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14 number of crashes of a particular type with the average cost Following is a list of treatments that were rated by the survey for that type of crash (based on Council et al., 2005), we can respondents among the top 15 in terms of importance, but get the crash harm associated with that particular crash were not selected in the short list: type. However, in attempting to do this, we realized that in order for this crash harm analysis to be useful, we would need · Coordinate signals along routes or corridors. The research to include measures of both the expected size of the effect team felt that this treatment is mainly used to improve (before the evaluation) and either the proportion of signal- traffic flow and reduce delays and not specifically imple- ized intersections or the proportion of signalized-intersection mented to improve safety. For this reason, it was felt that crashes that might be affected by each treatment to be assessed. the development of an improved safety-based CMF would For example, while left-turn phasing and split phasing can not significantly affect use of this treatment, and that a true both be targeted to reducing crashes involving left-turning evaluation would need to trade-off safety findings and delay vehicles, they might affect a different proportion of the left-turn findings, something beyond the scope of this project. In crashes, and more importantly, they might be only suitable addition, the evaluation of this treatment is expected to be for use at a different proportion of signalized intersections. difficult since (1) finding coordinated systems that had no Since there is no national inventory of signalized inter- coordination before might be difficult, and (2) the coordi- sections, it was not possible to develop the needed estimates. nated system might change over time, making it difficult to Thus, we assumed that the inputs from users concerning clearly specify a treatment corridor. treatment priorities give some indication of the size of the · Delineate turn path inside an intersection. The research remaining signalized-intersection problem to be solved in team felt that the effects of this treatment on safety are small their jurisdiction--the "problem size" for them. and hence would require a substantial number of sites to Based on the project team's review and assessment of the first statistically detect this expected change in safety, and hence, three of these four aspects (i.e., the data assessment required research would not be cost-effective. follow-up phone interviews with the states), the list of potential · Utilizing crossing guards for school children. The expo- treatments was narrowed down to the following: sure to this treatment is limited (i.e., during school open- ings, closings, and during lunch), reducing the number of · 17.2 A1: Split phasing potential crashes for study. Thankfully, pedestrian crashes · 17.2 A1: Adding protected left-turn phasing* are rare events. Hence, hundreds if not thousands of sites · 17.2 A2: Modifying the change interval* would be needed in order to do an effective study. In addi- · 17.2 A3: Restricting or eliminating turns at the intersection tion, conducting an evaluation will require data on pedes- · 17.2 A7: Remove unwarranted signals trian crossing volumes that the research team found very · 17.2 B1: Adding left-turn lanes* difficult to find based on previous studies that have been · 17.2 B1: Lengthening left-turn lanes conducted. Hence, the research team felt that allocating re- · 17.2 B2: Improving right-turn channelization sources to evaluate this treatment will not be an efficient · 17.2 B4: Modify intersection skew use of the project budget. · 17.2 C2: Improve sight distance · 17.2 D1: Advance Warning Signs for Red Signal Phone Calls to Selected Agencies · Improvements in signal visibility and conspicuity including 17.2 D2: Backplates Based on survey information on available data, the follow- 17.2 D2: Adding reflective sheeting to backplates ing agencies were initially contacted for follow-up telephone 17.2 D2: Increase signal head size to 12 inches* interviews: 17.2 D2: Installing louvers and visors 17.2 D2: Installing additional signal heads* · City of Grand Junction, CO; 17.2 D2: Installing far side left-turn signals · City of Memphis, TN; · City of Overland Park, KS; Note that the treatments designated with asterisks in the · City of San Diego, CA; previous list have existing CMFs which have been judged to · City of Scottsdale, AZ; be of at least "medium high" predictive certainty. However, · City of Sparks, NV; they continued to be included on the potential treatment listing · City of Tempe, AZ; since (1) they are rated highly in the survey, and (2) the research · Broward County DOT, FL; team feels that the existing CMFs could be further improved · Lee County DOT, FL; depending on the availability of data, e.g., to provide variable · Lexington-Fayette Urban County Government, KY; CMFs for different implementation circumstances. · Washtenaw County Road Commission, MI;
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15 · Arkansas State Highway and Transportation Dept; · Do you keep records of installation for these treatments? · Hawaii DOT; If yes, what is the format? · Kansas DOT; · Who maintains the crash data? · Minnesota DOT; · What years of crash data are available? · Missouri DOT; and · How are the locations of crashes referenced in the data? · South Carolina DOT. · In what format are the traffic data maintained? · In what format are the traffic counts presented? Raw data? These agencies were selected because they indicated they had ADT? AADT? a sizeable amount of installations of one or more of the treat- · Are turning movement counts available? ments of interest and they did not indicate any problems with · What source of information is available on roadway/ their crash data in their survey response. The project team inter- intersection geometry? viewed representatives from each of the agencies that responded · Are there any known problems with any of the data? to the follow-up contact (indicated in bold in the previous list). · Was the protected left-turn phasing used when the inter- A series of questions were asked regarding the installation data, section was built or was it added after the intersection was crash data, traffic data, roadway data, and individual treat- already operational? ments. Examples of the questions asked included: · Are the advanced warning signs dynamic or static?