The National Academies

TCRP C-16 [Completed]

Center Truck Performance on Low-Floor Light Rail Vehicles

  Project Data
Funds: $250,000
Research Agency: Interfleet Technology, Inc.
Principal Investigator: Trevor Griffin
Effective Date: 10/19/2004
Completion Date: 4/18/2006

Low-floor light rail vehicles are used by many transit systems with increasing popularity. The typical design includes a three-section articulated vehicle body with the center section connected to a center truck with non-powered, independently rotating wheels. The leading and trailing sections of the vehicle are each supported by a motored truck at one end and by the common non-powered center truck at the other. The low-floor height prevents the use of wheel sets with solid axle connections between right and left wheels of the center truck.

In acceleration and braking modes during curving, because there are two articulations connecting the center section, the center section and truck may rotate excessively causing a high angle-of-attack and flanging. Also, the independently rotating wheels of the center truck do not promote self-steering through the curve, increasing the angle-of-attack and flange forces. This condition leads to increased flange wear, gauge face wear, stick/slip noise, and potential for derailment at curves and special trackwork. Wheel life of the low-floor center truck can be significantly less than that of motored trucks.

Research was needed to better understand the performance of the center trucks of low-floor light rail vehicles, compile lessons learned to date, and provide guidance to transit agencies and light-rail vehicle manufacturers on how to mitigate performance problems.

The objective of this research was to provide guidance to transit agencies and low-floor light rail vehicle manufacturers for the mitigation of problems associated with the design and operation of non-powered center trucks on a three-section, articulated vehicle body with the center section fixed to a center truck with independently rotating wheels.

This research identified contributing factors that can cause events such as derailments, excessive noise, excessive wheel and rail wear, and reduced ride quality (e.g., hunting and excessive curving). The research provides (1) guidance for existing light rail systems, and (2) guidance for future vehicle procurements and track design. The guidance identifies mitigation actions related to vehicle and track (including curved and special trackwork) design specifications, the wheel/rail interface, track construction and maintenance tolerances, and the use of turnout point protection and friction modifiers.

Status: Completed---The revised final report was published as TCRP Report 114

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