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24 Table 3-1. Summary of measures. Performance problem Derailment Wheel wear Rail wear Noise Ride Vehicle parameters Trailing truck wheelbase Minimal effect Minimal effect Minimal effect No effect No effect (Variations within limited space available on the center truck) Smaller wheel diameter/ Avoidable Increases Increases Increases No effect wheel flange length effect Variation in wheel diameter Minimal effect Minimal effect Minimal effect No effect Minimal effect Wheel parallelism Effects Effects Minimal effect Minimal effect No effect Wheel profile parameters Flange angle Effects Effects Minimal effect Minimal effect No effect Toe radius Effects No effect No effect No effect No effect Flange height Extra safety No effect No effect No effect No effect Tread width Avoidable Minimal effect Minimal effect Minimal effect No effect effect Blend radius Effects No effect No effect No effect No effect Flange thickness Indirect effect No effect No effect No effect No effect Tread radius/taper Effect Effect Effect Effect Effect Other vehicle features Center section fixing to truck Possibly Possibly Possibly No effect No effect minimal effect minimal effect minimal effect Position of secondary suspension Minimal effect No effect No effect No effect No effect Inter-body damping Effect Improves Improves Improves Improves Primary suspension stiffness Effect No effect No effect No effect Effect Use of flange tip running Reduces risk Effect Effect Effect No effect Lubrication Minimal effect Effect Effect Effect No effect Track parameters Gauge tolerances Effect Effect Effect Effect Effect Flangeway clearance Effect Effect Effect Effect No effect Other track features Use of tighter tangent track Effect Effect Effect Effect Effect Sharp curves Possibly Impact Impact Impact Possibly Gauge widening on curves Possibly Impact Impact Impact Possibly Tangent track between curves Possibly Possibly Possibly No effect No effect Use of restraining rail Effect Effect Effect Effect No effect Undercut switches Effect No effect Local effect Local effect Local effect Extra guard rails and house tops Extra safety No effect No effect No effect No effect Embedding rails No effect No effect No effect Effect No effect Flexible switches Effect No effect No effect No effect No effect Switch rail tip design Effect No effect No effect No effect No effect There has also been one derailment in Minneapolis (see sec- or because the loads on the contact area are extremely high. It tion 2.3.6). is also possible for wear to occur as corrugations or for it to propagate more quickly because of wheel flats or localized track irregularities. High points will be eliminated if the 3.2.3 Solutions wheel-rail interfaces match under all conditions. Relative Strategies to manage the wheel-rail interface (e.g., opti- hardness of wheel and rail can be managed so as to keep wear mizing the flange angle in combination with the rail profile in from this cause within acceptable limits. Certain conditions use) are essential to preventing flange climbing derailment. In can increase contact area loads, including sharp curves. It addition it is necessary to manage other features of the vehi- is possible to reduce the conditions that create rail corruga- cle that might increase the angle of attack. The wheel-rail tions and wheel flats and to eliminate the track irregularities interface is also the key to preventing track discontinuity that cause most wear. The LFLRVs considered in this study derailments, but here the prevention of track discontinuity is may be more susceptible to wear because IRWs and the cen- clearly also critical. ter truck configuration make it more difficult to manage the relative aspects of the wheel and rail at the interface. 3.3 Excessive Wheel and Rail Wear 3.3.2 Experience with Excessive Wheel 3.3.1 Basic Causes and Rail Wear For any type of LRV, wear will occur because localized high Excessive wheel and rail wear is a major issue for many light points on the wheel or rail profiles cause high contact stresses, rail systems, and many new systems worldwide seem to have because the rail is softer than the wheel material or vice versa, experienced this, regardless of the type of vehicles used.