200.2
178.3
189.9
78.5
72.5
76.2
74.3
75.8
68.2
66.3
68.0
66.9
71.5
x
x
x
x
x
Large SUV
2013 Cadillac Escalade 4dr 4WD
2012 GMC Acadia 4WD
202.5
200.7
79.0
78.2
75.9
72.8
x
x
x
x
DK
TV
Minivan
2013 Dodge Grand Caravan 2WD
2010 Honda Odyssey
202.8
202.1
78.7
77.1
67.9
68.8
x
x
x
x
DK
DK
Large pickup
2012 Ford F-150 Super Cab Pickup 4x4
2012 Toyota Tundra CrewMax 4WD
243.9
228.7
79.2
79.9
79.2
76.0
x
x
x
DK
TV
Vehicle
Small car
Table 2
Stature and seated height of candidate observers and a 50th percentile male.
Observer
Stature (in.)
Seated eye height (in.)
TV*
70.5
33.8
DK*
69.7
31.8
JS
69.1
32.3
DP
69.1
31.8
50th percentile male
69.1
31.2
*Observers used in the full study
17
Observer
DK
DK
TV
DK
TV
x
TV
TV
DK
DK
TV
x
DK
DK
TV
DK
DK
Table 3
Blind zone and average minimum sight distance without backing technology as a function of target height.
Average minimum
Blind zone (ft2)
sight distance (ft)
Target height (in.)
Target height (in.)
Vehicle
30.2
36.8
42.7
30.2
36.8
42.7
Small car
Chevrolet Cruze
230
157
97
24.1
15.3
8.1
Ford Focus
118
80
50
15.5
10.8
7.0
Class mean
174
118.5
73.5
19.8
13.0
7.6
Midsize car
Honda Accord
Hyundai Sonata
Toyota Camry
Class mean
175
263
201
213
105
187
147
146.33
57
121
97
91.67
18.4
30.3
20.4
23.0
12.0
21.0
14.8
15.9
6.1
13.4
8.6
9.4
Large car
Audi A6
Infiniti M37
Mercedes E class
Class mean
138
265
191
198
89
193
132
138
54
120
76
83.33
15.5
31.3
22.6
23.1
9.9
22.9
15.3
16.0
5.5
13.8
7.3
8.8
Small SUV
Ford Escape
Honda CRV
Class mean
223
264
243.5
158
190
174
111
130
120.5
24.5
30.0
27.3
17.9
22.5
20.2
12.4
15.1
13.8
Midsize SUV
Acura MDX
Chevrolet Equinox
Mazda CX-9
Mercedes GLK
Toyota 4Runner
Class mean
360
277
323
279
239
295.6
226
200
236
203
158
204.6
156
131
151
148
96
136.4
38.1
34.3
41.3
25.8
26.4
33.2
25.6
25.8
32.6
18.5
16.8
23.9
17.9
17
18.8
12.6
11.5
15.6
Large SUV
Cadillac Escalade
GMC Acadia
Class mean
326
305
315.5
241
226
233.5
171
153
162
32.5
38.6
35.6
26.0
29.0
27.5
19.1
19.5
19.3
Minivan
Dodge Grand Caravan
Honda Odyssey
Class mean
238
242
240
181
172
176.5
148
118
133
25.1
29.1
27.1
18.3
21.0
19.6
14.6
14.4
14.5
Large pickup
Ford F-150
Toyota Tundra
Class mean
185
203
194
169
170
169.5
140
125
132.5
23.8
25.3
24.5
21.9
21.5
21.7
18.3
15.9
17.1
240.24
172.38
116.67
27.3
20.0
13.2
Overall mean
18
Table 4
Blind zone and average minimum sight distance with backing technology as a function of target height.
Blind zone
Average minimum
with technology (ft2)
sight distance (ft)
Target height (in.)
Target height (in.)
Vehicle
30.2
36.8
42.7
30.2
36.8
42.7
Small car
Chevrolet Cruze
29
26
23
1.1
≤1
≤1
Ford Focus
0
0
0
≤1
≤1
≤1
Class mean
14.5
13
11.5
≤1
≤1
≤1
Midsize car
Honda Accord
Hyundai Sonata
Toyota Camry
Class mean
18
27
29
24.67
14
25
20
19.67
13
21
19
17.67
1.3
1.3
1.1
1.2
≤1
1.3
1.1
1.1
≤1
1.3
1.1
1.1
Large car
Audi A6
Infiniti M37
Mercedes E class
Class mean
14
19
23
18.67
11
16
23
16.67
11
16
17
14.67
≤1
≤1
1.8
1.2
≤1
≤1
1.8
1.2
≤1
≤1
1.4
≤1
Small SUV
Ford Escape
Honda CRV
Class mean
38
22
30
22
12
17
19
11
15
1.8
≤1
1.4
≤1
≤1
≤1
≤1
≤1
≤1
Midsize SUV
Acura MDX
Chevrolet Equinox
Mazda CX-9
Mercedes GLK
Toyota 4Runner
Class mean
31
9
17
42
24
24.6
16
0
14
30
18
15.6
14
0
9
28
12
12.6
1.3
≤1
1.5
1.5
1.4
1.3
≤1
≤1
1.5
1.3
1.1
1.2
≤1
≤1
≤1
1.3
≤1
≤1
Large SUV
Cadillac Escalade
GMC Acadia
Class mean
36
3
19.5
28
1
14.5
14
0
7
≤1
≤1
≤1
≤1
≤1
≤1
≤1
≤1
≤1
Minivan
Dodge Grand Caravan
Honda Odyssey
Class mean
32
29
30.5
26
16
21
26
14
20
≤1
≤1
≤1
≤1
≤1
≤1
≤1
≤1
≤1
Large pickup
Ford F-150
Toyota Tundra
Class mean
0
9
4.5
0
6
3
0
5
2.5
≤1
≤1
≤1
≤1
≤1
≤1
≤1
≤1
≤1
21.5
15.4
13.0
1.1
≤1
≤1
Overall mean
19
Table 5A
Blind zone with different combinations of backing technologies.
Blind zone without
technology (ft2)
Target height (in.)
Vehicle
30.2
36.8
42.7
Small car
Chevrolet Cruze
230
157
97
Ford Focus
118
80
50
Class mean
174.0
118.5
73.5
Blind zone including
parking sensors only (ft2)
Target height (in.)
30.2
36.8
42.7
—
—
—
94
56
26
94.0
56.0
26.0
Blind zone including
backup camera only (ft2)
Target height (in.)
30.2
36.8
42.7
29
26
23
4
4
4
16.5
15.0
13.5
Blind zone with all
backing technologies (ft2)
Target height (in.)
30.2
36.8
42.7
29
26
23
0
0
0
14.5
13.0
11.5
Midsize car
Honda Accord
Hyundai Sonata
Toyota Camry
Class mean
175
263
201
213.0
105
187
147
146.3
57
121
97
91.7
—
—
—
—
—
—
—
—
—
—
—
—
18
27
29
24.7
14
25
20
19.7
13
21
19
17.7
18
27
29
24.7
14
25
20
19.7
13
21
19
17.7
Large car
Audi A6
Infiniti M37
Mercedes E class
Class mean
138
265
191
198.0
89
193
132
138.0
54
120
76
83.3
106
—
—
106.0
57
—
—
57.0
28
—
—
28.0
18
19
23
20.0
15
16
23
18.0
15
16
17
16.0
14
19
23
18.7
11
16
23
16.7
11
16
17
14.7
Small SUV
Ford Escape
Honda CRV
Class mean
223
264
243.5
158
190
174.0
111
130
120.5
—
—
—
—
—
—
—
—
—
38
22
30.0
22
12
17.0
19
11
15.0
38
22
30.0
22
12
17.0
19
11
15.0
Midsize SUV
Acura MDX
Chevrolet Equinox
Maxda CX-9
Mercedes GLK
Toyota 4Runner
Class mean
360
277
323
279
239
295.6
226
200
236
203
158
204.6
156
131
151
148
96
136.4
—
244
—
—
—
244.0
—
170
—
—
—
170.0
102
—
—
—
102.0
31
14
17
42
24
25.6
16
3
14
30
18
16.2
14
2
9
28
12
13.0
31
9
17
42
24
24.6
16
0
14
30
18
15.6
14
0
9
28
12
12.6
Large SUV
Cadillac Escalade
GMC Acadia
Class mean
326
305
315.5
241
226
233.5
171
153
162.0
274
263
268.5
193
184
188.5
135
117
126.0
41
4
22.5
33
2
17.5
15
1
8.0
36
3
19.5
28
1
14.5
14
0
7.0
Minivan
Dodge Grand Caravan
Honda Odyssey
Class mean
238
242
240.0
181
172
176.5
148
118
133.0
201
208
204.5
151
142
146.5
118
88
103.0
38
33
35.5
29
18
23.5
29
16
22.5
32
29
30.5
26
16
21.0
26
14
20.0
Large pickup
Ford F-150
Toyota Tundra
Class mean
185
203
194.0
169
170
169.5
140
125
132.5
149
133
104
149.0
133.0
104.0
2
9
5.5
2
6
4.0
2
5
3.5
0
9
4.5
0
6
3.0
0
5
2.5
240.2
172.4
116.7
192.4
135.8
89.8
23.0
16.6
13.9
21.5
15.4
13.0
Overall mean
20
Table 5B
Blind zone with different combinations of backing technologies and the percent reduction in blind zone provided by each.
Percent reduction in blind
Percent reduction in blind
Percent reduction in blind
zone provided by parking
zone provided by backup
zone provided by both
sensor system alone
camera alone
technologies combined
Target height (in.)
Target height (in.)
Target height (in.)
Vehicle
30.2
36.8
42.7
30.2
36.8
42.7
30.2
36.8
42.7
Small car
Chevrolet Cruze
—
—
—
87.4
83.4
79.3
87.4
83.4
79.3
Ford Focus
20.3
30.0
48.0
96.6
95.0
92.0
100.0
100.0
100.0
Class mean
20.3
30.0
48.0
92.0
89.2
85.7
93.7
91.7
89.7
Midsize car
Honda Accord
Hyundai Sonata
Toyota Camry
Class mean
—
—
—
—
—
—
—
—
—
—
—
—
89.7
89.7
85.6
88.3
86.7
86.6
86.4
86.6
77.2
82.6
80.4
80.1
89.7
89.7
85.6
88.3
86.7
86.6
86.4
86.6
77.2
82.6
80.4
80.1
Large car
Audi A6
Infiniti M37
Mercedes E class
Class mean
23.2
—
—
23.2
36.0
—
—
36.0
48.1
—
—
48.1
87.0
92.8
88.0
89.3
83.1
91.7
82.6
85.8
72.2
86.7
77.6
78.8
89.9
92.8
88.0
90.2
87.6
91.7
82.6
87.3
79.6
86.7
77.6
81.3
Small SUV
Ford Escape
Honda CRV
Class mean
—
—
—
—
—
—
—
—
—
83.0
91.7
87.4
86.1
93.7
89.9
82.9
91.5
87.2
83.0
91.7
87.4
86.1
93.7
89.9
82.9
91.5
87.2
Midsize SUV
Acura MDX
Chevrolet Equinox
Maxda CX-9
Mercedes GLK
Toyota 4Runner
Class mean
11.9
—
—
—
11.9
15.0
—
—
—
15.0
22.1
—
—
—
22.1
91.4
94.9
94.7
84.9
90.0
91.2
92.9
98.5
94.1
85.2
88.6
91.9
91.0
98.5
94.0
81.1
87.5
90.4
91.4
96.8
94.7
84.9
90.0
91.6
92.9
100.0
94.1
85.2
88.6
92.2
91.0
100.0
94.0
81.1
87.5
90.7
Large SUV
Cadillac Escalade
GMC Acadia
Class mean
16.0
13.8
14.9
19.9
18.6
19.3
21.1
23.5
22.3
87.4
98.7
93.1
86.3
99.1
92.7
91.2
99.3
95.3
89.0
99.0
94.0
88.4
99.6
94.0
91.8
100.0
95.9
Minivan
Dodge Grand Caravan
Honda Odyssey
Class mean
15.5
14.0
14.8
16.6
17.4
17.0
20.3
25.4
22.8
84.0
86.4
85.2
84.0
89.5
86.8
80.4
86.4
83.4
86.6
88.0
87.3
85.6
90.7
85.3
82.4
88.1
81.5
Large pickup
Ford F-150
Toyota Tundra
Class mean
19.5
21.3
25.7
19.5
21.3
25.7
98.9
95.6
97.3
98.8
96.5
97.7
98.6
96.0
97.3
100.0
95.6
97.8
100.0
96.5
98.3
100.0
96.0
98.0
16.8
21.8
29.3
90.4
89.9
87.0
91.1
90.8
88.1
Overall mean
21
Table 6
Backup camera display characteristics and rear parking sensor system warning characteristics.
Backup camera
Distance
Visual angle of
Display
from eye to
12-inch wide target
Vehicle
Display location
size (in.)
display (in.)
(minutes of arc)
Small car
Chevrolet Cruze
Center console
7
32.5
15.4
Ford Focus
Center console
8
30.0
14.1
Rear parking sensor system
Auditory warning
Visual warning
—
—
Graded, pulse rate increased
—
when object was closer
Midsize car
Honda Accord
Hyundai Sonata
Toyota Camry
Center console
Center console
Center console
8
7
6.1
35.5
30.3
29.1
11.7
13.8
13.4
—
—
—
—
—
—
Large car
Audi A6
Center console
8
31.2
14.3
Graded, pulse rate increased
when object was closer
Infiniti M37
Mercedes E class
Center console
Center console
8.0
7
31.1
30.9
14.3
17.5
—
—
Graded color scheme (red imminent, yellow
cautionary); schematic of vehicle with
distance and location specific information
—
—
Small SUV
Ford Escape
Honda CRV
Center console
Center console
8
5
31.0
39.8
16.5
5.0
—
—
—
—
Midsize SUV
Acura MDX
Chevrolet Equinox
Center console
Center console
8
7
39.0
33.0
11.1
14.1
—
Graded, pulse rate increased
when object was closer
Mazda CX-9
Mercedes GLK
Toyota 4Runner
Center console
Center console
Center console
7
7
6.1
30.6
29.9
31.0
13.8
12.4
13.7
—
—
—
—
Graded color scheme (red imminent, yellow
cautionary); distance and location specific
cues overlaid on backup camera image
—
—
—
Cadillac Escalade
Center console
8
32.8
13.2
Graded, pulse rate increased
when object was closer
GMC Acadia
Center console
6.5
30.8
13.3
Graded, pulse rate increased
when object was closer
Dodge Grand Caravan
Center console
6.5
29.9
12.2
Honda Odyssey
Center console
8
33.5
14.3
Graded, pulse rate increased
when object was closer
Graded, pulse rate increased
when object was closer
Schematic of vehicle with distance
and location specific information
Text cue and schematic of vehicle with
distance and location specific information
Ford F-150
Rearview mirror
3.3
24.4
7.9
—
Toyota Tundra
Rearview mirror
3.2
23.7
8.0
Graded, pulse rate increased
when object was closer
—
Large SUV
Minivan
Large pickup
22
Graded color scheme (red imminent, yellow
cautionary); distance and location specific
cues overlaid on backup camera image
Graded color scheme (red imminent, yellow
cautionary); distance and location specific
cues overlaid on backup camera image
—
(a)
(b)
Figure 1. (a) Visual target and (b) dimensions
Figure 2. Measurement field, 20 by 75 feet
23
Figure 3. Example backup camera display with target to evaluate image size
350
Target height
300
30.2"
36.8"
Blind zone area (ft2)
250
42.7"
200
150
100
50
0
Small car
Midsize car
Large car
Small SUV Midsize SUV Large SUV
Figure 4. Blind zone as a function of target height for different vehicle classes.
24
Minivan
Large pickup
40
Target height
Average minimum sight distance (ft)
35
30.2"
36.8"
30
42.7"
25
20
15
10
5
0
Small car
Midsize car
Large car
Small SUV Midsize SUV Large SUV
Minivan
Large pickup
Figure 5. Average minimum sight distance as a function of target height for different vehicle classes.
40
Target height
35
30.2"
36.8"
Blind zone area (ft2)
30
42.7"
25
20
15
10
5
0
Small car
Midsize car
Large car
Small SUV Midsize SUV Large SUV
Minivan
Large pickup
Figure 6. Blind zone with backing technology for different vehicle classes as a function of target height.
25
Figure 7. Blind zone for a 30.2-inch tall object in the Hyundai Sonata (orange) and Ford F-150 (purple).
Figure 8. Blind zone for a 30.2-inch tall object in the Infiniti M37 (blue) and Dodge Grand Caravan (brown).
26
APPENDIX
REAR VISIBILITY MAPS FOR EACH TARGET HEIGHT AND BACKUP CAMERA DISPLAY IMAGE
FOR EACH VEHICLE IN ALPHABETICAL ORDER
2011 Acura MDX 4 dr 4WD: Visibility map for 30.2-inch tall target
2011 Acura MDX 4 dr 4WD: Visibility map for 36.8-inch tall target
A-1
2011 Acura MDX 4 dr 4WD: Visibility map for 42.7-inch tall target
A-2
2011 Acura MDX 4 dr 4WD: Backup camera display
A-3
2012 Audi A6 Quattro 4dr 4WD: Visibility map for 30.2-inch tall target
2012 Audi A6 Quattro 4dr 4WD: Visibility map for 36.8-inch tall target
A-4
2012 Audi A6 Quattro 4dr 4WD: Visibility map for 42.7-inch tall target
A-5
2012 Audi A6 Quattro 4dr 4WD: Backup camera display
A-6
2013 Cadillac Escalade 4dr 4WD: Visibility map for 30.2-inch tall target
2013 Cadillac Escalade 4dr 4WD: Visibility map for 36.8-inch tall target
A-7
2013 Cadillac Escalade 4dr 4WD: Visibility map for 42.7-inch tall target
A-8
2013 Cadillac Escalade 4dr 4WD: Backup camera display
A-9
2013 Chevrolet Cruze 4dr: Visibility map for 30.2-inch tall target
2013 Chevrolet Cruze 4dr: Visibility map for 36.8-inch tall target
A-10
2013 Chevrolet Cruze 4dr: Visibility map for 42.7-inch tall target
A-11
2013 Chevrolet Cruze 4dr: Backup camera display
A-12
2013 Chevrolet Equinox 4dr 4WD: Visibility map for 30.2-inch tall target
2013 Chevrolet Equinox 4dr 4WD: Visibility map for 36.8-inch tall target
A-13
2013 Chevrolet Equinox 4dr 4WD: Visibility map for 42.7-inch tall target
A-14
2013 Chevrolet Equinox 4dr 4WD: Backup camera display
A-15
2013 Dodge Grand Caravan 2WD: Visibility map for 30.2-inch tall target
2013 Dodge Grand Caravan 2WD: Visibility map for 36.8-inch tall target
A-16
2013 Dodge Grand Caravan 2WD: Visibility map for 42.7-inch tall target
A-17
2013 Dodge Grand Caravan 2WD: Backup camera display
A-18
2013 Ford Escape 4 dr 4WD: Visibility map for 30.2-inch tall target
2013 Ford Escape 4 dr 4WD: Visibility map for 36.8-inch tall target
A-19
2013 Ford Escape 4 dr 4WD: Visibility map for 42.7-inch tall target
A-20
2013 Ford Escape 4 dr 4WD: Backup camera display
A-21
2012 Ford F150 super cab pickup 4x4: Visibility map for 30.2-inch tall target
2012 Ford F150 super cab pickup 4x4: Visibility map for 36.8-inch tall target
A-22
2012 Ford F150 super cab pickup 4x4: Visibility map for 42.7-inch tall target
A-23
2012 Ford F150 super cab pickup 4x4: Backup camera display
A-24
2012 Ford Focus 5dr: Visibility map for 30.2-inch tall target
2012 Ford Focus 5dr: Visibility map for 36.8-inch tall target
A-25
2012 Ford Focus 5dr: Visibility map for 42.7-inch tall target
A-26
2012 Ford Focus 5dr: Backup camera display
A-27
2012 GMC Acadia 4WD: Visibility map for 30.2-inch tall target
2012 GMC Acadia 4WD: Visibility map for 36.8-inch tall target
A-28
2012 GMC Acadia 4WD: Visibility map for 42.7-inch tall target
A-29
2012 GMC Acadia 4WD: Backup camera display
A-30
2013 Honda Accord 4dr: Visibility map for 30.2-inch tall target
2013 Honda Accord 4dr: Visibility map for 36.8-inch tall target
A-31
2013 Honda Accord 4dr: Visibility map for 42.7-inch tall target
A-32
2013 Honda Accord 4dr: Backup camera display
A-33
2013 Honda CR-V 4dr 2WD: Visibility map for 30.2-inch tall target
2013 Honda CR-V 4dr 2WD: Visibility map for 36.8-inch tall target
A-34
2013 Honda CR-V 4dr 2WD: Visibility map for 42.7-inch tall target
A-35
2013 Honda CR-V 4dr 2WD: Backup camera display
A-36
2010 Honda Odyssey: Visibility map for 30.2-inch tall target
2010 Honda Odyssey: Visibility map for 36.8-inch tall target
A-37
2010 Honda Odyssey: Visibility map for 42.7-inch tall target
A-38
2010 Honda Odyssey: Backup camera display
A-39
2013 Hyundai Sonata 4dr: Visibility map for 30.2-inch tall target
2013 Hyundai Sonata 4dr: Visibility map for 36.8-inch tall target
A-40
2013 Hyundai Sonata 4dr: Visibility map for 42.7-inch tall target
A-41
2013 Hyundai Sonata 4dr: Backup camera display
A-42
2012 Infiniti M37 4dr 2WD: Visibility map for 30.2-inch tall target
2012 Infiniti M37 4dr 2WD: Visibility map for 36.8-inch tall target
A-43
2012 Infiniti M37 4dr 2WD: Visibility map for 42.7-inch tall target
A-44
2012 Infiniti M37 4dr 2WD: Backup camera display
A-45
2012 Mazda CX-9 4dr 4WD: Visibility map for 30.2-inch tall target
2012 Mazda CX-9 4dr 4WD: Visibility map for 36.8-inch tall target
A-46
2012 Mazda CX-9 4dr 4WD: Visibility map for 42.7-inch tall target
A-47
2012 Mazda CX-9 4dr 4WD: Backup camera display
A-48
2011 Mercedes E class 4dr 2WD: Visibility map for 30.2-inch tall target
2011 Mercedes E class 4dr 2WD: Visibility map for 36.8-inch tall target
A-49
2011 Mercedes E class 4dr 2WD: Visibility map for 42.7-inch tall target
A-50
2011 Mercedes E class 4dr 2WD: Backup camera display
A-51
2013 Mercedes GLK class 4WD: Visibility map for 30.2-inch tall target
2013 Mercedes GLK class 4WD: Visibility map for 36.8-inch tall target
A-52
2013 Mercedes GLK class 4WD: Visibility map for 42.7-inch tall target
A-53
2013 Mercedes GLK class 4WD: Backup camera display
A-54
2012 Toyota 4Runner 4WD: Visibility map for 30.2-inch tall target
2012 Toyota 4Runner 4WD: Visibility map for 36.8-inch tall target
A-55
2012 Toyota 4Runner 4WD: Visibility map for 42.7-inch tall target
A-56
2012 Toyota 4Runner 4WD: Backup camera display
A-57
2012 Toyota Camry 4dr: Visibility map for 30.2-inch tall target
2012 Toyota Camry 4dr: Visibility map for 36.8-inch tall target
A-58
2012 Toyota Camry 4dr: Visibility map for 42.7-inch tall target
A-59
2012 Toyota Camry 4dr: Backup camera display
A-60
2012 Toyota Tundra CrewMax 4WD: Visibility map for 30.2-inch tall target
2012 Toyota Tundra CrewMax 4WD: Visibility map for 36.8-inch tall target
A-61
2012 Toyota Tundra CrewMax 4WD: Visibility map for 42.7-inch tall target
A-62
2012 Toyota Tundra CrewMax 4WD: Backup camera display
A-63