Light Rail Types

Light Rail Types

Due to varying definitions, it is hard to distinguish between what is called light rail, and other forms of urban and commuter rail. A system described as a light rail in one city may be considered to be a streetcar or tram system in another. Conversely, some lines that are called "light rail" are very similar to rapid transit.

In recent years, new terms such as light metro have been used to describe these medium-capacity systems. Some "light rail" systems, such as Sprinter, bear little similarity to urban rail, and could alternatively be classified as commuter rail or even inter-city rail. In the United States, "light rail" has become a catch-all term to describe a wide variety of passenger rail systems.

There is a significant difference in cost between these different classes of light rail transit. Tram-like systems are often less expensive than metro-like systems by a factor of two or more.

Light Rail Lower Capacity

The most difficult distinction to draw is that between light rail and streetcar or tram systems. There is a significant amount of overlap between the technologies, many of the same vehicles can be used for either, and it is common to classify streetcars or trams as a subcategory of light rail rather than as a distinct type of transportation. The two general versions are:

The traditional type, where tracks and trains run along the streets and share space with road traffic. Stops tend to be very frequent, but little effort is made to set up special stations. Because space is shared, the tracks are usually visually unobtrusive.
A more modern variation, where the trains tend to run along with their own right-of-way, separated from road traffic.

Stops are generally less frequent, and the vehicles are often boarded from a platform. Tracks are highly visible, and in some cases, significant effort is expended to keep traffic away through the use of special signaling, level crossings with gate arms, or even a complete separation (semi-metro) with non-level crossings.

Light Rail Higher Capacity

At the highest degree of separation, it can be difficult to draw the line between light rail and metros. The London Docklands Light Railway would likely not be considered as "light rail" were it not for the contrast between it and the rapid transit London Underground. In Europe and Asia, the term light rail is increasingly used to describe any rapid transit system with a fairly low frequency or short trains compared to heavier mass rapid systems such as the London Underground or Singapore's Mass Rapid Transit.

However, upon closer inspection, these systems are better classified as light metro or people movers. For instance, Line 1 and Line 3 in Manila are often referred to as "light rail", despite being fully segregated, mostly elevated railways. This phenomenon is quite common in East Asian cities, where elevated metro lines in Shanghai, Wuhan, and Dalian in China, and Jakarta, Greater Jakarta and Palembang in Indonesia are called light rail lines. In North America, such systems are not usually considered light rail.

Light Rail Mixed Systems

Many systems have mixed characteristics. Indeed, with proper engineering, a rail line could run along a street, then go underground, and then run along an elevated viaduct. For example, the Los Angeles Metro Rail's L Line "light rail" has sections that could alternatively be described as a tramway, a light metro, and, in a narrow sense, rapid transit.

This is especially common in the United States, where there is not a popularly perceived distinction between these different types of urban rail systems. The development of technology for low-floor and catenary-free trams facilitates the construction of such mixed systems with only short and shallow underground sections below critical intersections as the required clearance height can be reduced significantly compared to conventional light rail vehicles.

It is even possible to have high-floor rapid transit cars run along a street, like a tram, this is known as street running.