By Dale Muellerleile, P.E.

Following years of planning, public debate and several false starts, the United States is poised to implement a comprehensive high-speed rail network connecting major cities throughout multiple regions of the country. A vision has emerged that maximizes the efficiency and capacity of our existing rail network, complements air and automobile travel, unifies the country and promotes safe, energy-efficient and environmentally responsible transportation choices to large portions of the population. Congress and the new administration, through passage of the Passenger Rail Investment and Improvement Act of 2008 (PRIIA), as well as the American Recovery and Reinvestment Act of 2009 (ARRA), have provided the structure to begin implementation of this vision.

Definitions
First, it is necessary to lay out some definitions that can help shape the understanding and debate over where and how high-speed rail may be implemented in the United States. “True” or express high-speed rail, as implemented in Europe and Asia, reaches top speeds in excess of 200 mph. It utilizes electrified trainsets and requires segregated or sealed corridors, with no intermingling of freight trains. To accommodate the high speeds, it must be fully grade-separated (i.e., no at-grade crossings with other modes) and have exclusive right-of-way with fairly restrictive requirements as to curvature and grades. The French TGV service is representative of this type of system, and the proposed California High-Speed Rail network is being planned for these types of speeds.

Regional high-speed rail provides somewhat slower speeds — 110 mph to perhaps 150 mph — and may utilize either electrified or non-electrified trainsets. Segregation from freight operations and a grade-separated corridor are the norm. Through the use of tilt train technology, high speeds can be achieved on right-of-way with sharper curves than designed for express high-speed rail. Amtrak’s Acela service between Washington, D.C., New York and Boston is representative of this classification as are many of the intercity trains operating overseas.

Incremental or emerging high-speed rail includes passenger train speeds up to 110 mph. While passenger rail service at speeds up to 110 mph is not incompatible with freight service within a shared corridor (if not shared track), there remain significant challenges with that approach. Current signal system/equipment, maintenance and regulatory constraints generally limit freight speeds in the United States to 79 mph. While higher passenger train speeds on the same corridor may be possible with limited civil improvements, a shared corridor requires compatibility of the signal systems, meaning that passenger speeds above 79 mph on a freight corridor require upgrading of the freight system as well — a costly, if not insurmountable requirement.

Furthermore, insurance and liability issues, limited capacity for additional trains, limited right-of-way for additional tracks and higher levels of track maintenance are some of the issues causing legitimate concern by the freight carriers regarding when, where and under what operating conditions they might be willing to allow passenger service. While operations up to 110 mph do not require a fully grade-separated corridor, enhanced protection such as four-quadrant gates are required, and crossings should be eliminated whenever possible.

Numerous studies are ongoing for the introduction of incremental or emerging high speed rail throughout the country. Amtrak and the State of Washington currently operate/fund the Cascades service between Vancouver, B.C., Seattle and Portland on a shared corridor (including shared track) with BNSF Railway. While current conditions limit passenger train speeds to 79 mph, capacity improvements are under study now that will allow speeds up to 110 mph in the future.

Technology
Though there are other technologies, such as magnetic levitation (mag-lev), monorail and even more exotic propulsion systems being studied and implemented around the world, the focus of this article is on traditional “steel-wheel-on-steel-rail” technology. The availability of proven technology, as well as an ever-increasing sensitivity to air quality, emissions, noise and other environmental considerations combine to favor, if not require, the choice of electrified trainsets for speeds above 125 mph. At slower speeds, the use of diesel or diesel-electric equipment may allow considerable cost savings related to electrifying an existing corridor. The use of tilt equipment — trains that, through active or passive technology allow the car body to compensate for the effects of lateral forces as a vehicle negotiates a curve — allows higher speeds through existing track curves than conventional equipment. In addition to providing a higher level of comfort and safety on curves, tilt technology can play a critical role in reducing travel times between destinations.