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36 overall goal that has been established. If the goal is ori- 7. Sum all expected crash injury reductions for all chosen ented to fatal and injury target crashes, then these will be treatment types and chosen target locations and com- accumulated. If the goal is total target crashes, then these pare that total to the established goal. will be accumulated. 8. Add new treatments, new targets or new approaches The summing of goal-related crashes or injuries will be (e.g., inclusion of safety treatments in normal mainte- done by estimating the annual number of such target nance or rehabilitation efforts) until the goal is met. crashes for all segments (windows) chosen for treatment Again, the example draft plan presented at the FHWA (after correction for treatment gaps). While it was rela- web site (http://safety.fhwa.dot.gov/roadway_dept/docs/ tively simple to add in the additional crashes from the lanedeparture/index.htm) provides additional discussion of "gap-filling" segments with a full inventory file in Proce- this option. dure 1, this is not as simple here, since the network screen- ing program used in this procedure does not output seg- Procedure 2B Choosing Roadway-Based ments other than those meeting the crash frequency Treatments and Target Populations When threshold. It is suggested that in this case, the annual num- Treatment Effectiveness Is Known and ber of goal-oriented crashes from the identified treatment Neither Mileposted Crash Data nor segments be used to estimate the additional number that Detailed Inventory Data Are Available would occur on the added treatment gap segments. As noted above, the network screening program can be The following text identifies the data needed for conducting developed to output the total number of target crashes in Procedure 2B, followed by the individual steps in the proce- each window chosen for treatment and the (approximate) dure. Note again that since no mileposted crash data exist, this length of each chosen treatment window. The estimate procedure will only allow the user to identify entire routes of annual target crashes (or injuries) per mile in these within a given jurisdiction as potential treatment routes, but chosen windows is: not segments of routes. It will also not allow the user to target the treatments to specific locations along the route. Annual Target Crashes CI = Sum of window lenggths Data Needs Where: The data needed for Procedure 2B are less than required in Sum of all target cra ashes in either of the previous two procedures. Major differences in- chosen windows clude the fact that no inventory or traffic data are required, and Annual Target Crashes = Number of years of crash data that the crashes do not have to be "mileposted" to a specific used in the sample location on a specific route. However, each crash record must contain information on the county or local jurisdiction and the The user can also manually calculate the number of miles name of the route/street where the crash occurred. of treatment gaps that he or she adds for treatment in Step 3. The number of goal-related target crashes for these A specified effectiveness level (CRF or AMF) for each segments can be estimated by multiplying the total length treatment to be examined. of these new segments by CI in the above formula. See discussion of this issue under Procedure 1. 5. Repeat the above steps for each potential treatment type. A computerized crash data file which includes sufficient As in Procedure 1, the above steps are then repeated for crash details to isolate target crash types that will be af- the second and subsequent potential treatment types. In fected by each treatment (run-off-road, head-on crashes each case, critical crash frequencies are calculated for each and run-off-road on curves), and potential target popula- roadway class, the network screening is used to identify tions. Each crash record must contain a county or jurisdic- treatment segments, and corrections are made for treat- tion name where the crash occurred, and the name of the ment gaps. However, a final correction is needed for route or road where the crash occurred. segments that have been identified for more than one "Route length" information that will provide the length treatment type, as detailed in the following step. in miles of each road or route within a county or local 6. Correct for multiple treatments on the same segment. jurisdiction that is a potential target for any treatment, The user will again need to correct for multiple treat- or at least the approximate length. ments on the same segment. The same rationale and pro- If this information is not available in the user's files, it may cedure followed in Procedure 1 will be followed here. (See be available from other sources including road maintenance Step 8 of Procedure 1). records, and can be scaled from maps if necessary.

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37 Unit cost for each treatment both original implemen- 6. Estimate the expected crash injury reductions on all the tation costs and annual maintenance costs identified target routes. See discussion of this issue under Procedure 1. Just as in Procedure 1, the results of this step will be used in Step 9 below in determining whether or not the goal for the jurisdiction is reached. Here, for each treat- Procedure ment route identified at the end of Step 5, the user will The following steps are those that would be followed for need to determine the annual number of crashes and in- choosing among roadway-segment treatments with known juries that will be reduced by this treatment. This will be effectiveness and targeting these treatments to entire routes done by summing up all pertinent crashes or crash in- in a jurisdiction. juries for all routes to be treated, and then multiplying this annual total by the estimated effectiveness level for 1. Develop critical crash frequencies for each candidate the treatment under consideration. treatment type and roadway class of interest. The "crit- ical frequency" is the annual frequency of target CI reduction = (CI) Eff crashes per mile that, if treated, will result in crash- Where: injury reductions whose economic benefit will exceed CI = Annual "goal-related" crashes or crash injuries on implementation costs by some factor. the routes chosen The same formula and information presented above Eff = treatment effectiveness under Step 2 of Procedure 1 will be used here. 2. Link target crashes to each route in each jurisdiction Just as in Procedure 1, the definition of goal-related (but not to a specific point on the route). crashes or injuries is, as implied, based on the nature of This will require computer sorting of crashes by each the overall goal that has been established. If the goal is named route. Some manual effort will be required to oriented to "fatal and injury" target crashes, then these correct misspelled names and to group routes or streets will be accumulated. If the goal is total target crashes, that have multiple names. The output of this program then these will be accumulated. will be a listing of target crashes sorted by route name. The annual estimate of potentially treatable crashes or Note that multiple years of crashes can be used, and in- injuries can be extracted from the spreadsheet output in deed the procedure will be more accurate if more than Step 3. For the routes chosen, divide the total crashes on 1 year's crash data (e.g., 3 to 5 years) are used. If multi- each route by the number of years of data, and then sum ple years are used, there may be situations where a route across all chosen routes. was renamed during the period. If so, both crashes with 7. Repeat the above steps for each potential treatment type. the original and new name should be accumulated As in Procedures 1 and 2A, the above steps are then re- under one route name. peated for the second and subsequent potential treat- 3. Develop a spreadsheet that contains the count of target ment types. crashes for each route (one route per row), along with 8. Correct for multiple treatments on the same route. the mileage for that route. The user will again need to correct for multiple treat- It may be possible for the computer program used to ments on the same route. In general, the same rationale and sort the crashes in Step 2 to output this count for each procedure followed in Procedure 1 will be followed here. route. If not, the counts can be made manually. The final (See Step 8 of Procedure 1.) However, in this case, cor- output of this step is a spreadsheet containing a total rections are made on a route-basis rather than a route- count of target crashes and the length in miles for each segment basis (i.e., either one treatment is specified for a route under consideration. given route and that route is removed from other treat- 4. Calculate the annual crash frequencies per mile for ment groups, or a correction in effectiveness is made for the each potential route. second and subsequent treatment on the same route). If a spreadsheet is used, this is a simple step in which the 9. Sum all expected crash injury reductions for all chosen crash count is divided by the route length times the num- treatment types and chosen target routes and compare ber of years of crashes used. that total to the established goal. 5. Identify routes to be treated by determining which have 10. Add new treatments, new targets, or new approaches calculated annual frequencies per mile that exceed the (e.g., inclusion of safety treatments in normal mainte- developed critical crash frequencies per mile. nance or rehabilitation efforts) until the goal is met. This is a comparison of the output of Step 4 with the Again, the FHWA Sample Plan for lane departures "critical frequencies" defined in Step 1. (24) provides additional discussion of this option.