Transportation I. Transit A. Rail: terms and application

TOD or transit-oriented development is a complex topic that can nevertheless be demystified. In new urbanist parlance, the “transit” of TOD is often assumed to refer to rail. But rail is merely the most glamorous of various means, including buses, circulators, and even taxis, around which TOD land uses may be arranged. The term is better understood as including all sorts of transportation in which the vehicle is held corporately or in common and used for fee. This Technical Page will discuss rail transit components, and other means will receive subsequent discussion. Transit can structure and strengthen an urban fabric, or constrain and even damage it. Its potential virtues are multiple, but the contribution to alleviation of traffic congestion alone means one or more forms of it ought always to be planned for — even if not immediately practicable. Rail transit comes in four magnitudes: heavy, light, streetcar, and trolley. Each has characteristic vehicles, tracks, supporting infrastructure, urban contexts, and sizes of catchment area. The differences are not sharply drawn; each type is capable of some morphological transformation depending upon where it is. Ultimately, the terms light and heavy represent less the actual weight of the equipment than its relative physical effect on the urban fabric. Today’s heavy rail is the descendant of nineteenth-century, central-city-and-outlying-towns systems when it was the only means of fast transportation. It has locomotives and multiple cars, highly engineered trackbeds, and stops at individual towns or garden suburbs with substantial separating distances. Overcoming distance requires speed, and so the trains run on their own rights-of-way, separate from the road network. Abhorring road crossings, they must become grade-separated when they enter city fabric, or else cause circulation problems. Feeders for cities Heavy rail lines are feeders for the core cities of their regions, requiring local and headhouse stations. New York’s Long Island Railroad and the Main Line of Philadelphia are perhaps the most vigorous surviving examples. With the exception of the densest T5 and T6 locations, heavy rail stations must have significant parking — since their catchment is the large surrounding area of passengers who drive to the stations — and provision of ample queuing space for buses and taxis in bigger cities, or dropoff cars in suburbia. Heavy rail usually entails an intermodal change, and that is its weakness; once in their cars, people tend to continue driving to their ultimate destinations — unless there is traffic hell to pay. Heavy rail’s success is highly correlated with intolerable traffic congestion. At first sight, a light rail train appears little different from a heavy rail train, but its engine and braking mechanisms and lighter weight allow it both to accelerate and stop faster and to run on trackbeds within arterial-level rights-of-way. The stops (not necessarily full stations) are spaced as closely as a mile or two. The closer station spacing allows a higher incidence of pedestrian-accessed usage. It is important to be aware that the catchment area — roughly a half-mile radius — and design of community stations consequently are distinct from those of auto-fed commuter stations. At the same time, once outside the more frequent stops of the urban fabric, light rail can function exactly like heavy rail and its planning should proceed accordingly. Even when light rail tracks can be embedded in paving, they are usually fenced to control vehicular and pedestrian crossings. The tracks consequently have a negative effect on the other users of the street system; overall connectivity must be considered in planning TOD. A streetcar system is lighter still, especially in its impact on the urban fabric. Tracks are embedded in the street without further ado, and their space can be shared and crossed. Streetcars, even a pair of flex-connected ones, can be as agile as buses — and quieter. They are common across Europe — the Zurich and Brussels systems are famously entwined in their cities. Streetcars require visual tolerance for overhead electrical wires, and a level of rudimentary intelligence — apparently extinct in most of North America — from the car drivers around them. Streetcars, stopping at half-mile intervals or so, are an inherently neighborhood-friendly technology. A fourth variety of transit, the trolley, deserves to be distinguished from the streetcar. A century ago, American cities possessed a widespread system, now wholly vanished, of very lightweight, surprisingly frequent, rural and intercity trolleys. Single electric cars running silently on negligible trackbeds, they connected and enlivened places, otherwise only served by horse and buggy, to the feeder lines of cities. Circumstances favoring the revival of such systems may well be arising again. u