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|
Mode |
Rolling stock |
Right of Way |
Operating Patterns |
| Light Rail Successor to the streetcar, though some systems may not have any on-street operation. Equipment is much more technologically sophisticated than early streetcars. |
Relatively short, sometimes
articulated self-propelled cars—normally
electrically powered—sometimes hauling unpowered
trailers. Modern light cars can typically operate in
multiple, controlled by a single operator. Maximum train length is affected by size of city blocks to avoid having stopped trains block intersections. Multiple large doors for fast loading and unloading are common. |
May include any of the following:
Boarding platforms are typically low, though some systems with no street running have high platforms. |
Operates with high frequency in
built-up urban areas. Operator controls most of the movement of the train, though some junctions or busy sections may have signaling. A few systems with no street running in mixed traffic are highly automated with manual operation only in emergencies for terminal shunting. Generally not compatible with freight operations on the same tracks for safety reasons.1 |
| Heavy (or Transit) Rail2 Includes most subway systems. Overlaps with commuter rail in many attributes. |
Typically low profile to minimize
expense of tunnel construction. Cars are relatively short for operation on tight radius curves. Equipment sometimes consists of married-par cars which share equipment and are incapable of operating independently. Multiple large doors for fast loading and unloading are common. |
Typically operates extensively in
tunnels or on elevated rights of way, particularly in
built-up urban areas. Minimum curve radii are larger than for light rail but tighter than those found on commuter rail lines. Boarding is typically from high platforms even with the floor level of the rolling stock. |
Does not mix with freight traffic for
technical rather than safety reasons: Tight radii and low
tunnel clearances make lines unsuitable for freight cars. Operates at set intervals with higher frequencies during rush hours. Entire line has signaling controlled from main dispatch center. Signaling is fairly basic. |
| Commuter Rail2 Suburb to city and city to suburb directional service on existing rail corridors. |
Trains can be both locomotive-hauled
(often in push-pull mode with a cab control car on one
end) or multiple-unit self-propelled, with either
electric or diesel propulsion. Because of relatively short travel times, seating density is typically high. In some areas, double-decker cars may be used. Large doors for fast loading and unloading are common. |
Typically operates on a host
(freight) railroad's tracks, though in some cases, the
host railroad may be an intercity railroad, or the
commuter rail operator may own the right of way. Though the host railroad will try to schedule operations around commuter trains, freight train interference is possible. |
Typically operates in existing
freight and intercity rail corridors and may share tracks
with both of these types of operations. Operates primarily during morning and evening rush hours with directional service (more trains inbound in morning; more trains outbound in evening). Density of traffic typically mandates signaling, at least for the lines the core urban areas. |
| Intercity Rail2 The traditional long-distance passenger train. Trains on longer routes may offer special amenities, such as food service and sleeping cars. |
Typically locomotive-hauled, with
single or bilevel rolling stock, depending on clearances
on the lines traveled. Special-purpose cars in addition to coaches may include sleepers and diners, as well as ones for baggage and express goods. Seating in coaches is less dense than on commuter stock to provide additional comfort on longer trips. |
These trains may travel on a variety
of routes with variety of track. In North America, the intercity rail operator is usually dependant on a host railroad for the right of way on which the trains operate. |
Though some allowances may be made
for convenient departure or arrival in end-point cities,
schedules are not dependant on time of day. Busy corridors may have trains operating at set intervals, such as hourly. Trains on some routes may add or drop cars at intermediate points. |
| High Speed Rail2 Dedicated equipment capable of operating at 150 mph or higher. |
In addition to having special
suspension for running at high speeds, rolling stock is
largely pressurized, with air-tight doors and connections
between cars. Amenities are similar to intercity rail. |
This equipment, while designed for purpose-built high-speed lines, may also be found operating—at lower speeds—on conventional and upgraded older rights of way, particularly in urban areas where new rights of way would be too expensive. | Signaling is typically continuous through an antenna cable mounted between the rails, with trains operating at high frequencies to take maximum advantage of the investment in equipment and infrastructure. |
By Ernest H. Robl
When you read or hear passenger railroad operations described as "light rail," "heavy rail," or "commuter rail," keep in mind that these are descriptions of general concepts that have no absolute deliniations.
Each term provides a shorthand of defining operation with general characteristics, though the details may vary from instance to instance. These characteristics apply to three general areas:
In addition to the three concepts mentioned in the first paragraph, let's also look at two additional forms of rail passenger transport:
The table on the reverse of this page is an attempt to explain both differences and similarities of the modes.
"You can't tell which way the train went by looking at the tracks," run an old adage. Because all of these modes, from one extreme to the other, have more in common than they have differences, you also cannot determine the type of railroad operation by looking at a section of track.
Doors and the related interior configuration of the railcars provide a good means of identifying the purpose for which they were built:
Light Rail:
San Diego Trolley; Baltimore Light Rail
Heavy (Transit) Rail:
Metro (Washington, D.C.); BART (San Francisco Bay area)
Commuter Rail:
Virginia Railway Express; Metra (Chicago)
Intercity Rail
Amtrak (USA); VIA (Canada)
High Speed Rail
Northeast Corridor (Amtrak), though this only minimally qualifies as high-speed rail by international standards.
| This document, including the table at the top, is Copyright © 1999-2003 Ernest H. Robl, all rights reserved. It is provided for your personal use. Reproduction or inclusion of this material in another work without written permission of Ernest H. Robl is prohibited. |
[rev. 2003/05/08]
Ernest H. Robl, Durham, NC, USA +1
(919) 401-9480; fax +1 (919) 402-0721
ehr@mindspring.com
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