Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 58
58 If targeting is to be done by location, the treatment as applying the same treatment used with other user pop- could be targeted to counties, city areas, or routes/streets ulations. showing the highest total crash cost or frequency, coupled 7. Add new treatments, new targets or new approaches (e.g., with the analyst's judgment of potential differences in cost inclusion of improved signing and marking in normal between locations and technical and political issues. If the maintenance efforts) until the available funding is used. crash data are mileposted, the analyst could (1) link Without effectiveness measures for the treatments, it is crashes to routes and search for the locations of "clusters" not possible to verify whether or not a specific set of treat- of target crashes for possible treatment or (2) use a net- ment types and treatments will meet the established goal. work screening program similar to that described under Therefore, the best that can be done is to proceed in select- Procedure 2A to identify 1-mile sections with the highest ing treatment types and treatments until the available crash frequency or total crash cost. The windows identi- budget for safety improvement has been fully committed. fied by the network screening program could then be The total benefit of the selected program will not be fore- ranked by crash frequency or total crash cost to identify castable, but the success of the program can be determined priority locations. The analyst would then correct for by evaluations conducted after its implementation. "treatment gaps" using the same logic provided in Proce- dure 2A (see Section IV). If the crashes are not mileposted, Closure Good Data Produce Better Results but there is information available on jurisdiction and route, the analyst could link crashes to routes within the The assumption in this section has been that crash data are jurisdiction and calculate the total crash cost or number of available, but not necessarily other data such as roadway in- target crashes per mile by dividing the sum of the crash ventories. As is obvious in the procedures above, the availabil- cost or the sum of target crashes on that route by route ity of mileposted crash data will result in improved treatment length. The analyst could then rank the potential routes targeting, and the availability of linkable (and thus mileposted) for treatment based on this rate per mile, and choose the inventory data would further increase the analyst's ability to routes to be treated based on the highest rankings plus both choose treatment strategies and to target them. For ex- other technical and policy factors. ample, inventory data could provide detailed data not found in 6. Decide what to do with multiple treatments for the same crash data files on such items as signal timing, intersection subgroup or on the same segments/routes. layout, and street width, all of which are related to treatment The above steps could possibly produce subgroups, ge- strategies listed in the guides. ographic areas, roadway locations or routes within a ju- In like fashion, more detailed data on crash types would risdiction that could be treated with multiple treatments. greatly increase the analyst's ability to choose treatments, par- If the potential treatment strategies still under considera- ticularly for pedestrian and bicycle crashes. Such enhanced tion are characterized by different target crash types (e.g., data can be developed by a state or local jurisdiction using a left-turn intersection crashes vs. angle intersection tool known as Pedestrian and Bicycle Crash Analysis Tool crashes for older drivers), and if the crash data are mile- (PBCAT). For more information on this tool, go to http:// posted or include route information, the analyst could www.walkinginfo.org/pc/pbcat.htm. use the outputs of Step 5 above in making the treatment Finally, many of the special user-population strategies cov- choice. Step 5 would produce the total crash cost or crash ered in this section will be applied in local jurisdictions as well as frequency of each potential target subgroup or location. at the state level. Many local jurisdictions have or are consider- For each subgroup or location where multiple treatments ing officially or unofficially increasing the threshold for crash are possible, the analyst could compare the crash reporting which means they will be reporting fewer non-injury frequency or total crash cost for each of the different crashes. It should be noted that such a policy will likely greatly possible strategies. Total crash cost would be a much su- reduce the crash sample available for analysis in local jurisdic- perior criterion if the target crash types being compared tions, particularly for older and younger driver programs, since differ with respect to crash severity (e.g., turning crashes many of the crashes for these two groups will be non-injury vs. head-on crashes). If total crash cost or frequency for crashes. While pedestrian and bicycle crashes may be less one treatment strategy clearly exceeds total crash cost or affected, their numbers are usually so small in a local jurisdic- frequency for the other, the first would be a logical treat- tion that any decrease is problematic. Safety analysts are urged ment choice. If the total crash cost or frequency for the to consider such proposed threshold changes carefully and to different strategies is essentially the same, the analyst will bring the expected negative effects to the attention of decision need to make the decision based on best judgment, such makers.