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OCR for page 45
45 $2,000 Involved Vehicle Intrusions per 100 Crash Costs due to Worker- $1,500 Hours per Mile $1,000 $500 $0 0 50000 100000 150000 200000 250000 Roadway AADT Daytime Conditions Nighttime Conditions Figure 26. Estimated costs of worker-involved vehicle intrusion crashes during work activities involving temporary lane closures. countermeasure ideas, as well as to estimate the expected crash have limited opportunity to further improve conditions or reductions that may be achieved by the countermeasures. safety through this strategy. In contrast, agencies whose poli- cies, standards, and procedures are lacking would have the potential to improve conditions and achieve measurable Strategies to Improve Driver safety benefits. In reality, differences between agencies may Compliance with Work Zone be much more subtle, with examples of both good and not- Traffic Controls so-good work zone implementations evident in either juris- Good compliance with traffic laws and regulations in work diction. One could hypothesize that the higher rear-end crash zones is critical to obtaining and maintaining a high level of percentages cited in the previous chapter are one way in safety and orderly, efficient traffic flow. The NCHRP guid- which a lack of sign credibility manifests itself, leading to ance document lists the following three specific strategies higher levels of inattentive or unsuspecting drivers who dis- under this category that are believed to positively influence regard the advance warning signs of a work zone. work zone safety: The remaining two strategies in this category both relate to the effectiveness of law enforcement to ensure driver com- Improved credibility of signs, pliance with traffic laws and regulations in the work zone. Enhanced enforcement of traffic laws in work zones, and Essentially all states utilize law enforcement personnel in some Improved application of increased driver penalties in work fashion in their work zones (55). However, the manner in which zones. enforcement personnel are used varies. Some agencies empha- size the use of enforcement for active identification of violators The first strategy, improving the credibility of signs, em- and issuance of citations in the work zone, whereas others phasizes the importance of ensuring that the posted signing emphasize the use of enforcement presence for visibility and in work zones meets current federal and state standards and attention-getting purposes during times when workers are out reflects actual conditions in the work zone. Efforts to ensure in travel lanes at high risk next to moving traffic (55). Currently, that the information presented via static and dynamic signing there is little objective evidence to suggest which approach is is as accurate and as current as possible at all times is also more effective in promoting safety, although an ongoing believed to result in improved driver compliance and, ulti- NCHRP project is examining this issue in more detail (56). mately, work zone safety (52). Although this statement is in- Overall, there is some evidence to suggest that additional tuitively obvious, the extent to which these efforts can be enforcement presence in both work zones and non-work quantified in terms of potential work zone crash reductions zone locations can improve safety (57, 58, 59, 60). However, or improvements is limited. Theoretically, agencies with good the amount of the improvement from a crash reduction per- policies and standards in place as well as effective procedures spective varies due to differences in enforcement strategies to monitor and quickly correct deficiencies in the field would used, the amount of additional enforcement used, and the

OCR for page 45
46 $15,000 Reduction in Crash Costs per 100 25% Reduction in Crashes $12,500 Hours per Mile $10,000 $7,500 $5,000 $2,500 10% Reduction in Crashes $0 0 50000 100000 150000 200000 250000 Roadway AADT Work Zone Active with Temporary Lane Closures Work Zone Active without Temporary Lane Closures Work Zone Inactive Figure 27. Possible reductions in crash costs due to enforcement presence: daytime conditions. type of crash analysis used, making comparisons across studies expected to influence the potential of all crashes to occur. difficult. Conservatively, crash reductions of up to 25 percent Both a 25 percent reduction and an even more conservative in the vicinity of enforcement may be possible. If reductions 10 percent crash cost reduction are shown. of this magnitude are achieved, the question becomes whether A review of some recent memorandums of understanding the costs of providing that enforcement are outweighed by (MOUs) between highway and enforcement agencies to pro- the reduction in crash costs that occur. Depending on the vide work zone enforcement support indicates hourly costs characteristics of the work zone, the answer appears to be yes. of between $25 and $60 per hour per officer (between $2,500 Using the California crash models again for illustrative pur- and $6,000 per 100 hours). The costs may be higher in other poses, Figure 27 and Figure 28 present the crash cost savings states. These costs can be compared to the crash cost savings that would be achieved under the various work conditions estimated in the figures to determine the AADT level at which during daytime and nighttime periods. Total crash costs, not the savings begin to exceed these costs (for a work zone 1 mile just the additional crash costs due to work zone presence, are in length). At the lower end of the pay scale, it appears that used in the analysis because enforcement presence would be enforcement can be economically justified under all work $15,000 Reduction in Crash Costs per 100 $12,500 Hours per Mile $10,000 25% Reduction in Crashes $7,500 $5,000 $2,500 10% Reduction in Crashes $0 0 50000 100000 150000 200000 250000 Roadway AADT Work Zone Active with Temporary Lane Closures Work Zone Active without Temporary Lane Closures Work Zone Inactive Figure 28. Possible reductions in crash costs due to enforcement presence: nighttime conditions.