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6 CHAPTER 3 Comparisons of Two Guard Rail Installation Philosophies To compare the two different guard rail installation philoso- derailment study (2). No simulations or analyses were made phies, the TTCI NUCARS vehicle-track dynamics computer for heavy rail vehicles, although the lightest weight heavy rail program was used to conduct steady-state curving simulations vehicles can have dimensions and wheel loads that are similar on a number of constant radii curves without perturbations to the Type 2 Transit Rail Car. to evaluate performance trends. Table 2 lists the parameters The Type 1 light rail vehicle represented a typical high-floor of the four types of transit vehicle models used in this project. articulated vehicle composed of two car bodies and three trucks, Figure 3 illustrates their structures and layouts. Since there as Figure 3(b) shows. The two car bodies articulated on the are no uniform definitions of "heavy rail vehicles," "transit rail middle truck and all three trucks have solid wheel sets. cars," or "light rail vehicles," this report adopts the customary The Type 2 light rail vehicle model was a typical articulated definitions used by most transits, which are the following: low-floor light rail transit vehicle. It was composed of three car bodies and three trucks, as Figure 3(c) shows. The end car Heavy Rail Vehicles: They are also referred to as commuter bodies were each mounted on a single truck at one end and rail and subject to FRA regulations. They normally have two connected to an articulation unit at the other end. The center trucks and examples include Metro North; LIRR; METRA car body was the articulation unit riding on a single truck (Chicago); SEPTA (Philadelphia, commuter service); equipped with independent rotating wheels. CalTran (California); MARC (Baltimore); and MBTA The track inputs included a number of left hand smooth (Boston). All these cars are designed to interact with freight curves with curve radii from 100 to 955 ft and 1-in. super- traffic and are designed with the appropriate "buff load." elevation. The vehicle running speed was 15 mph. The W/R Transit Rail Cars: They normally have two trucks and exam- profile combinations used in the simulations were a 63 flange ples include NYC Transit (subway and elevated); SEPTA wheel for the Type 1 transit rail car and a 75 flange angle wheel (Philadelphia, subway); WMATA; MARTA; Baltimore (sub- for the Type 1 light rail vehicle on standard American Railway way); CTA (Chicago, subway and elevated); Los Angeles; Engineering and Maintenance-of-Way Association (AREMA) MBTA (Boston, subway); and BART. 115 lb/yd rail. The W/R friction coefficient used in the simu- Light Rail Vehicles: They normally have two trucks or three lation was 0.4 to avoid causing flange climb derailments. trucks with articulation. Examples include MBTA (Boston, green line); NJ Transit; Baltimore; Pittsburgh; Charlotte; 3.1 Transit Rail Cars (Type 1) MUNI (San Francisco); Denver; San Diego; San Jose (Valley); Portland; St. Louis; and SEPTA. These cars can be high floor, In most cases, guard rails are installed on the inside of the low low floor, or a combination of both. They are formerly rail. One function of a guard rail is to reduce excessive lateral referred to as street cars or trolley cars. force on the high rail by contacting the low-rail side wheel back. The reduction of lateral force on the high rail is mostly The Type 1 transit rail cars and Type 1 light rail vehicles controlled by the flangeway clearance between the low rail and were used for the steady-state curving simulations in this the guard rail, as the Phase I study (1) of this project showed. section, and all four types of vehicle models were used for the The lateral force distributions between the high rail and the flange climb derailment simulations discussed in Section 4. guard rail are significantly different for these two guard rail All four vehicle models were similar to those used in the TCRP installation philosophies. More than twice the lateral force Phase I guard rail study (1) and the previous TCRP flange climb acts on just the guard rail using Philosophy II, and the lateral

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7 Table 2. Vehicle modeling parameters. Transit Rail Car Light Rail Vehicle Transit Rail Car Light Rail Vehicle Parameters 1 1 2 2 Carbody (Numbers) 1 2 1 3 3 (IRW in middle Truck (Numbers) 2 3 2 truck) Truck Center Spacing 52 23 47.5 24 (ft) Axle Spacing (ft) 7.3 6.3 6.8 6.2 Mid truck: 5.2 Mid truck: 5.9 Wheel Load (kips) 9.45 13.95 End truck: 8.2 End truck: 8.49 Wheel Diameter (in.) 27 27 27 27 Wheel Flange Angle 63 75 63 75 (degrees) force acts almost equally on both rails using Philosophy I installed horizontally on the TTL track, the restraining rail (see Figure 4). The excessive lateral force on the guard rail height was only about 0.5 in. above the low-rail top and resulted will result in rail and component damage and will reduce their in the contact with the wheel on the back of the wheel flange tip. service life. The flangeway clearance optimization methodology Therefore, according to the definition, the TTL horizontally and benefits were investigated in the Phase I report. mounted rail with low height, as Figure 7 shows, was modeled Figure 5 shows that installing the guard rail using Philoso- as a guard rail because its contact angle () on the wheel flange phy II results in a larger rolling resistance than does that of back was less than 90. Philosophy I. Installing the guard rail using Philosophy I with The tests showed that the traction force required to propel optimal flangeway clearance could decrease the rolling resist- the car with the guard rail was about 30% higher than without ance on tight curves with radii less than 250 ft. the restraining rail, as Table 3 shows. The test result was In 1982, a transit rail car was tested on TTCI's Tight Turn consistent with the simulation result in Figure 5, which showed Loop (TTL) (a 150-ft radius curve with 1.5-in. superelevation) about a 10 to 30% traction force increase in the 100 ft and track with and without restraining rails (4). The vehicle weighed 250 ft radii curves as a result of using Philosophy II. 97,020 lbs and had truck center spacing of 54 ft, axle spacing Figure 8 shows that both philosophies resulted in a larger of 7.5 ft, and a wheel radius of 15 in. wear index on leading axle wheels (the sum of the wear index The restraining rail case represents a condition where the from all contact points on both wheels of the lead axle) than wheel flange back contacts the restraining rail at a 90 angle, did the case without a guard rail, but there was a smaller wear as Figure 6 shows. The guard rail case represents a condition index with Philosophy I than with Philosophy II. where the wheel flange tip contacts the rail with a less than 90 The axle steering capability was evaluated by using the axle angle, as Figure 7 shows. Even though the restraining rail was angle of attack (AOA) on curves. Figure 9 shows that the axle Force on High Rail Force on Guard Rail High Rail Contact, No 9000 Guard Rail (a) Type 1 and 2 Transit Rail Cars 8000 Guard Rail Contact, Wheel Lateral Force (lb) Equal Force on Both Rails Philosophy II 7000 High & Guard Rail Contact, 6000 Philosophy I 5000 4000 (b) Type 1 Light Rail Vehicle 3000 2000 1000 0 100 250 320 500 755 955 (c) Type 2 Light Rail Vehicle Curve Radius (ft) Figure 3. Transit vehicles structures Figure 4. The wheel lateral force of a Type 1 transit and layouts. rail car with a guard rail.