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Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation (2010)

Chapter: Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation

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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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Suggested Citation:"Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
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12 Flange climb derailment can occur due to excessive lateral forces acting on the wheel as a vehicle negotiates a curve. A common remedy for flange climb derailment in curves is to install guard rails on curves to provide additional resistance to flange climbing. The fundamental flange climb derailment mechanism was investigated in TCRP Report 71, Volume 5 (2). In this Chapter, dynamic curving simulations were con- ducted on four types of transit vehicles by using the NUCARS program. The L/V ratio and flange climb distance criteria proposed in the previous TCRP project (2) were applied to the simulation results. Guidelines for guard rail installation were produced based on these analyses. 4.1 Simulation Cases The track geometries were represented both as smooth track without track irregularities (as designed) and also with a “down and out” perturbation in the middle of the curve. The “down and out” perturbations consisted of a combination of track geometry irregularities that were of a magnitude at the limit generated based on the track standards from several transit systems. This consisted of a downward vertical cusp on the high rail combined with an outward lateral alignment cusp on the high rail and an inward cusp on the low rail of a magnitude sufficient to ensure that the maximum permitted gage was not exceeded. These irregularities had a 31-ft wave- length with a cosine shape, with three levels of severity of perturbations, as displayed in Figures 19 through 21. Table 4 lists the amplitudes of the track perturbations. The most severe perturbation (Level 3) is typical of the maintenance limit for low-speed operation in rail yards. The Level 1 perturbation represents a typical limit for a high speed on a main line. These perturbations were placed in the middle of a number of left hand curves with curve radii from 100 ft to 3,000 ft, and 1-in. superelevation. The vehicle running speed was 15 mph on yard track, and speeds corresponding to 4.0 in. and 7.5 in. cant deficiency overbalance speeds on main-line tracks for different radius curves (see Table 5). The wheel/rail friction coefficient has a large effect on the potential for derailment; therefore, all simulation cases were carried out for W/R friction coefficients of 0.3, 0.4, 0.5 and 0.6. 4.2 Transit Rail Cars Figure 22 shows the steady-state curving results for a transit rail car (Type 1) on a yard track without perturbations. The wheel L/V ratio on tight curves with a radius less than 500 ft increases when the W/R friction coefficient increases. The vehicle derailed on curves with a radius less than or equal to 250 ft at a friction coefficient of 0.6, which indicates that a guard rail is needed even on a perfect track without perturbations. As expected, the dynamic curving L/V ratios on a perturbed track without a guard rail increase with the W/R friction coeffi- cient and the amplitude of the perturbations (See Figures 23 and 24). The L/V ratios are generally higher than those in the steady curving conditions. The dynamic L/V ratios approach or exceed the Nadal limit (shown as a solid line) at a friction coefficient of 0.5. The vehicle derailed for all simulated cases (100 to 3,000 ft radii curves) with a friction coefficient of 0.6 and Level 3 perturbations. There are many factors that lead to flange climb derailment. Three of them have the most critical effects: wheel flange angle, friction coefficient, and perturbation amplitude. As Figure 22 shows, even without perturbations, wheel flange climbing can still occur because of a lower (63°) flange angle and a higher friction coefficient (0.6). Tests and simulations show that the friction coefficient plays a critical role for derailment. If the W/R friction coefficient can be controlled to remain under 0.4 with reliable lubrication devices, guard rails are not needed for this type of vehicle (Figures 22 through 24). However, many factors lead to the variation of the friction coefficient such as weather conditions, unreliable rail lubrication, new trued wheel surface roughness, C H A P T E R 4 Transit Vehicle Flange Climb Derailment Simulation

13 The likelihood of flange climb derailment is rare if the wheel climbs on the rail with distance less than 3 ft. • For curves with radii greater than 755 ft: – The L/V ratio limit equals the Nadal limit; and – Flange climb distance limit equals 5 ft. The reasons for using a longer flange climb distance criteria for curves with radii larger than 755 ft are the following: • The steady-state axle AOA on curves with radii larger than 755 ft is normally less than 5 milliradians (mrad); • The L/V ratio limit decreases with the increase of AOA and converges to the Nadal value as the AOA becomes larger than 10 mrad (2); and • The flange climb distance decreases when the AOA increases, and converges to a value (2). Based on these criteria, for the Type 1 transit rail car with a 63° flange angle running on yard track with Level 3 pertur- bation, the guard rail should be installed on curves with radii less than 3,000 ft to prevent flange climb derailment because the L/V ratios with a 3-ft window (for curves with radii less than or equal to 755 ft) or a 5-ft window exceeded the Nadal value. However, if the track perturbation maintenance improves to the Level 2 standard on yard tracks, only curves with radii less than or equal to 755 ft need to be guarded, as Figure 25 shows. Maintenance on a main-line track is normally better than maintenance on a yard track. Correspondingly, the allowable running speed on a main-line track is higher than the allowable running speed on a yard track. The Type 1 transit rail car either derailed or the L/V ratio and flange climb distance exceeded the criteria values on all simulated curves at speeds of 4 or 7.5 in. cant deficiency on Level 3 perturbed tracks, which indicates such maintenance levels cannot be tolerated on main-line track for this vehicle. The situation was a little better for Level 2 perturbations where the L/V ratio had less than a limit of 4 in. cant deficiency speed on curves with radii larger Level 1 -2.50 -2.00 -1.50 -1.00 -0.50 0.00 360 380 400 420 440 460 Distance (ft) Pe rt ur ba tio n (in .) Lat Right Lat Left Vert Right Figure 19. Track perturbation, Level 1. Level 2 -2.50 -2.00 -1.50 -1.00 -0.50 0.00 360 380 400 420 440 460 Distance (ft) Pe rt ur ba tio n (in .) Lat Right Lat Left Vert Right Figure 20. Track perturbation, Level 2. Lat Right Lat Left Vert Right Level 3 -2.50 -2.00 -1.50 -1.00 -0.50 0.00 360 380 400 420 440 460 Distance (ft) Pe rt ur ba tio n (in .) Figure 21. Track perturbation, Level 3. and W/R wear conditions; all of these factors are hard to control. Table 6 lists the W/R friction coefficients measured on TTCI’s track. The measured rail friction coefficient at normal conditions can be higher than 0.55 but are seldom above 0.6. To ensure a reasonable safety margin, the simulation results with a friction coefficient of 0.6 are used in this study to make judgments about whether guard rail installations are needed. The simulation results with a friction coefficient of 0.55 were also conducted for a less conservative application. Based on the conclusions and findings in TCRP Report 71 (2), the following criteria were used for making judgments about whether a guard rail is needed: • For curves with radii less than or equal to 755 ft or for vehicles with independent rotating wheel: – The L/V ratio limit equals the Nadal limit. There is no flange climb derailment risk if the L/V ratio is less than the Nadal limit; and – The flange climb distance limit equals 3 ft. This criterion is less conservative than the above L/V ratio criterion.

14 Curve Radius (ft) Superelevation (in.) 4.0 in. Cant Deficiency Speed (mph) 7.5 in. Cant Deficiency Speed (mph) 100 1.0 11.14 14.52 250 1.0 17.62 22.96 320 1.0 19.93 25.97 500 1.0 24.92 32.46 755 1.0 30.62 39.89 955 1.0 34.43 44.87 1,145 1.0 37.70 49.13 2,000 1.0 49.83 64.93 3,000 1.0 61.03 79.52 Table 5. Overbalance running speed on curves. 0 0.2 0.4 0.6 0.8 1 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—63° Figure 22. Wheel L/V ratio of a Type 1 transit rail car with steady-state curving 15 mph, no guard rail. Perturbation Level Left (Low) Rail Lateral Perturbation Amplitude (in.) Left (Low) Rail Vertical Perturbation Amplitude (in.) Right (High) Rail Lateral Perturbation Amplitude (in.) Right (High) Rail Vertical Perturbation Amplitude (in.) 1 –0.13 0 –0.50 –0.50 2 –0.63 0 –1.00 –1.25 3 –1.25 0 –2.00 –1.25 Table 4. Track perturbation amplitude.

15 0 0.2 0.4 0.6 0.8 1 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—63° Figure 23. Wheel L/V ratio, Type 1 transit rail car, Level 2 perturbations 15 mph, no guard rail. 0 0.2 0.4 0.6 0.8 1 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—63° Figure 24. Wheel L/V ratio, Type 1 transit rail car, Level 3 perturbations 15 mph, no guard rail. Track Location Inside Outside Weather Condition Date Time R36 Post Marker 0.43 0.52 Sunny 2/25/2007 10:30 AM R36 Post Marker 0.41 0.46 Cloudy 3/08/2007 9:00 AM R36 Post Marker 0.40 0.44 Sunny 3/15/2007 9:10 AM RTT R36 Post Marker 0.46 0.45 Sunny 3/16/2007 8:40 AM R165 Post Marker 0.50 0.56 Sunny 2/23/2007 10:00 AM TDT R165 Post Marker 0.32 0.37 Sunny, Soap and Water Spray on Track 2/23/2007 11:00 AM 7.5° curve 0.48 0.46 12° curve 0.43 0.43 WRM 10° curve 0.49 0.47 Sunny 2/19/2007 12:20 PM WRM 10° bypass curve 0.44 0.45 Sunny 3/20/2007 1:30 PM 7.5° curve 0.48 0.5 7.5° curve 0.43 0.44 WRM 12° curve 0.46 0.5 Cloudy 3/21/2007 10:20 AM Table 6. Measured W/R friction coefficients (tribometer readings) on TTCI track.

16 Friction Coefficient 0.6 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 100 300 500 700 900 1100 Curve Radius (ft) Le ad A xl e Hi gh R ai l W he el L /V NADAL Limit 7.5 inch CD, no pert 7.5 inch CD, pert1 7.5 inch CD, pert2 4.0 inch CD, pert2 15 mph, pert2 Figure 25. The wheel L/V ratio of a Type 1 transit rail car with a 0.6 friction coefficient and a 63° flange angle.* *Refer to Table 5 for the different speeds corresponding to 7.5-in. cant deficiency (CD). Friction Coefficient 0.5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 100 300 500 700 900 1100 Curve Radius (ft) Le ad A xl e Hi gh R ai l W he el L /V NADAL Limit 7.5 inch CD, no pert 7.5 inch CD, pert1 7.5 inch CD, pert2 4.0 inch CD, pert2 15 mph, pert2 Figure 26. The wheel L/V ratio of a Type 1 transit rail car with a 0.5 Friction Coefficient and a 63° Flange Angle.* *Refer to Table 5 for the different speeds corresponding to 7.5-in. cant deficiency (CD). than 2,000 ft. For Level 1 track perturbations, the L/V ratio exceeded the Nadal value on curves with radii less than or equal to 500 ft at 7.5 in. cant deficiency speed, as Figure 25 shows. Under such conditions, no guard rails are needed for curves with radii larger than 500 ft for the Type 1 transit rail car. Another way to decrease the flange climb derailment risk is to decrease the W/R friction coefficient. As Figure 26 shows, if the friction coefficient is 0.5, for the Type 1 transit rail car, the guard rail should be installed on yard curves with radii less than or equal to 300 ft, and main-line curves with radii less than or equal to 500 ft at a 7.5 in. cant deficiency speed. However, controlling the friction coefficient to less than 0.5 on curves in a consistent and reliable way may be difficult during actual service. A measured worn rail profile was used in the simulation to investigate the effect of worn rails on flange climb derailment. Figures 27 through 29 show that the L/V ratio for the worn rail case is less than that of the new rail case shown in Figures 22 to 24. These results imply that simulations using new W/R profiles will lead to conservative conclusions. An investigation of worn W/R profiles on freight car flange climb derailment (5) also showed a similar phenomena because most wheels and rails wore into a steeper flange contact angle. Another common practice to decrease flange climb derail- ment risk in transit systems is to increase the wheel flange angle. As discussed in the previous TCRP Report 71, Volume 5 (2), increasing the flange angle increases the Nadal flange climb limit. Case studies were conducted for the Type 1 transit rail car

17 0 0.2 0.4 0.6 0.8 1 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—63° Figure 27. Wheel L/V ratio, Type 1 transit rail car, steady-state curving, 15 mph, worn rail. R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft 0 0.2 0.4 0.6 0.8 1 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V Figure 28. The wheel L/V ratio, Type 1 transit rail car, perturbation Level 1, 15 mph, worn rail. R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft 0 0.2 0.4 0.6 0.8 1 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V Nadal—63° Figure 29. Wheel L/V ratio, Type 1 transit rail car, perturbation Level 3, 15 mph, worn rail.

using the same modeling parameters except for the wheelset dimensions and the 75° angle wheel profiles. Figure 30 shows the significant safety improvements made by using the 75° flange angle wheel compared with the 63° flange wheel (Figure 22), with all simulated steady-state curving L/V ratios far below the Nadal values. Figures 31 and 32 show that the dynamic curving L/V ratios of the Type 1 transit rail car with 75° flange angle wheels also increase as the perturbation increases. As Figure 30 shows, a steeper flange angle wheel increases the L/V ratio slightly com- pared with the 63° flange angle wheel. The improvement is because the NADAL value for the 75° flange angle is consid- erably higher than for the 63° flange angle. The use of a steep flange angle wheel reduces the flange climb derailment potential. Figure 33 shows that the L/V ratios for all the simulated cases at a speed of 15 mph and with Level 3 perturbations are less than the Nadal value. Therefore, no guard rail is needed on yard curves with radii larger than 100 ft for a vehicle with a 75° flange angle wheel running at a speed of 15 mph. However, the risk of derailment still exists under conditions of higher speeds and a poorly maintained track. As Figure 33 shows, the vehicle with a 75° flange angle wheel still derailed on curves with radii larger than or equal to 1,145 ft at a 7.5 in. cant deficiency speed because of excessive lateral impacts. The track has to be maintained with at least a Level 2 standard to allow a 7.5 in. cant deficiency running speed. The following conclusions for the Type 1 transit rail car can be drawn from the above analyses: • The flange climb derailment risk is very high for the Type 1 transit rail car with a 63° flange angle wheel. Guard/ restraining rails should be installed on the following: – Yard curves with radii less than 755 ft; the speed limit is 15 mph under Level 2 perturbations. 18 0 0.2 0.4 0.6 0.8 1 1.8 1.6 1.4 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—75° Figure 30. Wheel L/V ratio, Type 1 transit rail car, 15 mph, 75° flange angle, steady-state curving. 0 0.2 0.4 0.6 0.8 1 1.8 1.6 1.4 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Figure 31. Wheel L/V ratio, Type 1 transit rail car, 15 mph, 75° flange angle, perturbation Level 2.

– Main-line curves with radii less than 500 ft; the speed limit is 4 in. cant deficiency under Level 1 perturbations. • The flange climb derailment risk is significantly reduced by using 75° flange angle wheels. No guard rail is needed in yard, and the main-line speed limit can be 7.5 in. cant deficiency under Level 2 perturbations. • From a safety point of view, the 75° flange angle wheel is recommended for use in transit vehicles. 4.3 Light Rail Vehicles The light rail vehicle also benefits from the use of a steep flange angle (75°) wheel. As Figures 34 and 35 show, all simulated steady-state curving L/V ratios for the Type 1 light rail vehicle running on yard curves are far below Nadal values; the dynamic L/V ratios under Level 3 pertur- bations approach or exceed the Nadal value only with a friction coefficient of 0.6. Figure 36 shows the following for the Type 1 light rail vehicle with a 75° flange angle wheel: • The dynamic curving L/V ratios for the vehicle running at a speed of 15 mph under Level 3 track perturbations exceeded the Nadal value on curves with radii less than or equal to 755 ft. • The dynamic curving L/V ratios for the vehicle running at a 7.5 in. cant deficiency speed under Level 1 track per- turbations were below the Nadal value on all simulated curves. • The dynamic curving L/V ratios for the vehicle running at a 4.0 in. cant deficiency speed under Level 2 track pertur- bations exceeded the Nadal value on curves with radii less than or equal to 500 ft. 19 0 0.2 0.4 0.6 0.8 1 1.8 1.6 1.4 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—75° Figure 32. Wheel L/V ratio, Type 1 transit rail car, 15 mph, 75° flange angle, perturbation Level 3. NADAL Limit 7.5 inch CD, no pert 7.5 inch CD, pert2 7.5 inch CD, pert3 15 mph, pert3 Friction Coefficient 0.6 0 0.2 0.4 0.6 0.8 1.2 1 100 300 500 700 900 1100 Curve Radius (ft) Le ad A xl e Hi gh R ai l W he el L /V Figure 33. Wheel L/V ratio, Type 1 transit rail car, 75° flange angle, friction coefficient 0.6.* *Refer to Table 5 for the different speeds corresponding to 7.5-in. cant deficiency.

20 0 0.2 0.4 0.6 0.8 1 1.8 1.6 1.4 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—75° Figure 34. Wheel L/V ratio, Type 1 light rail vehicle, steady-state curving, 15 mph. 0 0.2 0.4 0.6 0.8 1 1.8 1.6 1.4 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—75° Figure 35. Wheel L/V ratio, Type 1 light rail vehicle, Level 3 perturbations, 15 mph. NADAL Limit 7.5 inch CD, no pert 7.5 inch CD, pert1 4.0 inch CD, pert2 15 mph, pert3 Friction Coefficient 0.6 0 0.2 0.4 0.6 0.8 1.2 1 100 300 500 700 900 1100 Curve Radius (ft) Le ad A xl e Hi gh R ai l W he el L /V Figure 36. Wheel L/V ratio, Type 1 light rail vehicle, friction coefficient 0.6.

Correspondingly, for the Type 1 light rail vehicle with a 75° flange angle wheel, the following was determined: • No guard/restraining rail is needed for the vehicle running at a speed of 7.5 in. cant deficiency on curves with radii larger than or equal to 100 ft if the track is maintained at a Level 1 perturbation standard. • Guard/restraining rails should be installed on the following: – Yard curves with radii less than 755 ft; the speed limit is 15 mph under Level 3 perturbations, and – Main-line curves with radii less than 500 ft; the speed limit is 4.0 in. cant deficiency under Level 2 perturbations. TCRP Report 71, Volume 5 (2) showed that the IRW is prone to flange climb derailment due to the lack of longitudinal creep forces. The simulation of the Type 2 low-floor light rail vehicle with an IRW in the middle truck was conducted to address the safety concerns for this type of vehicle. Figures 37 and 38 show that both steady-state and dynamic curving L/V ratios for all simulated cases are less than the Nadal values. Therefore, the low-speed curving performance on yard curves by the Type 2 light rail vehicle with a 75° flange angle IRW is even better than the performance by the Type 1 light rail vehicle that used solid axles for all trucks. Because the wheelset geometry and wheel profiles used by both types of light rail vehicles are exactly the same, the performance difference must be caused by the dif- ferent dynamic behavior between the solid axles and the IRWs, different vehicle structures, and the suspension characteristics. These two types of light rail vehicles behave differently, not only on low-speed curving, but also on high-speed curving. Figure 39 shows that the IRW L/V ratios generally increase with the running speed and result in flange climb derailment on 21 0 0.2 0.4 0.6 0.8 1 1.8 1.6 1.4 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—75° Figure 37. Wheel L/V ratio, Type 2 light rail vehicle, steady-state curving, 15 mph. 0 0.2 0.4 0.6 0.8 1 1.8 1.6 1.4 1.2 0.3 0.50.4 0.6 Friction Coefficient Le ad A xl e Hi gh R ai l W he el L /V R=100 ft R=250 ft R=320 ft R=500 ft R=755 ft R=955 ft R=1145 ft Nadal—75° Figure 38. Wheel L/V ratio, Type 2 light rail vehicle, Level 3 perturbations, 15 mph.

curves with radii greater than or equal to 955 ft at a 4.0 in. cant deficiency speed under Level 2 perturbations. The derailment was caused by resonance responses of the Type 2 vehicle at higher speeds. The Type 2 light rail vehicle with a 75° flange angle wheel can run safely at a 4.0 in. cant deficiency speed on curves with radii larger than 100 ft and Level 1 perturbations. 4.4 Summary of Flange Climb Derailment Simulations Dynamic curving simulations of the four types of transit rail cars and light rail vehicles with three different flange angle wheels (IRW for Type 2 light rail vehicles only) at 15 mph on yard track were conducted using the NUCARS program. Table 7 lists the radii of the curves where either the dynamic curving L/V ratio exceeded the Nadal value or the vehicle derailed with a 0.6 W/R friction coefficient. Curves with radii less than those shown in the following tables are recommended for guard rail installation. Table 8 lists the simulation results with a 0.55 friction coefficient for the less conservative guard rail installation application. Tables 9 and 10 list the dynamic curving simulation results on main-line curves with a 0.6 W/R friction coefficient and at speeds of 4.0 and 7.5 in. cant deficiency, respectively. The following conclusions can be drawn from the flange climb derailment simulations of Type 1 and 2 transit rail cars and light rail vehicles with various flange angle wheels: • There are many factors leading to flange climb derailment, but three of them have the most critical effects: wheel flange 22 NADAL Limit 7.5 inch CD, no pert 7.5 inch CD, pert1 4.0 inch CD, pert2 15 mph, pert3 4.0 inch CD, pert1 Friction Coefficient 0.6 0 0.2 0.4 0.6 0.8 1.2 1 100 1300500 1700900 29002100 2500 Curve Radius (feet) 3r d Ax le (IR W ) H igh R ail W he el L/V Figure 39. Wheel L/V ratio, Type 2 light rail vehicle, friction coefficient 0.6. Transit Rail Car Type 1 Transit Rail Car Type 2 Light Rail VehicleType 1 Light Rail Vehicle Type 2 Perturbation Level 63 70 75 63 70 75 63 70 75 63 70 75 1 R<=500* LTN** LTN R<=955 LTN LTN R<=500 R<=320 LTN R<=1,145 LTN LTN 2 R<=755 R<=320 LTN R<=2,000 R<=320 LTN R<=1,145 R<=955 R<=500 R<=3,000 R<=500 LTN 3 R<=3,000 R<=320 LTN R<=3,000 R<=320 LTN R<=3,000 R<=1,145 R<=755 R<=3,000 R<=3,000 LTN Note: *R<=320 indicates that the 3-ft window L/V ratios on curves with radii lower or equal to 320 ft exceeded Nadal values or the vehicle derailed. **LTN indicates that the L/V ratios of all simulated cases with curve radii from 100 to 3000 ft are less than Nadal values, and derailment is not expected. Table 7. Flange climb derailment on yard curves with a W/R friction coefficient of 0.6 at 15 mph. Transit Rail Car Type 1 Transit Rail Car Type 2 Light Rail Vehicle Type 1 Light Rail Vehicle Type 2Perturbation Level 63 70 75 63 70 75 63 70 75 63 70 75 1 R<=320 LTN LTN R<=500 LTN LTN R<=320 LTN LTN R<=320 LTN LTN 2 R<=500 LTN LTN R<=1,145 LTN LTN R<=955 R<=500 LTN R<=3,000 LTN LTN 3 R<=1,145 LTN LTN R<=1,145 LTN LTN R<=2,000 R<=755 LTN R<=3,000 LTN LTN Table 8. Flange climb derailment on yard curves with a W/R friction coefficient if 0.55 at 15 mph.

angle, W/R friction coefficient, and track perturbation amplitude. • Flange climb derailment risk decreases as the wheel flange angle increases: the larger the wheel flange angle, the smaller the guarded curve radius. • Flange climb derailment risk decreases as the W/R friction coefficient decreases: the lower the friction coefficient, the smaller the guarded curve radius. No guard rail is needed for all simulated vehicles if the friction coefficient can be controlled under 0.4. • Flange climb derailment risk increases as track perturbation increases; the smaller the track perturbation amplitude, the smaller the guarded curve radius. • TTCI recommends to adopt 75° flange angle wheels for both transit rail cars (Type 1 and 2) and light rail vehicles (Type 1 and 2) to prevent flange climb derailment. • From a safety point of view, the guard rail installation guidelines for the simulated two types of transit rail cars and two types of light rail vehicles (defined in Table 2 in the report) with recommended 75° flange angle wheels are listed below: – For yard curves (15 mph speed limit) with the most severe (Level 3, shown in Figure 21 in the report) track perturbations, these are the following guard rail instal- lation guidelines:  No guard rails are needed for Type 1 and Type 2 transit rail cars or Type 2 light rail vehicles.  Guard rails should be installed on curves with radii less than or equal to 755 ft for the Type 1 light rail vehicle. – For main-line curves, these are the following guard rail installation guidelines:  No guard rails are needed for Type 1 and 2 transit rail cars running at a 7.5 in. cant deficiency speed with Level 2 (Figure 20) track perturbations.  No guard rails are needed for Type 1 light rail vehicles running at a 7.5 in. cant deficiency speed with Level 1 (Figure 19) track perturbations.  No guard rails are needed for Type 2 light rail vehicles running at a 4.0 in. cant deficiency speed with Level 1 track perturbations.  Guard rails should be installed on curves with radii less than or equal to 500 ft for Type 1 light rail vehicles running at a 4 in. cant deficiency speed with Level 2 track perturbations.  Guard rails should be installed on curves with radii greater than or equal to 955 ft for Type 2 light rail vehicles running at a 4 in. cant deficiency speed with Level 2 track perturbations. • Vehicle curving performance is different from case-to-case due to many factors from vehicle and track aspects. The above guidelines and details in Tables 7 through 10 of the report could be used as a reference and applied by taking into account the specific vehicle/track features and running environment. 23 Transit Rail Car Type 1 Transit Rail Car Type 2 Light Rail Vehicle Type 1 Light Rail Vehicle Type 2 Perturbation Level 63 70 75 63 70 75 70 75 70 75 1 R<=500 LTN LTN R<=755 LTN LTN R>=1,145, <=2,000* LTN R>=1,145, <=2,000 LTN 2 R<=2,000 R<=320, 3,000 LTN R<=3,000 R<=250 LTN R<=3,000 R<=500 R<=3,000 R>=955 3 R<=3,000 R<=3,000 LTN R<=3,000 R<=755, >=2,000 R>=2,000 R<=3,000 R<=3,000 R<=3,000 R>=500 Note: *R>=1,145,<=2,000 indicates that the 5-ft window L/V ratios on curves with radii greater than or equal to 1145 ft, but less than or equal to 2,000 ft exceeded Nadal values or the vehicle derailed. Table 9. Flange climb derailment on main-line curves with a W/R friction coefficient of 0.6 at 4-in. cant deficiency. Transit Rail Car Type 1 Transit Rail Car Type 2 Light Rail Vehicle Type 1 Light Rail Vehicle Type 2 Perturbation Level 63 70 75 63 70 75 70 75 70 75 1 R<=500 LTN LTN R<=500 LTN LTN R<=320 LTN R>=755, <=2,000 R=2,000 2 R<=3,000 R<=320, >=2,000 LTN R<=3,000 LTN LTN R<=755, >=2,000 R<=500, =3,000 R<=3,000 R<=3,000 3 R<=3,000 R<=3,000 R>=955 R<=3,000 R>=755 R>=1,145 R<=3,000 R<=3,000 R<=3,000 R<=3,000 Table 10. Flange climb derailment in main-line curves with a W/R friction coefficient of 0.6 at 7.5-in. cant deficiency.

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Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation Get This Book
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TRB’s Transit Cooperative Research Program (TCRP) Report 71, Volume 7: Guidelines for Guard/Restraining Rail Installation explores two guard rail installation philosophies and the effects of vehicle types, wheel flange angle, wheel/rail friction coefficient, curve radius, cant deficiency, and track perturbation on flange climb derailments.

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