AN EVALUATION OF THE EFFECTIVENESS OF RED-LIGHT CAMERAS AT
SIGNALISED INTERSECTIONS
Alfred-Shalom Hakkert
Transportation Research Institute, Technion, Israel
1. INTRODUCTION
Crashes at intersections in general and at signalized intersections amongst
these, form a significant part of the safety picture in many countries. In the US, in
1999, some 1,347,000 crashes occurred at traffic signal controlled intersections
out of a total of 6,279,000 reported crashes (21 percent) (NHTSA, 2000). Of a
total 2,054,000 reported injury crashes in the US in 1999, 476,000 occurred at
signalized intersections (23 percent) indicating a slightly higher degree of severity
than crashes at other locations. Mohamedshah et. al (2001) indicate an
increasing trend in fatal crashes at signalized intersections between 1992 and
1996, increasing by some 18 percent from 1,888 in 1992. Retting et. al (1998)
reported that annually some 260,000 red-light-running (RLR) crashes occurred in
the US of which 750 crashes are fatal.
The above numbers indicate that crashes at signalized intersections and, in
particular, RLR crashes are worthy of attention and counter-measures ought to
be sought to alleviate this problem. One of the counter-measures generally
considered is police enforcement and in the case of red-light running, automatic
enforcement with the aid of red-light cameras.
The generally held view on the effectiveness of enforcement is that a
combination of factors should be looked at. The deterrence effect is the
combined result of enforcement and punishment as manifested in the subjective
risk of apprehension. In risk of apprehension, it is certainty that produces the
greatest effect. Certainty is a question of type of enforcement and intensity. In
punishment, the most important factor seems to be swiftness (Shinar and
McKnight, 1984).
The following paper will bring together literature that has been published on the
subject of RLR crashes. It will briefly deal with driver behaviour at signalized
intersections as manifested in violation rates, i.e. the number of drivers passing
against the red light and with the characteristics of the intersections associated
with RLR, but most of the attention will be focused on the crash data at signalized
intersections in the context of the installation of red-light cameras.
2. BRIEF OVERVIEW OF HISTORIC DEVELOPMENT
The use of automatic cameras at signalized intersections started in Europe in the
early l970s, in Australia on a wide scale in the 1980’s and in the US in the early
© Association for European Transport 2002
1990’s. Levinson (1989) reports on the use of red-light cameras in Israel as early
as 1969. The cameras are generally activated a fraction of a second up to one
second after the onset of the red signal. A vehicle crossing on red is captured
twice, with a one-second interval between photographs to document its progress.
Video cameras, which have been introduced recently, work on a different
principle and record a sequence of frames of the violating vehicle as it passes
through the intersection.
New York city was the major jurisdiction in the US that started applying RLCs on
a large scale. Initially 18 intersections were equipped with cameras. Other
jurisdictions followed-Howard County, MD and San Francisco, CA in 1996,
Oxnard, CA in 1997 and others somewhat later. To date, about 70 communities
in the United States have implemented RLC enforcement (IIHS, 2001).
Automatic camera enforcement is attractive to many police forces. There is the
potential for a police enforcement agent to be present at a spot for 24 hours
every day, it could be unobtrusive (if that is the preferred tactic) and it produces a
record of evidence that can not be easily disputed. Furthermore, it can generate
a large number of citations thus influencing drivers in an efficient and costeffective manner. On the other hand, this type of enforcement created new
issues and challenges- legal, technical and operational. The simple chain of
evidence in a manual citation has the observing police officer identify an
offending driver and hand her or him a citation, in person. With automatic
cameras, there is no eyewitness and the identity of the offending driver cannot be
ascertained at the time of the offence. The evidence has to be fool proof and the
identity of the offender must be somehow extracted from the photographic
record. Processing large number of film (or video) records, guarantying tamperproof handling, maintaining equipment, all present special challenges. In all
cases, the legal system has to be adapted to accept this type of enforcement.
Great Britain is one of the countries with widespread use of automatic
enforcement of speeding offences and of red-light running. About 34 percent of
all speeding tickets are issued by the use of speed cameras and 22 percent of all
junction related offences are from RLCs. Out of 313,000 tickets issued in 1997 in
England and Wales, 88 percent were for speeding and 12 percent for running red
lights (Zaidel, 2000)
2.1 Automated systems
The current RLC systems use wet film, digital film and video to record the
violation. Although sometimes called automatic enforcement, these systems are
by no means automatic. The loading and unloading of the film, the transfer of the
films for processing and parts of the ensuing processing and ticketing systems
are done by hand. A truly automatic system would enable the process to run from
the stage of recording the violation till the issuing of the ticket without human
intervention, keeping in mind, that safeguards would have to be built into such a
© Association for European Transport 2002
system for a human operator to intervene in all cases where the slightest doubt
arises. Some applications have been developed and tested that approach such
an automated system. A Dutch company developed a digital system for speed
measurement along a stretch of road that incorporates video cameras, a licenseplate reader enabling automatic vehicle identification of violators, transmission of
the pictures to a central processing location and automatic issuing of tickets.
After an initial trial period, the system has yet to be put into wider operational use.
3. DRIVER VIOLATIONS AT TRAFFIC SIGNALS AND BEHAVIOURAL
ASPECTS
A large number of studies have dealt with the aspect of drivers traveling through
the red-light at signalized intersections (Retting et. al, 1999a; Retting et. al,
1999b; Chin, 1989; Baguley, 1988; Greene, 2000). Some studies were mostly
concerned with the number and frequency of red-light violations while other
studies have also dealt with the mechanism of red-light violations, i.e. the time
interval since the onset of the red till the violation, the vehicle manoeuvre,
characteristics of the drivers, etc. Some of these aspects will be summarized and
described in the following sections. Baguley (1988) was one of the first to study
the red light running phenomenon in detail. Drivers approaching a traffic signal
are in some cases caught in what is termed a dilemma-zone. The driver is said to
be in the dilemma-zone if the amber period (a standard three seconds in the U.K)
is insufficient for him either to stop comfortably, or to clear the stop-line before
the red-phase begins. In this situation the driver has the possibility to either brake
hard with a possibility of coming to a halt after the stop-line, or to continue and
cross the stop-line after the onset of the red. A partial, engineering solution is
provided for these cases by providing an all-red phase to the signal, which delays
conflicting traffic from entering the intersection. Studying the characteristics of
drivers entering the intersection after the onset of the red light Baguley divided
such drivers into three groups: drivers who were caught in the dilemma zone,
drivers who should have been able to stop comfortably, but deliberately
continued into the red and those who appeared completely unaware that they
continued through a red signal. Various traffic engineering measures can be
selected to improve safety in the case of drivers from the first group. Such
measures include green phase extensions for drivers approaching at high
speeds, all-red clearance intervals and measures to reduce speeds on traffic
signal approaches. For drivers of the other two groups, red-light camera
enforcement offers an effective solution.
3.1 Studies of violations at signalized intersections
This section discusses the number and proportion of drivers that violate the red
light according to the various studies that dealt with the subject. Table 1
summarises the results from ten various studies.
© Association for European Transport 2002
Table 1 Summary table with results of studies with red-light violations at
signalized intersections
Reference
Country
Description of
study
Retting et.
al (1999a)
USA
5 camera
sites
2 noncamera sites
2 comparison
sites
Retting et.
al (1999b)
Chin
(1989)
Woolley
and Taylor
(1998)
USA
Singapor
e
Australia
Number of
violations
Before
After
192
334
Great
Britain
Percent
change
Comments
-44
Rateviolations
4
per 10
vehicles
Violationsentering
0.4
seconds or
more after
red onset
Rateviolations
4
per 10
vehicles
Violationsentering
0.4
seconds or
more after
red onset
Rateviolations
per cycle
188
135
37.8
25.0
-34
51
53
7.6
7.7
+5
9 camera
sites
3 noncamera sites
2 comparison
sites
719
98
455
48
12.9
16.0
7.7
8.0
-40
-50
22
19
7.0
6.7
-4
23 camera
approaches
20 noncamera
approaches
14
comparison
sites
12 sites
N/a
N/a
0.344
0.201
-42
0.326
0.239
-27
0.283
0.331
+17
Range 0.180.84
Range 0.390.83 at
pedestrian
crossing
0.33, 0.39
ranked 3 and 4
out of 12
Range5.7 – 33.4
percent of free
flowing vehicles
N/a
Rateviolations
per 100
passing
vehicles
N/a
Free
flowing
vehicles is
2.3 – 3.2 %
of total
major road
flow
Total- 298,049
vehicles were
counted
2 sites with
cameras
Baguley
(1988)
Rate of
violations
Before
After
20.4
36.3
7 rural sites
3830 free
flowing vehicles
670 red-light
runners
© Association for European Transport 2002
Kent et. al
(1995)
Australia
3 RLC in
Melbourne
and Geelong
Metropolitan
areas
38000 vehicle
movements
observed
123
encroachments
0.32 percent
encroachments
N/a
Greene
(2000)
Australia
15 sites
133,238
vehicles
observed
522 red-light
incidents
N/a
Lawson
(1991)
Great
Britain
14 sites in
Birmingham
N/a
2.4 incidents
per hour
3.9 incidents
per 1000
vehicles
1 incident per
25 cycles
1% of vehicles
crossed against
the red. At one
site- 6%
Oei et. al
(1997)
The
Netherla
nds
4 sites in
Amsterdam
3000
1308
3.4%
1.5%
-56
Thompson
et. al
(1989)
Great
Britain
Nottingham
Site 1
Site 2
60
149
44
168
1.4%
3.1%
1.1%
3.5%
-22
+13
© Association for European Transport 2002
N/a
93% of
encroachm
ents
occurred
during the
all-red
phase
Rateincidents
as
proportion
of all
passing
vehicles
Percent of
vehicles in
the
decisionarea that
had
opportunity
to violate
Rate –
percent of
entering
vehicles
Violations
range
1.6%-8.2%
before to
0.5%-3.4%
after
Violations
as percent
of vehicles
arriving
and
stopping on
red
The various authors have adopted different rates to describe the violation
patterns. Retting et. al (1999a, 1999b) define the rate of violation as the number
of violations per 10,000 entering vehicles. Chin (1989) uses the number of
violations per signal cycle, whereas most other studies, including Woolley and
Taylor (1998), Green (2000), Kent et. al (1995), Lawson (1991) and Oei et. al
(1997) use violations per hundred passing vehicles. Baguley measures violations
as a proportion of free-flowing vehicles at a distance up to 150 metres from the
stop line, not crossing during amber. The proportions of violations vary largely
between studies and countries, but a number of generalizations can be made.
The studies from the US, Great Britain and the Netherlands report violation rates
of between 0.5 to 7 percent of entering vehicles. The studies from Australia
generally report lower violation rates of below one percent. This is presumably
related to driving and enforcement practices in the various countries. Australia
has a long tradition of red-light camera enforcement, which has been
accompanied by high-profile publicity.
Those studies that measured violation rates before and after the installation of
RLC invariably found large reductions in violation rates at camera sites or on
camera approaches, in the order of 40 to 50 percent (Except an early study at
two sites in Nottingham - Thompson et. al, 1989). Rocchi and Hemsing (1997)
reviewing a number of studies most of which are also covered in the present
study, report on reductions in violations ranging between 0 and 75 percent. With
publicity the reductions in violations range from 21 to 75 percent. The Nottingham
study with a zero reduction in violations shows that it is important to advertise the
introduction of a camera program. Large reductions were also found at sites near
camera locations or near camera approaches, in the order of 30 to 50 percent.
This occurred at a time when violation rates at sites not related to the camera
sites, i.e. control sites, generally went up (Retting et al, 1999a and Chin) or
decreased slightly (Retting et al, 1999b). Taking changes in violation rates as an
indication of possible changes in crash rates, this seems to indicate that studies
where crash rates at camera approaches are compared with those at other
approaches of the same intersection, or with rates at nearby intersections are
seriously underestimating the RLC effect on both violation rates and on crashes.
The reason is that drivers are adjusting their behaviour in a more general way
and not only on the camera approaches, a “halo” effect.
One other aspect that should be considered is that a red light violation is defined
differently from country to country. In many US jurisdictions, violations are
defined as a passing of the stop line 0.4 seconds or more after the onset of the
red light. An additional requirement is that the vehicle travels at a speed of 15
miles or more, so that slow moving right turning vehicles (the right turn on redafter stop manoeuvre, where permitted) are not captured. In Maryland a violation
is recorded from 0.1 second after red onset. In South Australia (Earl and Coxon,
1996), a violation starts only 1 second after the onset of red. A shorter delay after
red onset will invariably increase the number of violations.
© Association for European Transport 2002
4. CRASH STUDIES
4.1 Aggregate studies of intersection crashes and crashes related to redlight running
Intersection crashes form a large part of the crash population and a significant
proportion of such crashes can be associated with red light running at signalized
intersections. Table 2 shows that intersection and intersection-related crashes in
the US make up 45 percent of all police reportable crashes in 1999, 49 percent of
all injury producing crashes and 23 percent of the fatal crashes. Crashes at
signalized intersections make up 20, 23 and 7 percent respectively.
Table 2. Data on crashes in the US by type of location for the year 1999 (NHTSA,
2000)
All levels of severity
number
percentage
All crashes 6,279,000
100
Intersection 2,806,000
45
crashes
Signalised 1,278,000
20
intersection
crashes
Injury crashes
Fatal crashes
number
percentage number percentage
2,054,000
100
37,043
100
1,015,000
49
8,514
23
476,000
23
2,691
7
Table 3 summarises the results from the studies conducted in the US, Great
Britain and Australia, which have looked at details of crashes at signalized
intersections.
The studies conducted in the US show a range of 5 to 9 percent of crashes at
signalized intersections associated with RLR. Within the US the various results
are very consistent. The Australian study indicates 15 to 19 percent of crashes
can be RLR related. The study from Great Britain identifies 25 to 36 percent of
crashes as RLR related. Some of these differences, which are very large, might
be associated with behavioural differences between countries and differences in
setting inter-green times at signalised intersections. Other differences in police
coding procedures might also have contributed to these differences.
4.2 Before-after evaluations of red-light camera installation
Considering the effect of camera installation on the number of red-light violations,
the reasonable assumption being that, in many cases, it is the red-light violation
that precedes a crash. However, it cannot be said that red-light violations in most
cases lead to a crash, especially those that occur during the first two seconds of
the red signal, part of which may be part of an all-red phase. It is therefore not
enough to study the changes in rates and patterns of violations and one has to
look also at changes in crashes that occur after the installation of cameras.
© Association for European Transport 2002
Table 3. Studies with details of crashes at signalized intersections
Source
Year
Country
Retting et
al
2000
USA
Retting et
al
1999
c
USA
Lawson
Greene
Mohamedshah,
Chen,
Council
1991
2000
2001
Great
Britain
Australia
USA
Number of
intersections
Total - 122
51experimental
56 comparison
Large nationwide data
bases, five
years data
1992-1996
29 intersections
In Birmingham
with RLR
problems
5 years
168 signalised
intersections in
Birmingham,
one year’s data
1989
5 years data
1985-1990 in
Birmingham
Years 19941998
Victoria,
Western
Australia,
Queensland
1756 signalised
urban
intersections
© Association for European Transport 2002
Total number
of crashes
1,044experimental
Before
941experimental
After
1323
comparison
Before
1298
comparison
After
6,833,669
policereported
crashes
Number of RLR
crashes
N/a
Percentage
3753 RLR fatal
crashes
257,849 RLR
police-reported
crashes (of which
208,355 are injury
producing)
276 accidents
N/a
7 fatal
68 serious
injury
343 slight
injury
418 total
2018
accidents
N/a
N/a
508 RLR accidents
25.2
percent
Crashes at
signalized
intersections
Relevant crashes
to RLR - 2688
crashes
1479
756
accidents
with injuries
53,247
crashes
8 percent
reduction
at
experiment
al sites
after signal
re-timing
(not
significant)
5 percent
36.5
percent
19 percent
15 percent
1589
21 percent
4709 crashes
8.8 percent
4.2.1 Description of studies with information on crashes and their results at
intersections with cameras
Overall, 12 studies and reviews were identified, from the USA (2 studies),
Australia (6), Great Britain (2), Singapore (1) and Norway (1 - review), that had
quantitative results on the number of crashes at signalized intersections before
and after the installation of red-light cameras. The main results of these studies
and reviews are summarized in table 4.
The changes in the numbers of crashes shown in table 4 are the numbers quoted
by the authors, which are the result of the methods they used in their studies. As
will be shown in the joint analysis, in some cases different results are obtained by
using a different statistical technique.
Looking at the results it can be concluded that most of the studies reported crash
reductions as a result of the installation of red-light cameras at signalized
intersections. Some of the studies pointed to the fact that the reduction in
crashes was not found to be statistically significant. Some of the studies noted a
reduction in right-angle crashes and an increase in rear-end crashes
(Andreassen, 1995; South et. al, 1988; Hillier et. al, 1993; Ng et. al, 1997). But
other studies, notably the studies by Office of Auditor General (1996) and Mann
et. al (1994) did not find such increases. Other studies did not disaggregate the
crash results by type and provide results of overall changes. Some studies
differentiated between crashes with injuries and all reportable crashes, including
property-damage-only accidents.
The range of reported crash reductions is wide and varies from a reduction of 7
percent in all crashes (Retting and Kyrychenko, 2001) to 18 percent (Hooke et.al,
1996) and 41 percent in property damage crashes in Queensland (1995); from a
6.7 percent reduction in crashes with injuries (South et.al, 1988), to 16-60
percent in Queensland (1995) and 29 percent in (Retting and Kyrychenko, 2001).
Generally, reductions in right-angle crashes were larger and in some cases the
number of rear-end crashes increased. The more severe crashes were reduced
more than the non-injury crashes. Rocchi and Hemsing (1997) report on 12
studies from Australia, the United States and the United Kingdom. They found
reductions ranging from 10 to 50 percent in the number of angle collisions.
4.2.2 Joint analysis
To quantify the results of the various studies in a more meaningful way a joint
analysis was conducted for all those studies that provided the required details.
The joint analysis weighted the results obtained from the different studies using
Odds ratio evaluations. Each study is weighted according to the relative number
of crashes it contributes to the total. To calculate the Odds-ratio, the number of
crashes in the before and after periods is needed, for both the
© Association for European Transport 2002
Table 4. Summary and results from 12 studies with details of crashes at sites
with cameras
Number of
intersection
s with
cameras
11
Average
crash
reduction
Incl. in
metaanalysis
7%-all
crashes,
29%-injury
crashes
Yes
46
10.4%-all
casualties,
6.7%-all
crashes
with injury
32%-right
angle
crashes
50%-in
right angle
crashes,
25-60%
increase in
rear-end
crashes
Changes in
numbers of
crashes
were not
found
statistically
significant
Changes in
number of
crashes
were not
found
statistically
significant
40% in
right-angle
crashes,
little
change in
rear-end
crashes
Yes
Referen
ce
Year
Town, state
country
Details of study
Retting
and
Kyryche
nko
2001
Oxnard,
USA
South
et. al
1988
Victoria,
Australia
Number of crashes
and injury crashes at
camera sites and
non-camera sites in
treatment community
and comparison
communities
Number of crashes
with injuries, by type
of crash at camera
and control sites
Hillier,
et. al
1993
NSW,
Australia
Number of crashes
and crashes with
injuries by crash type
at camera and control
sites
20
Andreas
sen
1995
Victoria,
Australia
Number of crashes,
incl. with injury, by
type of crash at
camera approaches
and non-camera
approaches
41
Mann et.
al
1994
South
Australia
Number of crashes
and crashes with
injury at camera and
control sites
8
Office of
Auditor
general
1996
Western
Australia
Number of crashes
per intersection, by
type at camera and
non-camera
intersections
44
© Association for European Transport 2002
Yes
Yes
Yes
No
Review of studies in
various US
communities, incl.
Oxnard
Rates of crashes with
injuries at sites with
red-light cameras
before and after
camera installation
Literature review and
meta-analysis of
three Small
Scandinavian studies
Varying
numbers
Varying
results
No
113
18% in
crash rates
per
intersection
No
N/a
No
Queenslan
d
Australia
Crashes and crashes
with injuries at
signalized
intersections with and
without cameras
79
1990
Great
Britain
Crashes with injuries
before and after
camera installation by
type of crash
5
1997
Singapore
Rates of crashes with
injuries before and
after camera
installation, at
camera sites and at
comparison sites
All camera
sites-125
Beforeafter-42
sites
45%-fatal
crashes
12%-injury
crashes
9%property
damage
crashes
Over 50%
in fatal
crashes
16-60% in
crashes
with
injuries
41% in
property
damage
crashes
10%-all
crashes
68%-“fail to
conform”
crashes
16%-in
crashes
with
casualties
at 125 sites
19% at 42
sites
Hasson
2000
USA
Hooke,
et. al
1996
Great
Britain
Elvik et.
al
1997
Various
countries
Queensl
and
1995
County
Surveyo
rs
Ng et. al
© Association for European Transport 2002
Yes
No
Yes
treatment and valid comparison (control) sites. Of the thirteen studies described
above, only seven studies provided detailed results, which enabled to include
them in the joint analysis of the effect of camera installation on the crash
frequencies at signalized intersections. These were the studies by Retting and
Kyrychenko (2001), South et al (1988), Hillier et. al (1993), Andreassen (1995),
Mann et. al (1994), Queensland (1995) and Ng et. al (1997). The first study
relates to the USA, the last one is from Singapore and all the others relate to
results from Australian studies.
Results (Table 5) were attained first for studies that included both crashes with
casualties and crashes with property damage above a certain monetary value,
these groups combined are termed reportable crashes. A further calculation was
performed on those studies that provided separate results for crashes with
injuries. The injury crashes were further split up into right-angle crashes, which
are those that might most likely be affected by the camera installation and rearend crashes which, according to some of the reports might be adversely affected.
Only some of the seven studies provided further details about the types of
crashes involved. These were the studies by South et. al (1988), Hillier et. al
(1993) and Mann et.al (1994). Right-angle crashes include collisions between
vehicles on adjacent approaches and other right-angle crashes. Rear-end
collisions include crashes between vehicles on the same approach and other
rear-end crashes.
Table 5. Results from the joint analysis with crash reductions and statistical
significance
Type of
analysis
Total crashes
Injury crashes
Right-angle
injury
Rear-end
injury
Weighted odds- Change in
ratio
crashes
0.796
20% reduction
0.730
27% reduction
0.836
16% reduction
Statistical
significance
yes
yes
yes(just)
1.096
not
significant
10% increase
No. of
studies
5
6
3
3
The definition of sites included in each study differ somewhat. Retting and
Kyrychenko (2001) include signalized intersections in the treatment group and
use two types of comparison sites. One group is signalized intersections in
comparison communities, whereas the other type uses non-signalized
intersections in the treatment community. The study by South et. al (1988) uses
slightly differing before and after periods, defined in terms of intersection-years,
i.e. the number of intersections times the number of years in each period.
Because the differences were less than 3 percent this effect was ignored. The
study by Andreassen (1995) used intersection approaches on which a camera
© Association for European Transport 2002
was installed as the treatment sites and other approaches at the same
intersections as comparison sites. It has by now been well documented that
when cameras are installed, the number of red-light violations decreases at both
camera sites and at sites nearby, either other approaches of the same
intersection or nearby intersections. The real effect of cameras is thus
underestimated. The study by Mann et. al (1994) looked at eight sites at which
cameras were installed and at another five sites (termed RLC modified) at which
also various engineering improvements were made. The joint analysis included
only the eight RLC sites without modifications. In the study from Queensland
(Queensland, 1995) the cameras were installed over a period of five years 19911995. These years were excluded from the analysis making the years 1986-1990
the before period and the years 1996-2000 the after period.
Table 5 shows that the studies reviewed demonstrate an overall reduction of 20
percent in crashes as the result of the installation of red-light cameras. The
overall reduction in the number of injury crashes is estimated at 27 percent. A
reduction of 16% is noted in the number of right-angle crashes and a notsignificant increase of 10% is observed in the number of rear-end-crashes.
Looking at the contribution of each study to the weighted overall results, it was
noted that the study from Queensland, being much larger than the other studies,
contributed most to the overall weights and also had the largest reduction in
crashes. The results were therefore calculated a second time without the
Queensland data. Results are presented in Table 6. The Queensland study did
not provide details of the types of crashes at camera and non-camera locations
Table 6. Results from the joint analysis without the Queensland study
Type of
analysis
Total crashes
Injury crashes
Weighted
odds-ratio
0.926
0.832
Change in
crashes
7% reduction
17% reduction
Statistical
significance
yes
yes
Table 6 shows that the overall results remain the same, although the effect is
somewhat reduced.
The overall conclusion of the combined analysis of the effectiveness of the
camera installation in the seven studies included is that the installation of the
cameras proved effective in all studies reviewed. The overall effectiveness can
be estimated as a 20 percent reduction in crashes of all severities, a 27 percent
reduction in crashes with injuries and a 16 percent reduction in right-angle
crashes. The increase in rear-end crashes of 10 percent, although not statistically
significant was noted in four of the seven studies.
© Association for European Transport 2002
5. DISCUSSION AND CONCLUSIONS
The ultimate goal of police enforcement is to achieve normative changes in the
public's behaviour to come into closer agreement with the laws and regulations.
Only in this manner is it likely that enforcement can be effective, in the long run,
within reasonable bounds of manpower and resources.
Literature dealing with the effectiveness of conventional enforcement seems to
indicate that such normative changes are unlikely to be achieved with the levels
and methods of enforcement presently used in most countries (Makinen and Oei,
1992; ETSC, 1999). Whereas some changes, sometimes drastic, can be
achieved locally in road user behaviour, these changes are generally limited in
time and distance, and do not produce lasting impacts, neither on behaviour nor
on the number of road accidents associated with these types of behaviour. The
explanation seems to lie in the fact that normative changes are not achieved
because the changes in behaviour are not internalized. It is believed that a
considerable increase in the risk of apprehension is required in order to achieve
the desired effect.
Such an effect might be achieved with the aid of a variety of methods of
automatic enforcement. This type of enforcement could be applied on a much
wider scale. The technologies have been developed to make this kind of
enforcement possible and feasible. In many countries, the laws and regulations
have been adapted to make automatic enforcement possible, and public opinion,
although not always very favorable, seems to agree with a gradual introduction of
this type of enforcement.
Various traffic engineering measures can be selected to improve safety in the
case of drivers who enter the intersection during the first 1-2 seconds of red.
Such measures include green phase extensions for drivers approaching at high
speeds, all-red clearance intervals and measures to reduce speeds on traffic
signal approaches. For drivers who enter the intersection deliberately, red-light
camera enforcement offers an effective solution.
As has been demonstrated in this study, red light cameras are highly effective in
reducing the number of drivers entering an intersection on red. Reductions in the
order of 40- 50 percent were found in those studies reviewed that observed
violation rates before and after the installation of red light cameras.
Not unexpectedly, cameras were also effective in reducing crashes. Overall
reductions of 20 percent in all crashes (based on five studies) and of 27 percent
in crashes with injuries (based on six studies) are the best estimates on the basis
of those studies that provided detailed information on the number of crashes.
Other studies that provided information only on changes in crash rates show a
wider range of crash reductions but no study indicated an increase in crashes.
© Association for European Transport 2002
One of the criticisms raised in the context of red-light enforcement programs
concerns the outsourcing of the process to private companies. This criticism is
mostly relevant to US practices and not to other countries where outsourcing is
not common. Although the outsourcing is done for matters of efficiency and is
always conducted under strict instructions and supervision of the responsible
jurisdiction, some of the opposition could be alleviated by activating the camera
system only after one second of red and not, as is now customary in most US
jurisdictions, 0.3-0.4 seconds after red onset. It was shown in various studies that
the safety problem created by drivers entering the intersection during the first 1-2
seconds of red can be treated with various traffic engineering solutions.
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© Association for European Transport 2002