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53 same, the user will need to make the decision based on best Consider treatments with known effectiveness meas- judgment. ures (proven treatments) using either Procedure 1, 2A, 7. Add new treatments, new targets, or new approaches or 2B as appropriate, depending on the types of data (e.g., inclusion of safety treatments in normal mainte- available. Determine the crash/injury reduction nance or rehabilitation efforts) until the available achieved and compare it to the established crash/injury funding is used. reduction goal. If the goal has not yet been met, proceed In Procedures 1, 2A and 2B, an iterative process is used to Step 2. until sufficient treatment types and locations are selected 2. Consider tried treatments to supplement the proven ones. such that the established crash reduction goal can be This step would involve consideration of treatments reached. In Procedure 3, without effectiveness measures without known effectiveness that have been used exten- for the treatments, it is not possible to verify whether or sively by highway or driver/vehicle agencies (tried treat- not a specific set of treatment types and treatments will ments). If it is possible to estimate the effectiveness of these meet the established goal. Therefore, the best that can be treatments based on imperfect information, then proceed done is to proceed in selecting treatment types and treat- to Step 3; otherwise, proceed to Step 4. ments until the available budget for safety improvement 3. Estimate the effectiveness of tried treatments if possible, has been fully committed. The total benefit of the selected and analyze them using the appropriate procedure above. program will not be forecastable, but the success of the This step involves attempting to estimate the effective- program can be determined by evaluations conducted ness of treatments without known CRFs or AMFs. Note after its implementation. that estimating treatment effectiveness is very difficult and can lead to poor treatment choices unless the estimates are re- alistic. This estimation was not suggested in Procedure 3 Procedure 4 Choosing Treatments and for this reason. It is only suggested at this point since the Target Populations in Emphasis Areas for user has already considered all proven treatments before which Some Candidate Treatments Have reaching this stage. It is suggested that the following guide- Known Effectiveness Estimates and Other lines be used in making such estimates: Treatments Do Not a) In general, be as conservative as possible. Very few treat- In many situations, users considering a safety improvement ments can be expected to affect crash frequency by more program in a particular emphasis area will need to consider than 1525 percent. both treatments that have known effectiveness measures and b) When possible, formulate an effectiveness estimate that treatments that do not. In this situation, it is recommended that is applicable to particular target crash types only, not to the user give priority to treatments that have known effective- total crashes. ness measures (proven treatments). Treatments that have been c) Base estimates for tried treatments on CRFs for similar used extensively but for which effectiveness measures are treatments if they exist. not available (tried treatments) should then be considered. Once effectiveness is estimated, apply Procedure 1, 2A or Experimental treatments may have a modest role in a safety 2B as appropriate, depending on the types of data avail- improvement program, particularly if the program is structured able. Determine the crash/injury reduction achieved in to evaluate the effectiveness of the experimental procedure. Steps 1 and 3 combined and compare it to the established The recommended planning approach in this situation is a crash/injury reduction goal. If the goal has not yet been hybrid of Procedures 1, 2A, 2B, and 3 described above. met, proceed to Step 4. 4. Consider additional tried treatments. For treatments for which reliable effectiveness measures Procedure cannot be estimated in Step 3, apply Procedure 3 to select 1. Determine if proven treatments can meet the established additional treatment types and target locations until all goal. available funds have been budgeted.