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What's
a Work Zone?
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Sections 1051 and 2002a of the Intermodal Surface Transportation Efficiency Act of 1991 specifically direct the secretary of transportation to develop uniform accident reporting for fatalities, injuries, and certain specified accident types, including work-zone accidents. In 1992, the National Transportation Safety Board (NTSB) issued a report that recommended that FHWA revise the work-zone reporting system to distinguish between construction vehicles and other vehicles simply traversing the work zone. NTSB also recommended that FHWA standardize the work-zone data elements for all states.
The current lack of a uniform definition of work zone and of what constitutes a work-zone accident creates a broad disparity in work-zone accident reporting in the United States. An unpublished study in Michigan indicated that as many as 77 percent of accidents occurring within the limits of four selected work zones were not recorded as work-zone accidents.
The information resulting from a safety analysis of work zones would be used in two areas. Transportation planners should be aware of the safety implications of construction work so that the information can be included in the impact studies of projects under consideration. Second, by increasing our knowledge of work-zone accidents, highway engineers can better design the traffic control plans for work zones.
Parallel
Efforts
One goal of the FHWA effort was to combine the efforts
of various groups involved in the issue of work-zone definition. These
groups include: the National Highway Traffic Safety Administration (NHTSA),
which is involved in creating Guideline for Minimum Uniform Crash Criteria;
the American National Standards Organization (ANSI), which has an accident-classification
standard used by states and law enforcement agencies; the American Road
and Transportation Builders Association (ARTBA), which has initiated a
task force to examine the data needs in work zones; the American Association
of State Highway and Transportation Officials (AASHTO); and the Associated
General Contractors of America (AGCA). Representatives from each of these
involved organizations, which, in this article, are referred to as the
work-zone partners, worked with an FHWA task force to develop an acceptable
set of definitions.
Key Issues in a Standardized Definition of Work Zone
Differences in Terms
In the past, one major hurdle in gaining nationwide
approval of a definition of work zone and work-zone accident was that
different agencies define the various elements of the roadway differently.
Even when agencies agree in concept, they may state their definition in
a different manner due to their pre-established terminology. For example,
the term "trafficway" is defined by ANSI as the entire right-of-way, including
median and shoulder. However, AASHTO does not recognize the term "trafficway"
and uses the terms "highway, street, or road" to denote the same concept.
Based on feedback from representatives of the involved organizations,
FHWA and the work-zone partners determined that the differences in terms
should simply be noted in the definition. This was finalized after the
realization that the involved organizations tended to agree on the fundamental
types of information that should be collected in work zones even though
they may use different terms.
Accident Versus Crash
The terms "accident" and "crash" have been used loosely
and often synonymously when dealing with safety analysis. ANSI deals solely
with the term "accident" and has defined it as follows: "An accident is
an unstabilized situation which includes at least one harmful event."
ANSI does not currently define "crash"; however, there is an effort underway
to do so. According to the chair of the Committee on Motor Vehicle Traffic
Accident Classification, ANSI views an accident as something that is somewhat
preventable and a crash as either a deliberate act or an act of God. NHTSA's
Guideline for Minimum Uniform Crash Criteria, however, uses the
term "crash." Instead of attempting to resolve this issue, the term "accident"
was used with a reference to the use of the term "crash" by NHTSA.
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Defining the Work Zone
A number of attempts have been made to broaden the
definition of work zone to include the line of traffic that often builds
up as a result of the work zone. However, by including the queues as part
of the work zone, the physical limits of the work zone would be ever changing.
This would create problems for an analyst who wishes to place the boundaries
of the work zone on their geographic database of roads. FHWA and the work-zone
partners determined that the definition of work zone should be as absolute
as possible. The inclusion of work-zone-related accidents that are outside
of the work zone would then be considered through the definition of a
work-zone accident.
Defining the Limits of the
Work Zone
Perhaps the simplest way to define the limits of the work
zone would be to say that it extends from the initial upstream sign to
the last downstream sign. However, many of the short-term stationary and
mobile work zones are not well suited to meet this criteria.
The Manual on Uniform Traffic Control Devices (MUTCD) states, "The advance warning may vary from a single sign or flashing lights on a vehicle to a series of signs in advance of the temporary traffic control zone transition area." Also, many of the short-term stationary and mobile work zones do not use an "End of Road Work" sign; they simply use a channeling device for the length of the project. Therefore, it was determined to define the boundaries as extending "from the first warning sign or flashing light on a vehicle to the END ROAD WORK sign or the last traffic control device." It had been suggested that the work zone not require an advance warning device; however, MUTCD makes it very clear that advance warning signs or flashing lights on a vehicle are required for all road work activities.
Work-Zone-Related Accidents
FHWA and the work-zone partners agreed that the definition
of a work-zone accident should include accidents that occur as a result
of traffic queued before or after the work zone. However, there are differing
opinions as to whether a differentiation should be made between accidents
that occur in the work zone but have nothing to do with work-zone activities
and accidents that are a direct result of the work-zone activities.
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An unpublished report from the Texas Transportation Institute (TTI) indicated that the current policy of coding all accidents that occur in work zones as work-zone accidents grossly overestimates the number of accidents that are a result of road construction. TTI indicated that as few as 12 percent of all accidents occurring in Texas work zones were actually related to the work zone.
The issue, however, is in determining how much of a contribution must be attributable to the work zone before an accident should be considered as work-zone related. Through discussions with data analysis experts, FHWA determined that a "work-zone related" category would be desirable; however, the data would be very suspect given the wide range of responses that could be received from law enforcement officials. For instance, a vehicle that had an accident in a work zone after being cut off by another vehicle in the taper area may be coded as a work-zone-related accident by one police officer and totally unrelated to the work zone by another police officer.
The proposed definitions were written to include all accidents occurring inside the work zone and work-zone-related accidents occurring outside of the work zone. It is suggested that agencies who wish to single out work-zone-related accidents should use the proposed definitions in conjunction with data elements that describe the work-zone-related function.
Latest Draft of Work-Zone Definitions
Representatives of the interested groups - including AASHTO, ANSI, and many others - met in Washington, D.C., in November 1998 to discuss the proposed work-zone definitions. A few minor changes were suggested, but the six groups represented at the meeting generally agreed that they were comfortable with the following proposed definitions with a list of inclusions and exclusions.
Work Zone
A work zone is an area of a trafficway with highway construction,
maintenance, or utility-work activities. A work zone is typically marked
by signs, channeling devices, barriers, pavement markings, and/or work
vehicles. It extends from the first warning sign or flashing lights on
a vehicle to the "End of Road Work" sign or the last traffic control device.
A work zone may be for short or long durations and may include stationary
or moving activities. Inclusions:
1
The AASHTO term equivalent to roadway is traveled way.
2 The AASHTO term equivalent to trafficway is highway, street,
or road.
Work-Zone Accident
A work-zone accident is a traffic accident1
in which the first harmful event occurs within the boundaries of a work
zone or on an approach to or exit from a work zone, resulting from an
activity, behavior, or control related to the movement of the traffic
units through the work zone.
Inclusions:
1
The NHTSA term equivalent to accident is crash.
2 The AASHTO term equivalent to roadway is traveled way.
3 The AASHTO term equivalent to trafficway is highway, street,
or road.
Implementation of Nationwide Work-Zone Definition
The work-zone definition will be submitted to the ANSI Committee on Motor Vehicle Traffic Accident Classification for review and possible inclusion in the Manual on Classification of Motor Vehicle Traffic Accidents. It is anticipated that as the law enforcement community begins to adapt to the work-zone definition, the state and federal data analysis entities will adjust to the change in the work-zone information being collected.
The draft definitions will be submitted to the AASHTO Traffic Engineering subcommittee as well as to a number of other interested organizations in the hope that a consensus can be reached. Finally, the draft definitions will be published in an upcoming edition of the Federal Register in an attempt to gain feedback from the public.
The biggest challenge that must be overcome now is changing the current practices for data recording and reporting to accept the proposed definitions. Once the challenge of implementation begins, we may find that the development of the definitions turned out to be the easiest part of the process.
J. Dan Turner is a highway research engineer in FHWA's Office of Safety Research and Development at the Turner-Fairbank Highway Research Center in McLean, Va. Turner is responsible for research dealing with traffic control devices and work zones. He has both a bachelor's and a master's degree from the University of North Carolina at Charlotte. He is a registered engineer-in-training in North Carolina.
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