Years ago, General Motors tried to counter the perception that one of its brands — with an unfortunate name — was old-fashioned with the campaign, "It's not your father's Oldsmobile." Though that brand was ultimately phased out, much the same can be said of today's rail transit vehicles. While their exterior appearance is similar, inside, they are vastly different products.

And rail transit vehicles are in no danger of going away. The rail transit sector is undergoing a growth spurt in North America, held back only by limits in the amounts of available funds. In the United States, the Federal Transit Administration gets about ten times the number of requests for matching financing for rail transit than it can fill, leading to both long wait times and complex qualification procedures.

Externally, the whole range of rail vehicles used in various transit applications has changed little over the years, and stylistic variations depend mostly on the specific manufacturer; internally, the picture is quite different. Nowhere is this more pronounced than with electric light rail, the fastest growing sector of rail transit.

The delineations between light rail, heavy rail (usually referring to subway systems) and commuter rail are not absolute, and some new transit systems exhibit characteristics associated with more than one mode. But, if you define light rail as the successor to the streetcar and trolley of old, the technology differences are startling.

Though many American systems still have sections of street running (tracks embedded in the pavement and the right of way shared with road vehicles) in downtown areas, most of their routes are now on their own rights of way, with welded rail on concrete ties and with signals controlled from a central dispatching center.

Onboard Computers

Internally, complex relays have given way to solid state devices, and most of the operations of the vehicle are now managed with the assistance of one or more onboard computers. The shrinking size of the electrical components, once taking up much of the space under the car, has enabled the development of low-floor vehicles.

Typically, these vehicles have about 70 percent of their interior floor level only a few inches above track or street level. The floor still has to be higher in the areas above the wheels.