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61
Data Element Considerations of Work Zone Modification to project diary pages to specifically request lane
Exposure Information closure information, and the inclusion of this item in con-
struction management software where project diary data are
The previous discussion notes the importance of capturing kept, would be an important first step.
roadway and certain work zone characteristic information
present at the time of a crash; this information is typically not
captured in agency roadway inventory databases because of Recommended Work Zone Crash
the temporary nature of the work zone. In addition to these Data Analysis Methods
types of event-based data elements, there is a need for agen- In the most general terms, work zone crash data can be
cies to begin to establish mechanisms to gather and organize used for ongoing monitoring functions or for detailed after-
data pertaining to work zone exposure information. These the-fact (post-hoc) investigations to quantify and/or test the
exposure data elements are needed to properly normalize statistical significance of various crash-related hypotheses.
crashes into appropriate rate-based measures so that they can The monitoring function can be for a particular project, or it
be consolidated across multiple work zones and compared in can be for a particular crash type across a district, region, or
various ways. even state. For example, project engineers often maintain an
The data elements needed or desired for exposure estima- informal awareness of the crashes occurring in their particu-
tion purposes include those pertaining to traffic and to specific lar project (either informally by discussions with local law
characteristics of the work zone itself. Suggested elements and enforcement or by regularly obtaining actual hard copies of
attributes include the following: crash reports occurring in the work zone) as a way of check-
ing for any obvious safety problems that need immediate
· Traffic volumes and characteristics (ADTs, hourly volumes, attention in the work zone. Likewise, some states maintain a
and vehicle mix); running total of the number of fatalities or the number of cer-
· Work zone length (overall and by sections with similar tain types of crashes occurring in work zones throughout the
geometric features); year to compare against similar year-to-date totals in previ-
· Work zone duration (duration of phases, hours of work ac- ous years. Meanwhile, post-hoc investigations are typically
tivity, and times and durations of capacity restrictions); and carried out to determine the amount of crash increase occur-
· Highway worker and equipment exposure (number of ring in work zones overall or of a particular type, to evaluate
workers and equipment present, and location of workers/ the effect of a particular design feature or operating strategy
equipment within the work zone). upon crashes, or to evaluate the effectiveness of a particular
countermeasure implemented to address a particular crash
Currently, few agencies actively collect work zone traffic issue. The analyses performed as part of this research are
data, although the increased use of work zone ITS technologies examples of these post-hoc investigations.
now provides an opportunity to do so with greater frequency. The Ohio Department of Transportation is one agency that
On the other hand, much of the proposed data pertaining to has formalized its efforts to monitor crashes in its significant
work zone exposure are already within the potential grasp of work zones (76). For those work zones selected for monitor-
many highway agencies. Daily project diaries already provide ing, the agency divides the projects into 0.5-mi segments and
spaces to document times of work activity, equipment and compares crashes occurring in each segment with the average
workers present, locations of work activities, etc. As agencies rate of crashes that had occurred in those segments in the pre-
move toward electronic storage of daily project information vious 3-year time period. Those segments where crashes ap-
(using the AASHTO Trns·port SiteManager or other con- pear abnormally high are targeted for further assessments of
struction management software), the opportunity does exist the possible underlying factors that may be contributing to the
to more easily extract this type of data for use in exposure higher-than-normal crash frequencies. An example of the
estimation. The challenge will be in ensuring adequate docu- type of analysis generated through this effort is provided in
mentation levels of these data elements. As part of this re- Figure 29. Crashes are examined both by location and by time
search, thousands of pages of such diaries were reviewed. The to identify unusual trends. A key component of this process
extent to which those elements were consistently reported in is the commitment of personnel resources by the Ohio DOT
the diaries varied widely. to manually collect hard-copy crash reports from the law en-
Other data elements, most notably lane closures that tem- forcement office at each project every 2 weeks and to enter
porarily restrict the capacity of the roadway, do not have a that data into the spreadsheets used for analysis.
specific field in the inspector diary but are typically docu- A comparison of some of the opportunities and challenges
mented in the narrative portion of the diary. Capturing these associated with monitoring and post-hoc investigations of
data at the present time is thus extremely time consuming. work zone crashes is provided in Table 25. Review of the
