1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
SAFETY IMPACT OF HIGH FRICTION SURFACE TREATMENT INSTALLATIONS
IN PENNSYLVANIA
Kimberley Musey
Graduate Research Assistant
Department of Civil and Environmental Engineering
Villanova University
800 Lancaster Avenue
Villanova, PA 19085
Email: [email protected]
Seri Park, Ph.D., PTP *
Assistant Professor
Department of Civil and Environmental Engineering
Villanova Center for the Advancement of Sustainability in Engineering (VCASE)
Villanova University
800 Lancaster Avenue
Villanova, PA 19085
Email: [email protected]
Monica Kares
Undergraduate Research Assistant
Department of Civil and Environmental Engineering
Villanova University
800 Lancaster Avenue
Villanova, PA 19085
Email: [email protected]
Date of Submission: November 15, 2016
Paper Submitted to the 95th Annual Meeting of the Transportation Research Board
January 8-12, 2017, Washington, D.C.
Number of words: 5,607 Total number of words: 7,357 (Max: 7500 words)
Number of tables: (4x 250 = 1000) Number of figures: (3 x 250 = 750)
* Corresponding Author
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
0
ABSTRACT
Each year, thousands of drivers in the United States are involved in motor vehicle crashes. In order
to address this issue, transportation professionals have continued to investigate countermeasures
to improve roadway safety including high friction surface treatments (HFSTs). This treatment
maximizes the existing infrastructure, and provides exceptional skid resistance in spot locations
where friction demand is critical, such as intersection approaches or horizontal curves.
Since the early 2000s, there has been an increase in state HFST installation projects. This
research seeks to evaluate the performance of HFST installation projects in the state of
Pennsylvania from both a safety and economic perspective. Using project construction and crash
data provided by the Pennsylvania Department of Transportation (PennDOT), it reviews how
effective the installations were in reducing both crash rates and crash severity through a beforeafter and benefit-cost study of over 70 sites. The results of these two investigations show that
Pennsylvania received the greatest reduction in crash number and severity as well as the greatest
return on investment for intersections on horizontal curves that are located in an urban environment.
The results, along with further statistical analysis, will be used in future study to develop
crash modification factors to quantify the expected crash reduction that can be expected at a
particular location by installing HFSTs, with the ultimate goal of helping DOTs maximize return
on investment and to better anticipate the safety benefits of HFSTs when programming projects.
Keywords: High Friction Surface Treatment, Crash Severity, Benefit-Cost Ratio, Return on
Investment
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
1
INTRODUCTION AND BACKGROUND
According to the National Highway Traffic Safety Administration (NHTSA), a total of 35,092
people died in motor vehicle crashes on the U.S. highway system in the year 2015 (1). According
to the Pennsylvania State Transportation Innovation Council, Pennsylvania experienced nearly
200 fatalities and 500 major injuries each year involving crashes on slippery or wet pavement over
a recent period of five years (2). From statistics such as these, it is evident that transportation
professionals need to investigate cost efficient and sustainable methods of improving roadway
safety.
Since the early 2000s, there has been an increase in state HFST installations projects as a
safety countermeasure. According to the FHWA, noteworthy practices have been seen in a number
of states including Kentucky, South Carolina, California, Florida, New York, and others. Now that
HFSTs are continuing to be implemented on such a wide scale, it is important, to evaluate how
they are performing, and determine the extent of their effectiveness in reducing crash rates and
crash severity. In addition, studies should be conducted to evaluate the long-term benefits versus
the project costs.
This paper seeks to review the performance of several HFST installations from a safety
and economic perspective through an analysis of projects in the State of Pennsylvania. It includes
a before-after analysis and benefit-cost study of over 74 sites. The results along with further
statistical analysis were also used to develop a number of crash modification factors (e.g. for an
urban, rural, intersection, segment, curve, or tangent facility) to calculate the expected crash
reduction when deciding whether or not to proceed with a HFST project.
This study uses data provided by the Pennsylvania Department of Transportation
(PennDOT). The completed research from the state of Pennsylvania will serve as a proof of
concept, but can be expanded in the future to include other states. The goal of this study is use
results to enable DOTs to better anticipate the safety benefits of HFSTs prior to implementing new
projects. The findings can also be used by DOTs to determine the top locations to invest in HFST
projects for the maximum safety impact and best return on investment. The findings would greatly
benefit transportation agencies when programming projects and carefully investing government
funds to meet traffic safety goals.
RESEARCH OBJECTIVES
The objectives of this research are to:
 Conduct a comprehensive review and analysis of crash data to further explore the impact
of HFST installation on crash rates and crash severity for projects in Pennsylvania;
 Perform before-and after analyses of the crash data;
 Conduct a benefit-cost study of HFTS installations; and
 Establish a basis for future research that includes the development of a crash modification
factor (CMF) of pavement friction factor along with other site specific features (e.g. degree
of horizontal curvatures, rural vs urban environments, and other roadway features.
This paper is organized into major sections that include: a background and reviews of HFST
installation projects; detailed crash data description and analysis methodology; resulting dataset
findings; and the future direction of this research.
LITERATURE REVIEW
Pavement Friction
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
2
When dealing with roadways, friction factor is the amount of resistive force between a vehicle
tires and the road. The degree of roadway friction is generally quantified using what is known as
a skid number. Pavement friction plays a very important role in driver safety. Overall, the less
friction that is available, the less a driver can control his vehicle. Friction becomes a problem
particularly under wet, icy, or slippery conditions. Even small amounts of water on the road surface
can reduce friction by 20% to 30% (3). Therefore, friction plays a critical role in pavement and
geometric roadway design.
High Friction Surface Treatments
Horizontal curves, steep grades, and intersection approaches are all locations where drivers tend
to brake excessively. As a result, the roadway tends to lose its friction more quickly than other
locations. This reduction in pavement friction causes vehicles to skid, depart from the lane on
curves, or rear-end leading vehicles when approaching an intersection. HFST are pavement
treatment systems that can be applied at these spot locations to provide drivers with exceptional
skid resistance and for a much longer period of time than traditional paving (2). The greater
pavement friction causes the loss of microtexture friction due to the wet weather to be less critical
(3).
Calcined bauxite is the recommended aggregate for use in HFST applications due to their
high resistance to polishing (4). Other materials that have also been evaluated for this purpose
include flint, granite, and slags, which are all commercially available. The binder materials can
include Bitumen-extended epoxy resins, epoxy resin, polyester-resin, polyurethane-resin, or
acrylic-resin. The installation process can be done with either manual or machine automated
mixing (5).
HFST have a moderate cost compared to other alternatives when considering the life cycle
of the pavement. Construction is also relatively short, meaning that construction is likely to have
a minimal impact on the general public. It can therefore be a sustainable and cost-effective option
to preventing roadway crashes and fatalities. Continuing to incorporate additional pavement
friction in design may be a key element in ensuring roadway safety (6).
Case Studies
HFST arrived in Pennsylvania in the year 2007. The roadway chosen for this pilot program was a
horizontal curve in which vehicles regularly slid on the pavement into either guiderail, or even
more dangerously, into opposing traffic. After many attempts at a solution, HST was decided to
be applied. The district reported that the results were immediate, with “wet-pavement-related
crashes at the spot drop from 20 in the 10 years prior to the treatment to zero in the seven years
since it has been installed” (2). These positive results lead to the deployment of several similar
projects, which continue to experience similar success in reducing crashes.
Pennsylvania, however, is not the only state to experience the benefits of HFSTs. Since the
early 2000s, there has been an increase in installation projects across the United States. In fact, .
As of July 2015, 80% of states have utilized HFSTs in at least one location (7). In the state of
Kentucky, some rural areas are characterized by very mountainous terrain, which presents a
challenge to drivers. 32 sites were chosen for the installation of high friction surfaces from the year
2009 through 2011. The treatments comprised of a compound comprising a two-part, highly
modified epoxy resin binder and a specially graded, high-friction bauxite aggregate. According to
FHWA’s Everyday Counts initiative, a preliminary evaluation of 26 projects shows a 69%
reduction in crashes (4). One particular project focused on Oldham County Bridge Hill. This
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
3
particular area had experienced 59 crashes from August 1, 2007 through August 1, 2009, resulting
in 23 injuries and 1 fatality. HFST was installed for a total cost of $66,500. As of April 2013, only
5 crashes were reported. These results among others in this state, led the state to develop an official
HFST program that selects sites based on the Empirical Bayes methodology (8).
The state of South Carolina also experienced positive results from HFST installation. A
one-mile section of US 25 was traversed a rural and mountainous terrain, contained sharp
horizontal and vertical curves, and experienced high operating speeds. When HFST was installed
in 2008, wet crashes were reduced by 68 percent and total crashes by 56 percent. Other locations
in South Carolina also experienced benefits. One study that considered seven HFST installations,
reported that there was an 81 percent reduction in wet crashes and 71 percent reduction in total
crashes (9).
In addition to looking purely at before and after data, some studies have also been
conducted that look into the benefit-cost ratios associated with HFST projects. A recent before and
after study from the SCDOT performed a similar analysis for a series of horizontal curves. The
study revealed benefit-cost ratios of about 24 to 1. In contract, the State of Kentucky placed HFST
on 26 curves, and saw values from 6.2 to 1.9 at those locations (10).
The State of Florida also conducted a study identified 23 HFST sites in Florida. These were
each analyzed based upon its bidding records, roadway geometry, and crash history. The cost of
installing each project was determined by the average HFST unit cost, and was scaled by the size
of the application. The “savings” were calculated based on the average cost per crash severity from
the Department of Transportation’s KABCO scale. “On average, HFST applications on tight
curves reduced the total crash rate by 32% and the wet weather crash rate by 75%. The average
BC ratio on tight curve sections was between 18 and 26. Wide curve and tangents sections had few
accidents initially, and HFST had negligible impact” (11).
HFST Life Expectancy
Just like pavement performance, HFST wear is dependent on many things such as initial
construction quality, friction demand, and traffic volume as well as the severity of the climate and
the weight and number of heavy truck axle (5). As a result, life expectancy of is difficult to
generalize since it will vary with type of roadway, geometry, traffic volume and type. International
data indicates that if it is correctly applied, the expected service life is at least 7-12 years. Some
data from the United States indicate a service life of over 15 years when applied to bridge deck.
For approximately 15,000 vehicles per day, vendors have reported that the HFST lasted anywhere
from 5-8 years. For a greater amount of 50,000 vehicles per day, the HFST lasted up to 5 years
(5).
Some states have been experiencing issues with the durability of HFSTs. In Kansas for
example, four locations were chosen on both existing asphalt and concrete pavement to evaluate
the long term effectiveness and durability of the high friction surface materials. In general, total
surfaces are performing poorly, with one of the lower trafficked surfaces failing in less than three
years. The surfaces on concrete are peeling off and skid resistance numbers are dropping. One way
to improve the durability is through appropriate site preparation and a review of the application
specifications (12). Sand blasting the surface to remove contaminants and filling any existing
cracks is crucial in order to get a strong bond between the asphalt and the HFST that will not
separate and create spalls and patching with use over time (13).
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
4
Risk Analysis
Traditionally, engineers have used a nominal approach to safety, and often left to use good
engineering judgment to make design choices. However, recent risk assessment methodologies,
such as the one proposed by Ray and Carrigan (14) demonstrate that a more quantitative approach
for measuring the risk associated with design alternatives can help to identify where the greatest
safety benefit can be realized, which is directly in line with the goals of this research.
STUDY LOCATION AND DATA COLLECTION
This research utilized crash data provided by the Pennsylvania Department of Transportation.
(PennDOT). The crash database includes crash data from PennDOT Districts 1, 2, 4, 5, 6, 8 and
12. A variety of sites were included from rural and urban facilities, intersections and segments,
horizontal curves and tangents. The number of lanes ranged from two to six, and speed limits
ranged from 15 mile-per-hour (mph) to over 55 mph. Some sites included features like rumble
stripes, medians. The data file used in this research contained a total of 3064 crashes from the years
2003 through 2016.
Each crash data entry recorded by PennDOT included detailed information on the crashes,
including the county, state route, segment and offset where the crashes took place, the date and
time of the crash, lighting, roadway surface conditions, weather, crash severity, environmental
roadway factors, vehicle events, and driver actions. This information was crucial to analyze how
each of these features correlated to the occurrence of crash events.
In addition to the crash database, PennDOT also provided a database of its HFST projects
throughout the state, both planned and completed. As of March 2016, this included 140 locations
where HFST projects were completed, and 60 that were planned or in construction. These projects
are in nearly all counties in the state. In this database, each project site has a Multi-modal Project
Management System (MPMS) number, district, county, state route, segment, offset, targeted crash
type, actual/anticipated completion date, funding source, and amount of funding.
METHODOLOGY
This paper seeks to review the performance of HFSTs from a safety and economic perspective
through an analysis of HFST installation projects in the State of Pennsylvania. Only projects with
a completion date of 2015 or earlier were included in this study in order to ensure at least one year
of crash data after HFST installation necessary to compare to the crash history prior to the
installation. In addition, only locations where geometric features can be found were included. This
reduced the dataset to approximately 74 locations from the original 140 locations, and are shown
in Figure 1 below.
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
5
FIGURE 1 Map of Study Site Locations
The first step of was the crash data compiling and database construction process. This
involved collecting the crash records provided by PennDOT, followed by a review to the ensure
accuracy of the data transfer. Then, a second database was constructed for the details regarding
HFST projects throughout the state. This process involved the use of PennDOT’s multimodal
project management system (MPMS) query, Engineering and Construction Management System
(ECMS), Internet Traffic Monitoring System (iTMS) and google earth to obtain roadway features
for each site. This information includes lane number, shoulder information, clearance zones,
median type or other barriers, segment length, the presence of rumble strips, speed limit, AADT,
rural/urban, functional classification, whether it was an intersection or segment, tangent or curve,
and curve degree if applicable. During this step, each project site was assigned a unique site
identification number.
After this data was also filtered and reviewed, steps 2 and 3 of this research involved the
before and after analysis. This began by going through all each of the 3,064 crashes individually,
and correlating them to its respective site identification number based on the county, state route,
segment, and offset. The site ID and the HFST installation date from the second database to
determine whether the crash occurred before or after the HFST was installed, and then to calculate
the number of years between these dates. From here, two before-and-after analyses were performed,
one limiting the crash data to the same number of years before and after the HFST installation, and
one analysis where the data is averaged based on the years of data available before and after
installation. This is performed for each project site when the data is available.
Step 4 was a benefit-cost analysis. This analysis used the results of the two before-after
analyses along with project cost information from ECMS and the MPMS Query. Costs were
obtained by dividing total project cost proportionally to the site segment lengths within each
project to determine the cost of each site. The benefits were determined based upon the reduction
in crashes by severity levels.
Musey et al
1
2
3
6
The last step focuses on the development of Crash Modification Factors for the effect of
HFST. A summary of this methodology is presented in Figure 2. It should be noted that step 5 is
still under investigation and hence, this paper presents findings through step 4.
PennDOT
Crash Data
STEP 1: Database Building
STEP 2: Same Period Before-After Study
PennDOT ECMS,
iTMS, and MPMS
Query Construction
Data
STEP 3: Averaged Before-After Study
STEP 4: Economic Analysis
STEP 5: Crash Modification Factor
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
FIGURE 2 Research Process Flow Chart
DATA ANALYSIS AND RESULTS
Before-After Analysis
As defined in the methodology portion of this report, the before-after analysis was divided into
two comparisons. One analysis involved limiting crashes per site to include only those with the
same before period of time before and after the HFST installation. The second comparison
considered the average number of crashes per year before and after HFST installation. Both of
these were to ensure that the comparison of crashes before and after was fair. This section will
describe the results of each investigation.
Total Data Analysis
The top portion of Table 1 shows the results of the simple before-after analysis. For this
investigation crash data was limited to crashes within the same period before and after the HFST
installation. For more recent projects, data was often limited by the available crash data after the
project was completed. For example, if HFST was installed on January 1st 2013, a crash database
ending in June 2016 would mean 3.5 years of “after” crash data. Therefore, the “before” crash data
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
7
was limited to only include crashes 3.5 years prior to the January 2013 install. For the 74 sites, the
periods used varied from less than a year to four years.
TABLE 1 Before-After Analysis
Before
After
Crash Reduction
Simple Before-After Analysis
6
0
-6
Fatal
9
4
-5
Major Injury
29
8
-21
Moderate Injury
98
9
-89
Minor Injury
265
37
-228
PDO
72
6
-66
Unknown Injury
479
64
-415
Total
Average Crashes Per Year
3
0
-3
Fatal
6
3
-3
Major Injury
22
5
-17
Moderate Injury
70
8
-62
Minor Injury
171
41
-130
PDO
44
6
-38
Unknown Injury
315
62
-253
Total
% Reduction
100.0
55.6
72.4
90.8
86.0
91.7
86.6
100.0
48.9
79.3
89.0
76.0
86.6
80.3
As a result of the simple before-after analysis, the total percent reduction in crashes across
all severity levels was 86.6%. The installation of HFST was able to eliminate fatalities by 100%
at all of the 74 sites. The severity level with the least percent crash reduction was major injury,
however, installing HFST still reduced crashes here by 72.4%. Overall, the total data showed that
HFST improved roadway safety by reducing both the number and the highest severity of crashes.
The bottom portion of Table 1 shows the before-after analysis for the averaged data. As
mentioned previously, the number of crashes before and after are divided by the total years of
before and after crash data respectively. Therefore, the results are represented in average crashes
per year. The total percent reduction in crashes across all severity levels was 80.3%. Once again,
the installation of HFST was able to eliminate fatalities by 100% at all of the 74 sites. The severity
level with the least percent crash reduction was major injury, however, installing HFST still
reduced crashes here by 48.9%. Overall, the total data in both analyses showed that HFST
improved roadway safety by reducing both the number and the highest severity of crashes.
Individual Site Analysis
After the analysis of the data as a whole, the sites were analyzed on an individual basis. First
examined was in the framework of the simple before-after analysis. Of the 74 total sites, 35 were
able to eliminate total crashes among all severity levels by 100%. 11 sites actually saw an increase
in total crashes; however, the maximum increase was only by 2 crashes, and the severity of crashes
after installation tended to be much lower with the majority being PDO crashes and none of the
crashes being fatal. Locations with the highest crash reductions were also investigated to identify
any similarities between the geometric and operational features of these sites. From this
examination, it is of note that 60% were in urban areas, 71% were intersection related crashes, and
Musey et al
8
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
89% were associated with a horizontal curve, with low and medium curvature sites experiencing
the greatest reduction.
After the simple before-after analysis was the individual site investigation for the averaged
data. Of the 74 total sites, 46 were able to reduce total crashes among all severity levels by 100%.
6 sites actually saw an increase in one of their crash categories; however, the maximum increase
was only by 4.77 average crashes per year, and the severity of crashes after installation were much
lower with the majority being PDO crashes, a few minor injuries, and none of the crashes being
fatal. Locations with the highest crash reductions were also investigated to identify any similarities
between the geometric and operational features of these sites. From this examination, it is of note
that 67% were in urban areas, 74% were intersection related crashes, and 87% were associated
with a degree of horizontal curvature, with low curvature sites experiencing the greatest reduction.
20
21
22
23
24
25
26
27
28
FIGURE 3 Examples of Low, Medium, and High Curvature Roadway Sites
29
Impact of Curvature
The next area that the dataset examined was the impact of horizontal curve degree on crashes in
locations where HSFT were considered. Examples of high, medium, and low curvature from the
PennDOT installation sites can be found in Figure 3 below. These categories were defined based
on the angle, θ, between the two legs of the curve along with Google imagery. Low curvature was
had an angle θ from about 150-180°, medium curvature from 120-150°, and high curvature from
0-120°.
Table 2 shows the simple before-after analysis when the sites were broken down by
curvature. For this dataset, the greatest reduction in crashes, however, was seen by medium
curvature roadways, followed by high curvature. However, it is noteworthy that these values are
relatively close. Also, it is worth noting is crash severity. All of the fatalities prior to HFST
occurred on low curvature roadways, and the installation was able to reduce these fatalities to zero
during the analysis period. Therefore, HFST appear to be a good solution for all degrees of
curvature.
Musey et al
TABLE 2 Simple Before-After Analysis by Curvature
High
Curvature
Med
Curvature
Low
Curvature
1
9
Crash Severity
Before
After
Reduction in
Crashes
% Reduction
Death
Major Injury
Moderate Injury
Minor Injury
PDO
Unknown Injury
Total
Death
Major Injury
Moderate Injury
Minor Injury
PDO
Unknown Injury
Total
Death
Major Injury
Moderate Injury
Minor Injury
PDO
Unknown Injury
Total
6
4
17
44
91
20
0
0
6
0
16
0
6
4
11
44
75
20
100%
100%
65%
100%
82%
100%
182
22
160
88%
0
3
7
15
50
16
91
0
1
5
29
87
16
138
0
0
1
0
5
0
6
0
0
1
0
13
0
14
0
3
6
15
45
16
85
0
1
4
29
74
16
124
-100%
86%
100%
90%
100%
93%
-100%
80%
100%
85%
100%
90%
2
3
4
5
6
7
8
9
10
Table 3 shows the same curvature investigation for the averaged data. The same guidelines
were used in defining curvature categories as in the previous simple before-after analysis. The
greatest reduction in crashes, was seen by medium curvature roadways, followed by high
curvature. Similar to the previous investigation, however, when considering crash severity, all
fatalities occurred on low curvature roadways (an average of 2 per year). Therefore, the ability of
HFST to eliminate fatalities until the end of the data collection period shows that such projects
may be a good solution on all curvature roadways.
Musey et al
TABLE 3 Average Crashes Per Year Before-After Analysis by Curvature
Reduction in
Crash Severity
Before
After
Crashes
2
0
2
Death
3
0
3
Major Injury
8
3
6
Moderate Injury
25
0
25
Minor Injury
51
19
32
PDO
9
0
9
Unknown Injury
98
21
77
Total
0
0
0
Death
1
0
1
Major Injury
5
0
5
Moderate Injury
15
0
15
Minor Injury
41
8
33
PDO
12
0
12
Unknown Injury
75
9
66
Total
0
0
0
Death
1
0
1
Major Injury
5
2
4
Moderate Injury
18
0
18
Minor Injury
47
9
38
PDO
8
0
8
Unknown Injury
79
11
69
Total
High
Curvature
Med
Curvature
Low
Curvature
1
10
% Reduction
100%
100%
68%
100%
64%
100%
78%
100%
100%
95%
100%
79%
100%
88%
100%
100%
69%
100%
81%
100%
87%
2
3
BENEFIT-COST RATIO
4
5
6
7
8
While a before-after analysis suggests practitioners the types of roadway facilities that experienced
the greatest percent reduction in crashes, a benefit-cost analysis will indicate which types of
locations will provide the greatest return on investment (ROI). A benefit cost ratio summarizes the
overall value for money of a project or proposal. As shown in equation 1, the ratio is calculated by
dividing the expected benefit of proceeding with a project by the costs.
9
10
11
12
13
14
15
16
17
18
19
𝐵⁄𝐶 𝑅𝑎𝑡𝑖𝑜 =
Total Benefit from Crash Reduction
Total Installation Costs
(𝐸𝑞𝑢𝑎𝑡𝑖𝑜𝑛 1)
Having a B/C ratio greater than 1.0, indicates that the benefit outweighs the cost, and often
provides evidence that the project is recommended to proceed. Based on this formula, the greater
B/C Ratio, the better the argument that the project was successful and fulfilled its objective. This
is particularly important because limited project budgets, so transportation professionals must
ensure that resources are used in the most efficient way possible.
For this analysis, the cost of the project (per site) was determined based on the material and
construction costs to install the HFST. This information was obtained on the PennDOT ECMS
website. In general, HFSTs are considered to be an economical approach to roadway safety. When
compared with transportation related construction projects with budgets in the million-dollar
Musey et al
11
1
2
3
4
5
6
7
range, HFSTs cost between tens or hundreds of thousand dollars. For this dataset, the prices of
installation per site ranged from about $95,000 to $180,000.
The benefit of installing HFST was measured based on the lives and injuries saved, which
was measured in the reduction in crashes by severity. The average cost associated with each injury
level can be seen in Table 4 below, and are based on data provided by PennDOT from the years
2010 to 2014. These were multiplied by the reduction in crashes for each corresponding severity
level, to calculate the total benefit that was derived from the project.
8
TABLE 4 Costs Per Crash Severity
Crash Severity
Fatal
Major Injury
Moderate Injury
Minor Injury
PDO
Unknown
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
$
$
$
$
$
$
Average Cost
6,245,689.80
1,365,629.20
91,285.40
7,245.00
2,898.00
7,245.00
For the B/C analysis, the averaged data was used in order to define the average benefit cost
ratio per year of installing HFSTs. The benefit-cost ratio for the combined cost and benefit of all
projects was 3.5. When the sites were examined individually, the median B/C ratio was 0.9 and
the mean was 7.4. The minimum B/C ratio observed was -29.1, and the maximum was at a value
of 137.5. 38 (51%) of the 74 sites where HFST was installed resulted in a B/C ratio greater than
1.0. All of these results indicate that while individual projects may vary quite significantly, the
overall value of deploying multiple HFST projects may provide desirable ROI costs.
The greatest returns on investment for this dataset were experienced by 2-lane roadways
(which represented the majority of the project sites) with the following ranks and features:
1. Site #16 – SR 0147, Rural, minor arterial, intersection, tangent
2. Site #17 – SR 1001, Rural, minor collector, segment, horizontal curve
3. Site #3 – SR 0329, Urban, minor arterial, segment, horizontal curve
4. Site #12 – SR 1009, Urban, Urban collector, intersection, horizontal curve
5. Site #13 – SR 2024, Urban, minor arterial, intersection, horizontal curve
6. Site #14 – SR 2017, Urban, minor arterial, intersection, horizontal curve
The least return on investment for this dataset also occurred on 2-lane roadways with the following
ranks and features:
1. Site #75 – SR 3033, Rural, minor collector, segment, horizontal curve
2. Site #67 – SR 0352, Urban, minor arterial, segment, horizontal curve
3. Site #34 – SR 4030, Rural, major collector, intersection, horizontal curve
4. Site #2 – SR 0100, Rural, principal arterial, segment, horizontal curve
5. Site #33 – SR 2024, Rural, local road, intersection, horizontal curve
6. Site # 97 – SR 2005, Rural, major collector, intersection, horizontal curve
In terms of ROI, 4 of the top 6 sites were in an urban environment, while 5 of the bottom 6
were in a rural setting. In addition, 4 of the top 6 sites were impacted by an intersection, while 4
of the bottom 6 sites were associated with a roadway segment. Based on these two lists, it may be
determined that PennDOT received the best return on investment in urban environments and at
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
12
intersections. Therefore, when taking cost into consideration, these results are in agreement with
the two previous before-after analyses.
Although horizontal curves were represented in both the top and bottom ranked B/C ratios
for the dataset, this may simply be due to the fact that curves represent the vast majority of HFST
projects. Therefore, in line with the benefit cost analyses, it can be deduced that in addition to an
urban intersection, horizontal curves also serve as critical locations for HFST.
CONCLUSIONS AND NEXT STEPS
Conclusions
This research sought to perform a comprehensive review and analysis of PennDOT crash data to
determine the efficiency of HFST projects throughout the state of Pennsylvania. It evaluated their
ability to reduce not only crash occurrences, but also crash severity. This was performed by means
of two before-and after analyses, one in which the same crash history period was used before and
after the HFST installation. The second analysis averaged that data and therefore results were
reported in average crashes per year. The two before-after analyses were conducted on a total of
74 sites. For this particular dataset, the HFST was able to reduce the number of crashes by at least
75% for each degree of curvature and each crash severity. Most importantly, fatalities at all sites
were reduced by 100%. Sites with the greatest reduction in total crashes were urban environments,
intersections, and horizontal curves.
The results of the benefit cost analysis showed very similar results in the selection of
roadway facilities. However, comparing the individual sites indicated that while overall return on
investment is high when deploying a large number of HFST projects throughout the state, the
return on investment for individual projects may not show the same promising results.
Overall this paper shows that HFST installations throughout the state of Pennsylvania have
been effective in their goal of reducing both crash rates and severity. For this dataset, PennDOT
received the greatest results at intersections involving horizontal curvature that are located in urban
environments. Therefore, these may potentially be the types of facilities that departments of
transportation could target first in order to most efficiently improve roadway safety.
Future Research
The next phase of this research will involve regression modeling in order to develop crash
modification factor that could be used to help predict the safety impact of installing HFST at a site
in the future. The study will also be expanded to include a complete crash dataset, and any other
HFST project sites that have been completed since output of this report. Afterwards, future
research may include crash data and studies in other states and an analysis to determine the trend
of crashes after HFST and determine if crash reductions persist or if a learning curve is present.
ACKNOWLEDGEMENTS
The authors would like to acknowledge the PennDOT for providing the data which was used as a
part of this research. The contents of this paper do not necessarily reflect the official views or
policies of the State of Pennsylvania.
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
13
REFERENCES
1. National Highway Traffic Safety Administration. 2015 Motor Vehicle Crashes: Overview.
August 2016. US Department of Transportation. DOT HS 812 318.
https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/812318http://wwwnrd.nhtsa.dot.gov/Pubs/812160.pdf. Accessed July 24, 2015.October 31, 2016.
2. State Transportation Innovation Council, PennDOT. High Friction Surface Treatment.
FHWA. http://www.dot.state.pa.us/public/pdf/STCTAC/STIC/HFS_FACT_SHEET.PDF.
Accessed July 29, 2016.
3. Albin, R., V. Brinkly, J. Cheung, et al. Low-Cost Treatments for Horizontal Curve Safety
2016. Federal Highway Administration. FHWA-SA-15-084. January 2016.
http://safety.fhwa.dot.gov/roadway_dept/horicurves/fhwasa15084/ch5.cfm#ch5a. Accessed
July 29, 2016.
4. Julian, F. High Friction Surface Treatments. 2013. Everyday Counts 2: NACE Conference.
http://www.countyengineers.org/events/annualconf/Documents/2013%20Presentations/Hi%2
0Fric%20Treatments%20Julian.pdf. Accessed May 2015.
5. Cheung, Joseph. Federal Highway Administration. High Friction Surface Treatments.
USDOT. https://www.fhwa.dot.gov/everydaycounts/edctwo/2012/pdfs/fhwa-cai-14019_faqs_hfst_mar2014_508.pdf. Accessed June2015.
6. Pulugurtha, S.S., P.R. Kusam, K.J. Patel. Assessing the Role of Pavement Macrotexture in
Preventing Crashes on Highways. Traffic Injury Prevention, Vol. 11, Issue 1, 2010, pp. 96103.
7. Federal Highway Administration. High Friction Surface Treatments (HFST). September 6,
2016. United States Department of Transportation.
http://safety.fhwa.dot.gov/roadway_dept/pavement_friction/high_friction/. Accessed October
28, 2016
8. Federal Highway Administration. Case Study: Kentucky Transportation Cabinet’s High
Friction Surface Treatment and Field Installation Program. FHWA-SA-15-038.
http://safety.fhwa.dot.gov/roadway_dept/pavement_friction/case_studies_noteworthy_prac/k
ytc/ky_hfst_15_038.pdf. Accessed October 23, 2016.
9. Federal Highway Administration. South Carolina Case Study: A Cost-Effective and TimeSensitive Safety Solution. FHWA-SA-15-056.
http://safety.fhwa.dot.gov/roadway_dept/pavement_friction/case_studies_noteworthy_prac/s
c/sc.pdf. Accessed October 23, 2016.
10. Federal Highway Administration. Frequently Asked Questions about High Friction Surface
Treatments (HFST). https://www.fhwa.dot.gov/innovation/everydaycounts/edc-2/pdfs/fhwacai-14-019_faqs_hfst_mar2014_508.pdf. Accessed October 23, 2016.
11. Wilson, B. T., Brimley, B. K., Mills, J., et al. Benefit–Cost Analysis of Florida High-Friction
Surface Treatments. In Transportation Research Record: Journal of the Transportation
Research Board, Volume 2550. DOI: 10.3141/2550-08. Transportation Research Board of
the National Academies, Washington, D.C.
12. Meggers, D. Evaluation of High Friction Surface Locations in Kansas. Paper No. 15-0377
submitted for the 94th Annual Meeting Transportation Research Board, Kansas Department
of Transportation, Topeka, KS, 2015, pp. 1.
Musey et al
1
2
3
4
5
6
7
8
9
10
11
12
13
14
13. Hall, J. W., Smith, K.L., Titus-Glover, L. Guide-for-Pavement-Friction. In National
Cooperative Highway Research Program. Project 01-43, Transportation Research Board of
the National Academies, Washington, D.C.,
2009.http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_w108.pdf
14. Ray, M. and C. Carrigan. Use of Risk Analysis to Minimize Adverse Consequences in
Nonstandard Designs. In Transportation Research Record: Journal of the Transportation
Research Board, Volume 2521. DOI: 10.3141/2521-12. Transportation Research Board of
the National Academies, Washington, D.C.
15. Harkey, D. L., R. Srinivasan, J. Back, et al. Accident Modification Factors for Traffic
Engineering and ITS Improvements. In Transportation Research Record: National
Cooperative Highway Research Program, Report 617, Transportation Research Board of the
National Academies, Washington, D.C., 2008, pp. 22-24.