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OCR for page 68
68 SECTION VIII Unsafe Driver Actions Planning Programs Related edgeline and centerline rumblestrips may help alert the to Reducing Crashes Involving drowsy driver and also may help keep impaired drivers from Distracted and Fatigued Drivers leaving their travel lane. The traffic engineer should use his or and Unbelted Vehicle Occupants her judgment to determine which subset of crashes or driver population may be affected by each treatment application This section of the guide presents a strategy for selecting being considered. The benefits of a given treatment may be treatments to reduce crashes involving distracted and fa- greater, and therefore worth more investment, when other tigued drivers and unbelted vehicle occupants. As noted ear- target populations or crash types are also positively impacted. lier, it is assumed that a safety planning team has selected one Procedure 3, as described in Section III, outlined an ap- or more of the above emphasis areas as part of its safety plan proach for selecting strategies in the absence of known crash and has established a "stretch goal" as described in Section I. effectiveness estimates (AMFs or CRFs) and B/C ratios. This Four procedures for choosing treatment strategies and target procedure is designed for use with treatments where crash re- groups were described in Section III of this guide. Three of duction effectiveness has not been established. Many of the these procedures require known estimates of effectiveness treatments related to unsafe driver actions fall into this cate- (crash reduction and benefit-costs) for some or all of the se- gory, and that procedure will be presented below. lected strategies in other words, that the treatments have The safety planning team is strongly urged to carefully known CRFs or AMFs. However, in general, the two guides review the material in each of the pertinent guides before considered here identified strategies that do not completely beginning the planning process. These user-population meet this requirement even though many of the strategies are oriented guides are found within NCHRP Report 500: Guid- supported by compelling evidence of significant crash reduc- ance for Implementation of the AASHTO Strategic Highway tion. The major exceptions to this situation are a subset of Safety Plan. The specific volumes pertinent to this section on proposed strategies related to distracted and fatigued drivers, illegal driving acts are: strategies related to improving the roadway to prevent lane departure, and intersection crashes involving these drivers. Volume 11: A Guide for Increasing Seatbelt Use (11) Some of these strategies could be analyzed using procedures Volume 14: A Guide for Reducing Crashes Involving Drowsy 1, 2, and 2A since AMFs are known. The user is referred to and Distracted Drivers (14) Sections IV and V if analyzing those strategies with known ef- fectiveness. What is generally lacking for other strategies in A link to these downloadable guides can be found in these two guides are precise estimates of the magnitude of the http://safety.transportation.org/guides.aspx. The planning crash reduction that could be used in the development of an team is also encouraged to review NCHRP Report 501 (18) for estimated B/C ratio. The latter, in turn, also requires known a detailed description of an integrated problem identification estimates of treatment costs and effects on crash severity, and safety planning process. which are often lacking. Thus, we know in some cases that the treatment reduces crashes but not by how much or in terms General Strategic Considerations of net cost-benefits. It should be noted that some strategies aimed at drowsy As noted earlier, data for estimating precise AMFs, CRFs drivers are also beneficial for impaired drivers. For example, and B/C ratios for many of the driver-oriented and vehicle-