Wednesday, April 22, 2020
Saturday, April 4, 2020
Vehicle/Trackway Interface (1 of 2)
As vehicle technology continues to evolve, so does the complexity of the interface between the vehicles and the track. There are few hard and fast rules about the relationships between vehicles and track on light rail transit systems. In spite of this lack of design consistency, there are several key vehicle-to-track and trackway parameters that the track designer must consider during design of light rail systems. These include:
Vehicle Weight (both empty and with full passenger load)
Clearances
Required track-to-platform location tolerances to meet ADA requirements
Required clearance between cars on adjacent tracks considering car dynamics
Required route clearances (wayside, tunnel, bridge) considering car dynamics
Wheel Dimensions
Wheel diameter, which can be very small in the case of low-floor vehicles and is virtually always smaller than that used on freight railroad equipment. Smaller wheel diameters produce higher contact stresses than larger wheel diameters, with resulting implications regarding rail corrugation and wear on both wheels and rail
Wheel profile or contour, including the wheel tread width, which must be compatible with the rail section(s) selected, particularly in the case of special trackwork
Wheel gauge, to ensure compatibility with the track gauge, including tolerances
Wheel back-to-back gauge that is compatible with flangeway dimensions and special trackwork check gauges
Longitudinal Vehicle Forces on the Track
Maximum acceleration and associated tractive forces
Maximum/emergency deceleration from a combination of friction brakes, dynamic braking and electromagnetic track brakes, including the automatic application of sand
Lateral Vehicle Forces on the Track
Maximum lateral forces resulting from all speed and curvature combinations
Dynamic Vehicle Forces on the Track
Impact of car and truck natural frequencies
Impact of wheel flats or damaged wheels