2017 Rail Transit Session
Re-Engineering Wheel / Rail Interaction on LA Metro: Learning from Experience
This presentation will provide a summary of what occurred and why these rail system engineering activities were necessary. In the mid 1990’s , LA Metro was opening a new Underground Rail Transit System that was consistent with many other rail transit system around the world. However, the designers of the Heavy Rail Vehicles and the Heavy Rail Underground Alignment had different objectives to satisfy their specific goals. The Vehicle Manufacturers where specified to design a high speed rail transit vehicle that could operate at 75 mph through an underground alignment that originally was relatively straight with only non-revenue tight curves leading into and out of the heavy rail yard. The underground alignment however, was specified to operate up to 75 mph but would allow minimum of 500 foot radius curves and #10 Turnouts for mainline track design. The Vehicle Manufacturers reviewing the initial alignment decided to go with commuter type proven trucks with large 34.5 inch diameter wheels and truck axle spacing of 7 foot 7 inches to ensure high speed stability. The Alignment Designers determined that since it was a rail transit system the cheapest underground alignment was to follow city rights-of-way creating tight radius curves and customize the failure management crossovers to minimize underground excavation. Both groups provided LA Metro with a cost effective rail car and a cost effective underground alignment; but once Rail Transit Operations Department began testing the two separately designed systems together, serious problems arose. The design speeds for #10 Turnout Cross-Over scheduled for 25 mph operation with the large commuter trucks created potential safety risks resulting in cross-over speeds to be lowered. Similarly the tight alignment rail transit curves for vehicle with small wheels and short trucks created excessive wheel and rail wear. The System Components Designed where not designed as a true rail system but LA Metro Rail Operations was forced to solve the mismatch of these rail designs and produce a long term cost effective rail operating system.
To this effort LA Metro Operations together with outside specialists modified the wheels and alignment through system engineering. As indicated in Public News Articles the obvious problems and cost implication to the New LA Metro Rail Transit Operating Departments were documented. However, the articles where selective to vehicle problems or alignment problems but did not really discuss the overall engineer system solution needed to correct the long term operating problems. This presentation will outline the overall engineering solution that resulting in the development of the LA Metro Custom Wheel Profiles for Heavy Rail Transit Wheels and the associated Custom Rail Grinding Templates needed to bring together two problematic designs so that a systematic and comprehensive O&M system can ensure a long-term, safe, reliable, and efficient rail transit service to the LA Area. This presentation should also guide future construction and procurements within the Rail Transit Industry,