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68 CHAPTER 6 Conclusions AMFs are a key component of existing procedures used by However, even with this amount of concentrated effort, state and local transportation agencies to choose and target there remain a number of critical safety treatments, includ- safety treatments and of a series of new safety analysis tools ing many ITS treatments, for which credible AMFs do not being developed to make these safety decision processes even exist. As described in Chapter 2, the research team developed more effective and efficient. AMFs can be developed from an and used a detailed procedure for ranking AMFs needing de- analysis of crash data, usually in a before-after evaluation, velopment. The procedure included not only an assessment and from combinations of information from prior research of the current status of AMF knowledge (the level of predic- studies. While there have been decades of effort aimed at tive certainty) but also priority ratings by state DOT users, an developing credible AMFs, there have been surprisingly few estimate of crash-related harm possibly affected by the treat- developed that are of a quality that withstands critical scrutiny. ment, knowledge of ongoing or future research that might However, in the past 10 years, there has been greatly in- develop AMFs, and the current availability of needed evalua- creased emphasis on the development of credible AMFs. With tion data. Table 20 provides a listing of treatments that are this emphasis has come greatly increased funding, both in the considered to be high-priority targets for future development NCHRP program funded by AASHTO and in FHWA's re- based on this ranking methodology. Clearly, others would be search program. NCHRP funded the development of the added if another ranking method was used. NCHRP Report 500 guides, which have captured information In summary, this project has verified, modified, or devel- on safety program effects from existing research literature in 20 oped 35 AMFs that are perceived to be of high or medium- different roadway, driver, and vehicle emphasis areas, in sup- high quality. These have been documented in formats that are port of the implementation of the AASHTO Strategic Highway usable by both practitioners and researchers. These AMFs are Safety Plan. In response to knowledge needs cited in a group of the primary project outputs. The project has also docu- the NCHRP Report 500 guides, FHWA is funding a continuing mented a process that can be used with future analysis-driven series of scientifically sound evaluations of low-cost treatments expert panels, and notes from the detailed discussions of the for roadways. NCHRP is also funding a series of projects aimed two expert panels that were part of this effort can be provided at development and publication of the Highway Safety Man- to others. This material should be helpful in future efforts to ual, including a detailed "current knowledge" section that cap- develop or improve AMFs for treatments for which no AMF tures AMFs from published literature, the aforementioned could be developed in this research. Finally, a procedure for project to develop crash prediction tools and AMFs for rural ranking needed AMF research was developed and docu- multilane highways, and the aforementioned project to de- mented--a procedure incorporating not only state DOT user velop similar tools and AMFs for suburban/urban arterials. and researcher opinions and knowledge of the quality of The project effort described in this report is the final major AMFs in the published literature, but also a method for esti- AMF development effort recently funded by NCHRP. As mating the crash-related harm that might be affected by each shown in Table 18 (see Chapter 5) AMFs have been verified, treatment. An approach combining these factors could be modified, or developed here. When published this year, the used in more global efforts to prioritize roadway safety re- Highway Safety Manual will provide a larger list of AMFs. search needs in general.
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69 Table 20. High priority treatments needing AMF development in future research. High Priority Treatments Overall Ranking for (Gray shading indicates high ranking in user survey) Future Research* Intersection Treatments Channelize right turns MH Install dynamic advance warning flashers "Red Signal Ahead" MH Provide signal coordination MH Prohibit left turns MH Segment Treatments Add a travel lane MH Add shoulder rumble strips (two-lane/others) MH Add edgeline rumble strips MH Eliminate left turns at driveways MH Remove roadside obstacles (including urban) MH Flatten sideslopes MH Add advance curve warning signs/on pavement markings H Add midblock pedestrian signal MH Install raised crosswalk (non-intersection) MH * H = High, MH = medium high