Accident Patterns in Road Construction Work Zones

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46
Accident Patterns in Road Construction Work Zones
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
ABSTRACT: Traffic safety in road construction zones has always been a major concern for engineering practitioners,
departments of transportation, law enforcement professionals, researchers and many others. Due to the deteriorated
condition of road and underground infrastructure facilities in the United States, the number of rehabilitation projects
and their associated traffic accidents have increased over the past few years. To perform the needed road and underground
utility rehabilitation activities in safer environments, researchers need to understand the causes behind these accidents.
Although many researchers have been exploring the safety of many construction activities, research pertaining to road
construction projects is lacking and insufficient. Despite the fact that few research efforts have been made to fill in this
reported gap, many important collision factors have not yet been explored. This paper augments earlier safety research
work by analyzing 11 years’ worth of data and presenting a wide range of primary factors that contribute to traffic
accidents in road construction zones. The paper also presents the impact of many factors, such as environmental and
road conditions on the type and severity of collisions. The findings presented in this paper will not only contribute to
the reduction of construction zone related traffic accidents by avoiding their causes, but it will also assist contractors
and transportation authorities in better planning and scheduling their projects in a manner that positively contributes
to the safety of served communities. This will be achieved by presenting factors that highly influence the decision on the
start dates and duration of projects such as, day(s) of the week and month(s) of the year that are mostly associated with
higher rates of traffic collisions.
INTRODUCTION
Accident Patterns in Road Construction Work Zones
Tariq Shehab, Ph.D
California State University, Long Beach | shehab@csulb.edu
Leah Phu, M.Sc.
California State University, Long Beach | Leah.phu@gmail.com
Keywords: Safety, Roads, Construction, Accidents,
Heavy Civil.
Construction projects are listed among the most
risky work environments in many countries. In
the United States, the Business Insider ranked
the construction industry among the 15 most
dangerous US jobs (Lubin and Lincoln 2011).
In 2012, 3.7% of full time construction workers
had non-fatal occupational injuries, and at least
3 American workers may fail to return home by
the end of every working day due to fatalities
on construction sites, which is about 17% of fatal
accidents across all industries (Bureau of Labor
Statistics 2013, Chi and Han 2013, Solis-Carlos
and Arcudia-Abad 2013).
On the international level, it was documented that
about four annual fatal construction accidents per
100,000 workers may take place in the United
Kingdom. In Singapore, Chile and Mexico, the
construction accidents per 100,000 workers are
nine, 18 and 21, respectively (Solis-Carlos and
Arcudia-Abad, 2013 and Haslam et al. 2005).
Falkner et al. (2012) documented that while the
number of fatal accidents in Finland, Netherlands,
Switzerland, Ireland, Sweden, Norway, Japan,
France and Belgium is less than ten workers per
100,000 workers, the number of fatal accidents in
Tariq Shehab
is an associate professor of construction engineering and management. His area of expertise includes heavy civil
construction.
Leah Phu
is a research assistant in the area of construction engineering and management. Her area of expertise includes traffic
management and accidents in the construction industry.

Accident Patterns in Road Construction Work Zones 47
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
LITERATURE REVIEW
Thailand, Indonesia, South Africa and Russia is
between 10 and 40 workers per 100,000 workers.
While so many researchers have been exploring
the safety environments in many types of
construction activities, limited research has
addressed the highway construction sector (Kim
et al. 2013 and Arditi et al. 2007). The following
information presents the research that addresses
road construction projects.
Kemper et al. (1984), focused on the impact of
narrow lanes for traffic control on construction
sites. The researchers concluded that narrow lanes
contributed significantly to rates of construction
zone related traffic accidents. They reported that
when the nine foot-wide lane was introduced
to the public, the traffic accident rate increased
from 1.68 accidents per million vehicle-miles to
2.63 accidents per million vehicle-miles. They
also reported that when an 11 foot-wide lane was
used, the traffic accident rates were less than the
rate associated with a nine-foot lane.
Bryden et al. (1998) analyzed three years’ worth of
data on New York Department of Transportation
highway construction projects, and reported that
33% of all work zone traffic accidents were related
to pavement bumps and joints, drainage features,
excavation materials and construction vehicles.
Their analysis revealed that 20% of all construction
zone traffic accidents involved construction
vehicles, equipment and/or pedestrian workers.
Bryden and Andrew (1999) covered a five-year
study period and reported that traffic accidents
accounted for 20% and 40% of serious injuries and
fatal accidents on construction sites, respectively.
Although the study identified three types of traffic
accidents (i.e. vehicles that collide with other
vehicles, fixed objects and pedestrians), it did not
address the collisions’ contributing factors.
Mohan and Gautam (2002) addressed the cost of
highway work zone injuries over three years. They
reported that while 30% of the reported accidents
involved construction workers, 70% involved
motorists. The types of motorist accidents reported
in this study were overturning, rear-end collision,
small-hit-object, large-hit-object and side impact.
The direct overall cost associated with these types
of accidents ranged from $5.74 to $6.75 billion.
Qi et al. (2005) reported, based on a seven year study
period, that construction work zones had more rear-
end accidents compared to non-construction work
zones. They also reported that rear-end accidents
in which alcohol, night conditions, and pedestrians
were involved were more severe. Furthermore,
rear-end accidents that took place before the work
area approach taper were much more severe
compared to other work zone locations (e.g. after
and within work area zones.
Bai and Li (2006) focused on fatal accidents only
and reported that male drivers caused about 75%
of fatal work zone accidents in Kansas. These
accidents were mainly attributed to inattentive
driving and misjudgment. Drivers aged of 35 to
44 were associated with the highest percentage
of fatal accidents. While drivers younger than 55
caused most nighttime accidents, drivers between
35 and 44, and older than 65, caused the most
daytime accidents.
Arditi et al. (2007) studied the impact of
daytime and nighttime on accidents in highway
construction zones. The study focused on fatal
accidents only, and was based on a five-year study
period. The researchers found that nighttime
highway construction projects were five times
more hazardous than daytime projects. They
found that weather parameters had very limited
effect on this conclusion.
Li and Bai (2008) compared characteristics
between fatal and injurious accidents in highway
construction zones during a period of five years.
The researchers focused on head-on and rear-end
collisions. They reported that head-on and rear-end
were the most common types for fatal accidents
and injuries, respectively. The researchers also
reported that while ignored traffic control, alcohol,

48
Accident Patterns in Road Construction Work Zones
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
DATA COLLECTION
and speeding caused a large proportion of fatal
accidents (about 60%), tailgating and inattention
had a very high contribution to injuries (about
70%). Unfavorable light conditions caused more
fatal accidents than injuries.
Kim et al. (2013) studied the factors that
contributed to non-traffic accidents on highway
construction projects. They classified highway
construction work into six groups: drainage,
tunnels, installations, earthmoving operations,
paving activities and structures. The researchers
reported that types of accidents vary between
these six groups of projects. Although the
researchers did a very good job in showing the
significant differences between accidents that take
places on six types of construction activities, they
limited these differences to time of accidents and
provided very few causes of accidents (e.g. fall
and struck by).
Farmer et al. (2013) reported that 120 death cases,
at least, were attributed to road construction
activities in Texas, Georgia, California and Florida
in 2010. Snyder and Associates (2013) reported
that the US daily injury and death rates due to
road construction activities were about two and
100 persons, respectively. Furthermore, 85% of
killed people are motorists. The National Work
Zone Safety Information (2013) reported about
600 national work zones traffic fatality cases in
2010, about 50% of which were in Texas, Georgia.
Florida, California, Illinois, Pennsylvania and
Oklahoma. It further reported that about 2% of
traffic crash fatalities took place in construction
work zones. The National Highway Traffic Safety
Administration (2014) reported that total national
yearly property damage was about $900 billion.
Although the aforementioned studies present
excellent and valuable safety research regarding
road construction projects, Kim et al. (2013) and
Arditi et al. (2007) agreed on the need to expand
and the research to explore additional safety issues
related to this class of projects. Furthermore, Kim
et al. (2013) reported that research pertaining
to road construction projects was lacking and
insufficient.
This research is presented to fulfill the reported
need to understand traffic collisions in road
construction projects, which accounts for the
majority of accidents in this category of the
construction industry, and to identify their
contributing causes. It fills in the gap in safety
research work by focusing on traffic accidents
in construction zones only. It augments earlier
research presented in the literature and overcomes
the existing limitations, such as not addressing
a wide variety of primary collision contributing
factors, focusing on limited types of collisions and
addressing fatal accidents only. This study went
beyond previous ones by investigating additional
important and influential factors such as traffic
volumes, roadway classifications, property
damages and human errors during the daytimes
and nighttime. It ameliorates the knowledge
of traffic accidents in road construction work
zones by highlighting a wide range of issues (e.g.
contributing factors and roadway classifications)
that should be addressed by the team of road
project participants, including contractors, to
minimize traffic accidents in this class of projects.
It uses information collected from traffic accident
reports that were prepared during a period of 11
years in Buena Park, California.
Data for construction zone related collisions that
happened from January 1, 1999 to December 31,
2009 were downloaded from the City Traffic of
Buena Park Collision Database. To perform this
task, Crossroads software was used. Buena Park
is home to about 80,000 people in the northwestern
part of Orange County, CA, where two major
freeways intersect: Interstates 5 (I-5) and State
Route 91(SR-91). Buena Park is classified as an
entertainment zone (E-Zone), where attractions
such as Knott’s Berry Farm, Medieval Times
Dinner and Tournament, Ripley’s “Believe It or
Not!” Museum, Knott’s Soak City and the Pirates
Dinner Adventure are located.

Accident Patterns in Road Construction Work Zones 49
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
RESULTS
To perform this study, the authors focused on
accidents that took place within construction work
zones, which are defined as sections of highway
where construction, repair, or maintenance was
being performed. A construction work zone could
be divided into four sections: 1) advanced warning
section; 2) transition section; 3) activity section
and 4) termination section (U.S. Department of
Transportation 2009).
In the advanced warning section, single or multiple
signs are used and may be up to 0.5 miles long.
The transitional section is where a reduction in
road width is required. This reduction is achieved
using tapers, which vary in length, depending on
speed limits (U.S. Department of Transportation
2009). The activity section is where work takes
place, and could be stationary or moving. The
termination section consists of a downstream taper
that may extend up to 100 feet beyond the activity
section. A more detailed description regarding the
characteristics of construction zone sections, such
as speed limits and dimensions, were presented in
the U.S. Department of Transportation (2009).
During the 11 year analysis period, 9,426 traffic
accidents were reported. A closer look at the
traffic collision reports reveals that the following
ten pieces of information are documented in
each report: 1) time of day; 2) day of the week;
3) month and year; 4) lighting condition (e.g.
daylight or dark-no street lights); 5) type of
collision (e.g. head-on or rear end); 6) primary
collision factor (e.g. unsafe speed or unsafe lane
change); 7) objects involved with collision (e.g.
pedestrians or other motor vehicles); severity
(e.g. injury or fatality); 8) weather condition (e.g.
raining or cloudy); 9) roadway surface condition
(e.g. wet or dry) and 10) traffic control devices
(e.g. not present or not functioning). A sample
collision report can be found on the Accreditation
Commission for Traffic Accident Reconstruction
(ACTAR) website (ACTAR 2013). The following
information presents the number and percentages
of traffic accidents associated with each of the
aforementioned ten pieces of information.
The following information reflects the magnitude
of traffic accidents related to construction work
activities and provide more information about
their contributing factors.
Construction Zone Related Collisions Versus
Total Collisions
To compare the total number of traffic accidents to
those related to construction activities, all accidents
reported between 1999 and 2009 were analyzed.
This analysis revealed a total of 9,426 accidents,
out of which, 204 happened in construction zones.
The distribution of these 204 accidents over the 11
year study period is shown in Figure 1. As shown
Figure 1: Number of Collisions Vs. year

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Accident Patterns in Road Construction Work Zones
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
in Figure 1, the two leading years with the most
work zone related accidents were 1999 and 2008.
While the reduction in the number of accidents that
took place from 2000 to 2007 could be attributed to
improvements in safety procedures, the increase
in the number of accidents that took place in 2008
was mainly attributed to about 25% increase in
number of public work construction projects,
including those related to I-5 improvement plans.
Table 1 shows that construction zone related traffic
collisions account for about 2% of all reported traffic
collisions that occurred in the City of Buena Park
within the 11 year time period. In view of the overall
national statistics reported by Farmer et al. (2013),
Snyder & Associates (2013), and National Work Zone
Safety Information, along with the insistent need to
minimize death and injury cases in road construction
work zones, 2% it is too high to be ignored.
Table 1: Construction Zone Related Collisions Versus Total Collisions
Type of Accident
Number of Accidents
Percentage (%)
Construction zone
related
204
2.0
Non-Constuction
Related
9222
98.0
Extent of Injuries
The extent of injuries in construction work zones
included four options listed on accident reports: 1)
injury; 2) fatal; 3) property damage only and 4) none.
Table 2 presents that property damage and injuries were
equally reported to be 49%, each. While one case was
reported as fatal (about 0.5%) only, three cases were
classified as none within the 11 years of data. It should
be noted that a damage description to private property is
noted on traffic collision reports, and the investigating
officer is required to notify the owner. However, private
property damages are settled financially between the
responsible party and the private owner, and thus the
city would not have any record of private property
damage expenses.
Table 2: Severity of Accident in Construction Work Zones
Severity
Percentage (%)
Injury
49.0
Fatal
0.5
Property Damage Only
49.0
None
1.5
Time Information
Figure 2 shows that most of the work zone traffic
collisions occurred during the daytime period of 7:00
AM to 5:00 PM As depicted in Figure 2, there are four
major spikes at 2:00 AM, 7:00 AM, 1:00 PM and 5:00
PM, respectively. To understand the causes of these
spikes, the researchers had a second look at the accident
reports. Although this further investigation revealed
that the obvious increase in the number of work zone
accidents at 2:00 AM was mainly due to driving under
the influence (DUI), no obvious reasons were found
to explain the spikes at 7:00 AM, 1:00 PM and 5:00
PM, except that there was an increase in traffic volume
during rush hours. It should be noted that positive DUI
laboratory results take up to 30 days to be reported and
documented in the collision reports.
Figure 2: Time of Day Vs. Number of Collisions

Accident Patterns in Road Construction Work Zones 51
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
To validate this theory, a study of traffic volume was
needed throughout the city of Buena Park. Due to the
huge volume of data, the researchers considered a
random sample of one week of data associated with
Valley View Street. This street is one of the major
arterials in the city of Buena Park and is associated
with the highest average daily traffic (ADT) counts
(i.e. 45,000). (City of Buena Park 2013). It should be
noted that no information related to the number of
construction projects that took place on this street and/
or their associated number of traffic collisions were
available to the researchers. Analysis of the traffic
volume on this street is depicted in Figures 3 and 4.
While Figure 3 focuses on weekdays, Figure 4 focuses
on weekends. As shown in Figure 3, traffic peaks
during weekdays are around 8:00 AM and near 6:00
PM with the majority of traffic accumulating between
7:00 AM and 9:00 PM Figure 4 shows that the highest
traffic volumes are between 11:00 AM and 5:00 PM,
which partially explains the spike at 1:00 PM in Figure
2. It should be noted that Figures 3 and 4 indicate that
traffic volumes during weekdays and weekends are
about the same (i.e. 16,000 vehicles per day). This
could be attributed to the entertainment nature of
Buena Park. It should be also noted that although this
validation approach provided reasonable justification,
other validation approaches that use construction work
zone data need to be attempted.
Figure 3: Weekdays Example Traffic Data
Figure 4: Weekends Example Traffic Data
Lighting Information
Figure 5 reveals that the majority of work zone related traffic
collisions (i.e. 75%) occurred in the daytime where daylight
was the main source of lighting. The nighttime period had a
relatively low crash rate (i.e. 22%). Because these statistics
may indicate that motorists may have a tendency to drive more
cautiously at night around work zone traffic control zones,
further comparisons between traffic volumes during day and
night times were performed using information depicted in
Figures 3 and 4, respectively. This comparison revealed that
nighttime traffic volume is about 7% of that associated with
daytime (about 1,000 vph versus 15,000 vph). This comparison
may suggest that accidents during nighttime should be about
7% of those occurring during daytime. Since information
depicted in Figure 5 shows that collisions that occur during
nighttime are about 30% of those occurring during daytime
(22% versus 75%), this indicates that lighting conditions
positively contribute to crash rates. It should be noted that
more discussion about the impact of lighting condition on the
number and type of collisions is presented in the following
section titled Primary Collision Factors.
Figure 5: Lighting Condition vs. Number of Collisions

52
Accident Patterns in Road Construction Work Zones
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
Day of the Week Information
While Figures 3 and 4 indicate that traffic volumes during
weekdays and weekends are about the same (16,000 vehicles
per day), Figure 6 shows that the number of collisions during
weekends is significantly lower than weekdays. This is
partially attributed to the impact of work fatigue on drivers.
Furthermore, Figure 6 shows that work zone traffic collisions
increase gradually on Mondays, and then decline after
Tuesday. By comparing Figures 3, 4 and 6, it is noticed that
although Tuesday is associated with the highest number of
accidents, it is not associated with the highest traffic volume.
Upon further efforts to explain the results shown in Figure 5,
the city of Buena Park minimizes lane closures and prohibits
construction work on weekends, thus explaining the low
number of work zone traffic collisions. Furthermore, upon
interviewing the Certified Public Infrastructure Inspector
regarding possible explanations for the high occurrence on
Tuesdays, public work inspectors tend to start construction
projects on Mondays and do not begin lane closures until
9 am that day. Since initial lane closures do not begin
until Mondays at 9 a.m., most people are at work, and
accordingly, do not run into the traffic control for the first
time until the next morning, this may lead to a combination
of motorist confusion and frustration during their commutes
on Tuesdays.
Figure 6: Days of the Week vs. Number of Collisions
Figure 7: Months of the Year vs. Number of Collisions

Accident Patterns in Road Construction Work Zones 53
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
Months of the Year Information
Figure 7 shows that in the busy Entertainment city of Buena
Park, most of the work zone related traffic collisions tend to
accrue during the summer months. About 34% of the crashes
were reported in slow-construction seasons including
November, December, January, February, and March. It can
be speculated that summer months tend to attract drivers that
are not familiar with the area, especially since the city of
Buena Park attracts thousands of tourists every year to its
Entertainment Zone. Tourists, who are usually new visitors
to the area and are unfamiliar with the street network, may
find themselves confused when traffic control and detours
are present.
Collision Type
Figure 8 shows that the most frequently encountered
types of collisions are rear-end collisions (34%),
broadside/right-angle (27%), sideswipe collisions
(20%) and hit objects (9%). The dominance of rear-end
collisions indicates that relatively high speed and/or
following too closely were contributing factors. The
large number of right-angle collisions also suggests
a high incidence of right-of-way violations or non-
compliance for traffic signals and/or stop signs.
Sideswipe collisions may be mostly associated with
unsafe lane changes.
Figure 8: Collision Types
Primary Collision Factors
Primary collision factors could be generally attributed
to drivers and non-drivers. Analysis of collected
data revealed that collisions associated with these
two groups are 98% and 2%, respectively (Figure 9).
As shown in Figure 9, 98% of the work zone traffic
collisions were associated with driver errors (i.e.
unsafe starting/backing up, unsafe speed, following
too closely, running red lights/stop signs, wrong
side of the road, auto right-of-way, improper turning,
unsafe lane changes, unsafe speed or DUIs). Among
the most common human errors are unsafe speed for
existing conditions (30%), automobile right-of-way
(16%), improper turning (13%) and disregarded traffic
signs/signals (11%).
Figure 9: Primary Collision Factors
In an effort to compare the primary collision factors
during the daytime and nighttime periods, information
depicted in Table 3 was prepared. As shown in this table,
four major factors cause more nighttime collisions.
These factors are DUIs, driving on the wrong side of
the road, running red lights/stop signs and following too
closely. Other factors, such as unsafe speed conditions,
improper turning, auto right-of-way and unsafe lane
changes, also cause more daytime collisions. According
to the inspected reports, no nighttime accidents were
attributed to unsafe starting/backing up and/or factors
other than drivers. This indicates that 100% of nighttime
accidents are attributed to human errors. While the
explanation of the very high DUI nighttime incidents
is obvious, more research is required to explain the

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Accident Patterns in Road Construction Work Zones
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
Table 3: Comparison of Collision Factors
Primary Collision Factor
Daytime
Nighttime
Contribution (%)
Contribution (%)
DUI
1
21
Wrong Side of Road
3
4
Ran Red Light/Stop Sign
8
20
Following Too Close
1
4
Unknown
3
6
Unsafe Speed for Conditions
32
21
Improper turning
16
4
Auto Right-of-Way
17
12
Unsafe Lane Change
8
4
Other
5
4
Unsafe Starting/Backing
3
0
Other Than Driver
3
0
difference between daytime and nighttime collision
factors. It should be noted that although Figures 3 and 4
indicate that nighttime traffic volume tends to be much
lower than that associated with daytime (about 1000
vph versus 16,000 vph), the results shown in Table 3
indicate that most identified collision factors cause more
nighttime accidents. This observation is considered
to be true when keeping in mind that nighttime traffic
volume is about 7% only of daytime (Figures 3 and 4).
Involved with Other Objects
Figure 10 shows that the majority of collisions were involved
with another motor vehicle (i.e. 85%). 11% of collisions
involved fixed and other objects that may include animals,
barriers, walls, and raised medians. While collisions with
pedestrians and bicyclists contributed 3%, collisions with
other vehicles contributed 4%.
Figure 10 depicts that 98% of work zone traffic collisions
results in property damages and injuries. Furthermore, one
fatality was reported between 1999 and 2009. It should be
noted that property damage expenses were not reported,
Weather and Roadway Surface Conditions
Figures 11 and 12 show that most of work zone related
traffic collisions (82%) occurred when the weather was
Figure 10: Objects Involved in Collisions
clear, and reveals no significant impact on work zone
related traffic collisions. Furthermore, only 3% of the
work zone traffic collisions occurred under inclement
weather conditions, and less than 5% took place when
the road surfaces were not dry. Therefore, it could be
concluded that these weather and road condition related
factors were not particularly significant in causing work
zone traffic collisions.

Accident Patterns in Road Construction Work Zones 55
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
Figure 11: Effect of Weather Conditions Figure 13: Effect of Traffic Control Devices
Figure 12: Effect of Road Conditions
Presence and Functionality of Traffic Control Devices
Figure 13 shows that 98% of traffic collision reports
indicated that traffic control device was either
functioning or not a factor in the collision. Only 2%
of all work zone related traffic collisions experienced a
non-presence or malfunction of traffic control devices.
It should be noted that according to the Collision
Investigation Manual, traffic control devices include
traffic signals, regulatory, warning, and construction
signs. Traffic control devices exclude striping and
officers or other persons directing traffic.
Roadway Classification
Figure 14 shows that 98% of work zone traffic collisions
occurred on principal (eight divided lanes), major (six
divided lanes), primary (four divided lanes) and secondary
(i.e. 4 undivided lanes) arterials, while 2% occurred on local
residential streets (two undivided lanes). The maximum
capacities of principal, major, primary, secondary arterials
and local streets are 60,000, 45,000, 30,000, 20,000 and
4,000 vehicles per day, respectively.
Figure 14: Collisions
vs. Roadway Classification
Gender and Unlicensed Drivers
Figure 15 shows 427 drivers were involved in the 204
traffic accidents that took place in construction zones.
The number of drivers involved in each accident ranged
from one to five, who were classified as males, females
and has not met the California State Age requirements
yet. The percentages of these driver categories are 58%,
36% and 6%, respectively.
Figure 15: Collisions vs. Gender and Unlicensed Drivers

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Accident Patterns in Road Construction Work Zones
Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org
REFERENCES
This paper focused on the analysis of accidents
that occur in the road construction zones that did
not have enough attention within the construction
research community, and findings in this domain
were described in recent publications as lacking
and insufficient. It focused on collision factors and
environments reported in California Highway
Patrol (CHP) reports. The results of this study
show that 98% of road work zone accidents result
in injuries and property damages. About 0.5%
of these types of accidents involved fatalities.
Most of these accidents occur during daytime in
summer months, and Tuesdays were associated
with the highest number of accidents. Rear-end
collisions were found to be the most common
type of accidents (i.e. 34%), followed by right-
angle (i.e. 27%) and sideswipes (i.e. 20%). 98% of
accidents were attributed to human errors such as
unsafe speed and improper turning. Comparisons
between the primary collision factors between
daytime and nighttime revealed that DUIs,
diving on the wrong side of the road, running
red lights/stop signs and following too closely
cause more accidents during nighttime. About
6% of accidents involved unlicensed drivers, who
have not met state age requirements yet. The
study found that while 85% of the construction
zone related traffic collisions involved vehicles
only, 3% involved pedestrians and bicyclists.
Unfavorable lighting/weather conditions and
wet roads did not significantly influence work
zone traffic collisions. 2% of the accidents were
partially attributed to malfunction and/or the
non-presence of traffic control devices. While
most accidents (i.e. 98%) occurred on arterials
within the city, very few (i.e. 2%) occurred on
local streets. Although this paper highlighted
many factors that contribute to and/or result
from traffic collisions in road construction work
zones, more research efforts are needed. Further
studies could explore related information, from
contractors’ perspectives, such as sections of work
zones in which accidents occurred, compliance of
contractors to the standard dimensions of work
zone segments, type of work being done and
whether sudden changes in pavement elevations
were existed before and/or after the accidents took
place. It is also believed that minimizing traffic
collisions in road construction zones is a shared
responsibility between many involved parties,
including contractors, owners and road users, and
extensive research work is needed to ameliorate
the knowledge in this field.
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Accident Patterns in Road Construction Work Zones 57
Fall 2015 — Volume 39, Number 02
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Fall 2015 — Volume 39, Number 02
The American Institute of Constructors | 700 N. Fairfax St., Suite 510 | Alexandria, VA 22314 | Tel: 703.683.4999 | www.professionalconstructor.org