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OCR for page 80
80 c. Work on shoulder or median Crashes by project type (paving, bridge work, night work, d. Intermittent or moving work etc.) e. Other Crashes by work zone type (lane closure, diversion, shoul- 4. Workers present? der work, etc.) Crash reduction strategies in work zones must first of all be Once these summaries are available, the following compar- effective for the type of road being worked on. Crash reduction isons should be made: factors are not known for work zone crash reduction strategies, but can be estimated for no-work zone conditions. For exam- Work zone rates to non-work zone rates for road type and ple, if shoulder rumble strips have a 0.80 CRF outside of work type of work. zones (i.e., result in a 20 percent reduction in run-off-road Work zone rates to non-work zone rates for work zone crashes), then a rough estimate of their effectiveness in work type zones is the same 0.80 CRF. All fatal crashes to work zone fatal crashes Different levels of analysis can be undertaken depending Total crashes to work zone crashes on the types of crash, roadway, and work zone information All fatal and injury crashes to work zone fatal and injury available. Four levels of analysis are discussed based on data crashes availability as follows: In addition to these comparisons, the following analysis Level 1 Analysis crash data include a work zone flag/ should be completed for a sample of the construction projects variable, a complete highway inventory is available, and the completed in the current year: location and date of all work zones from construction, maintenance and permits (utility) sections are available to Number of crash reports coded as work zone crashes link with the highway inventory. versus the number of crashes found by query using Level 2 Analysis crash data include a work zone flag/ location and date variable and a roadway inventory is available, but there is Determine the number of crashes that were related to work no work zone file. activity Level 3 Analysis crash data include a work zone flag/ variable, but there is no work zone file or highway inventory. One type of analysis that is done by the Ohio DOT is Level 4 Analysis crash data do not include a specific shown in Exhibit X-1. This exhibit shows 15 long-term inter- variable indicating a work zone crash, but other fields such state projects, the duration and length of each project, and an a traffic control device or object struck contain information average AADT for the project. The projects were constructed that can infer that the crash is a work zone crash. No work during 2002. zone file or highway inventory is available. With this information, crash rate is determined for each proj- ect and an average crash rate is computed for all 15 projects Level 1 Analysis (1.68 crashes/mvm as shown in Exhibit X-1). Fatality and fatal The Level 1 analysis can be the most complete because data plus injury rates can also be computed. A free-flow comparable is available on the boundaries and duration of each work rate is also computed for 15 projects using crash data from 1999 zone, the highway inventory can be searched for physical to 2002. While details for each project are not available from Ex- characteristics of the road where the work zone was located, hibit X-1, the free-flow projects should be comparable in road and crashes identified as work zone crashes can be analyzed type and they could be the same roadway before construction. and compared to total accidents. The AADTs listed would normally come from the highway This analysis also can be used to compute exposure num- inventory file, but the work zone AADTs should be determined bers for work zones and to compare crash rates for work zone from counts made during the work zone operations. and non-work zone conditions. The list below shows the At this level of analysis, crash rates for sections within a proj- types of analyses that can be completed for Level 1. ect can be computed by using the work zone file. Exhibit X-2 compiled by the Ohio DOT shows comparison of work zone Summarize the following types of crashes: sections versus pre-work zone 3-year averages for the same section. Note that 3-year averages were taken for the same Crashes by road type months (4/1511/15) in order to remove seasonal effects of Crashes by type of work (construction, maintenance, and crashes from any comparisons. utility) The results of the Level 1 analysis should be detailed Crashes by crash type enough to point to crash reduction strategies. Road types

OCR for page 80
Exhibit X-1. Historical crash data analysis (Ohio DOT).