Prioritization Procedure for Proposed Road–Rail Grade Separation Projects Along Specific Rail Corridors (2019) / Chapter Skim
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53 Methodology for Adjusting the USDOT Accident Prediction Value This appendix describes the methodology used to identify the variables to adjust the USDOT accident prediction value. The methodology is illustrated with the development data for crossings with gates when Scale Option A is used.
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54 Warning Device Number of Crossings Number of Crossings with Accidents Number of Accidents XB 1,964 55 58 FL 1,472 39 41 Gates 3,434 236 271 Table B-1. Number of crossings and accidents in development data (Illinois)
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55 To validate the above results, the same procedure was carried out on the validation data set that was created. In this data set, there are 224 crossings with a severity value of 2 or more.
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56 Adjustments to Gated Crossings Using Multiple Variables For each of the crossings in the database, an adjustment was added on the basis of the combination of the variables considered, the normalized value, and the weight assigned. This adjustment was of the form adjusted USDOT accident prediction value for crossing USDOT accident prediction value normalized value of variable 1 w ii i i n p∑ = + = where wi is the weight corresponding to the ith variable and n is the number of variables used (in this case n is 2 or 3)
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57 C um ul at ive S ev er ity V al ue s of C ro ss in gs Position of Crossing in Sorted List variable Figure B-1. Cumulative severity values of crossings in model development data.
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58 Variable Name Categories Scheme Used Weight Applied Maximum timetable train speed ≤10 0.1 0.017 10–20 0.2 20–30 0.3 30–40 0.4 40–50 0.5 50–60 0.6 60–70 0.7 >70 0.8 Distance to nearby highway intersection <75 1 0.017 75–200 0.5 200–500 –0.5 >500 –1 Crossing surface Unconsolidated 1 0.011 Timber 0.5 Asphalt 0 Rubber –0.5 Concrete –1 Table B-13. Corrective variables normalized gated crossings (severity scale of 5, 3, 1)
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59 Variable Name Categories Scheme Used Weight Applied Maximum timetable train speed ≤10 0.1 0.018 10–20 0.2 20–30 0.3 30–40 0.4 40–50 0.5 50–60 0.6 60–70 0.7 >70 0.8 Distance to nearby highway intersection <75 –1 0.001 75–200 –0.5 200–500 0.5 >500 1 Table B-16. Variables and weights for severity, Scale Option B (F/I/P = 10/4/1)
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