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Shared-Track: A Handbook of Examples and Applications 71 Table 19. Summary of basic route and service parameters. Parameter Units Value Days of Operation Days 250 Shared Route Length Miles 8.3 Number of Grade Crossings Number 8 Grade Crossings per Mile Number 0.96 Peak Service Interval Minutes 15 Off-Peak Service Interval Minutes 30 Route, traffic and ridership data. Basic route information was taken from the descriptions ear- lier in this chapter. The specific inputs to the model are given in Table 19. Note that the analysis is performed for nonholiday weekdays only. It is assumed that freight trains only will operate on these days, and risks to train occupants at weekends are not affected. However when a more advanced signal system is installed to reduce and offset the risks from freight operations, this also will reduce risks of collisions between passenger trains during any weekend and holiday operations. The numbers of passenger train trips/day are summarized in Table 20. Option 1 lacks early morning and evening trips, which are added in Options 2, 3, and 4. In Options 2, 3, and 4 some midday and evening trips are freight-exposed, in that they pre- cede, follow or pass an active freight train, including switching an en route industry track. Freight activity and the corresponding number of freight-exposed trips in Options 2, 3 and 4 are sum- marized in Table 21. In full temporal separation (Option 1), no passenger trips are exposed to risk from freight operations. The higher number of freight-exposed trips in Option 2 is due to the lower freight operating speed and the extra time needed to make the moves over diamonds. In this option the freight exposure is to intrusion accidents and the diamond crossing movements. Average train occupancy, needed in the calculation of injuries and fatalities, is displayed in Table 22 for each operating period. Accident frequency and consequences for train-train collisions were estimated from FRA acci- dent data for commuter rail collisions. Intrusion collision incidents are based on FRA data for existing mixed passenger and freight operations. Data for all other accident scenarios, including grade crossing collisions, derailment and obstruction also were derived from FRA studies. Results and Risk Analysis Findings Table 23 shows estimated numbers of accidents for each accident scenario. Tables 24 and 25 provide the injury rate and fatality rate per million passenger miles respectively. Details of the accident scenarios are in the Task 10 Report. Results show a slight increase in the number of collision accidents in Option 2 compared with Option 1 (due mainly to more trips), and a substantial reduction in collision accidents for Options 3 and 4, in spite of the increased train miles and the increase in intrusion collision risks that arise from concurrent passenger and freight operations. The change is primarily due to the Table 20. Passenger trips by time of day. Traffic Parameter Option 1 Option 2, 3 and 4 Peak Service, Peak Direction 23 23 Peak Service Reverse Direction 23 23 Midday 28 28 Early Morning and Evening 0 24
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Table 21. Exposure of passenger trips to freight activity. Parameter Option 2 Option 3 Option 4 Operating Parallel operations Shared single track Shared double track Regime Midday Freight One round trip, no One round trip, Same as Option 3 Activity industry switching switches one industry track Evening Freight One round trip, One round trip, Same as Option 3 Activity switched both industry switches one industry tracks track Midday Freight- 12 8 8 Exposed Trips Evening Freight- 10 8 8 Exposed Trips Table 22. Occupancy of passenger train by operating period. Total Occupants (Standees in Brackets) Operating Period Option 1 Option 2, 3, and 4 Peak Period Peak 153 (18) 151 (11) Direction Peak Period Reverse 19 19 Direction Midday 75 (2) 79 (3) Early Morning and 0 29 Evening Table 23. Estimated FRA-reportable train accidents over 10 years for each option. Option 1 Option 2 Option 3 Option 4 Accident Scenario Full Temporal Concurrent Concurrent Concurrent Separation Separate Shared Shared (Base Case) Single Tracks Single Track Double Track Train-Train Collisions 0.181 0.171 0.079 0.039 Intrusion Collisions 0.009 0.021 0.021 0.024 Diamond Collisions 0 0.023 0 0.014 All Train Collisions 0.190 0.215 0.099 0.077 Derailments 0.092 0.122 0.122 0.122 Obstructions 0.198 0.262 0.262 0.262 Grade Crossings 1.032 1.366 1.366 1.366 Total Accidents 1.51 1.94 1.85 1.81 Train-Miles (millions) 1.54 2.03 2.03 2.03 Accident Rate per 0.98 0.96 0.91 0.89 million train miles Table 24. Estimated rates of passenger injuries for each option. Option 1 Option 2 Option 3 Option 4 Accident Scenario Full Temporal Concurrent Concurrent Concurrent Separation Separate Shared Shared (Base Case) Single Tracks Single Track Double Track Train-Train Collisions 2.989 2.458 1.203 0.595 Intrusion Collisions 0.075 0.134 0.134 0.152 Diamond Collisions 0 0.007 0 0.004 All Train Collisions 3.064 2.60 1.34 0.75 Derailments 0.226 0.255 0.255 0.255 Obstructions 0.097 0.110 0.110 0.110 Grade Crossings 0 1.141 1.141 1.141 Total Accidents 4.40 4.09 2.84 2.23 Passenger miles 125.7 141.5 141.5 141.5 (millions) Injury Rate per million 35.02 28.96 20.09 15.70 passenger miles