- For specific light rail systems, many of which use the words "light rail" as part of their name, see list of light rail transit systems.
urban L-train system (SITEUR
), at first a trolleybus system, opened in 1980
; the second line was opened in 1994, and a third line is in project.
, the diesel light-rail metro service for Ottawa
. It is the first diesel-powered light-rail system in North America.
A Tyne and Wear Metro
train heading for South Shields
calls at Kingston Park station. Although nominally "light rail" the high platforms and full segregation from roads and pedestrians places this system at the upper end of the transport genre which includes street trams.
Light rail or light rail transit (LRT) refers to a form of urban rail transit that utilizes equipment and infrastructure that is typically less massive than that used for rapid transit systems, with modern light rail vehicles usually running along the system.
Light rail is the successor term to streetcar, trolley (both terms used in American English) and tram (used in British English or used to refer to any European or Asian streetcar) in many locales, although the term is most consistently applied to modern or modernised tram or trolley operations employing features more usually associated with metro or subway operations, including exclusive rights-of-way, multiple unit train configuration and signal control of operations.
The term light rail is derived from the British English term light railway long used to distinguish tram operations from steam railway lines, as well as from its usually lighter infrastructure. The term was adopted in the 1970s, particularly in the United States, as a conscious break from the "obsolescent" image of streetcars. It is sometimes used largely for political reasons; in Toronto, Canada the city Transit Commission had to rename a recent project to build a dedicated right of way for one of its streetcar lines as a "new, modern LRT" in order to obtain the support of local elected officials, and then change it back to a "normal, familiar streetcar" to be accepted by the area's residents (the actual project was the same the entire time). However most tramway enthusiats are not plagued by the obsolescent image of "tramcars" and still prefer the term tramway when referring to street based systems with tramway type infrastucture.
Light rail traces its pedigree to street railways, whereas rapid transit (metro) technology evolved from steam commuter operations, such as were seen in London, New York City, and Chicago.
Light rail systems are almost universally operated by electricity delivered through overhead lines, although several systems are powered through different means, such as the JFK Airtrain, which uses a standard third rail for its electrical power, and trams in Bordeaux, France which use a special third-rail configuration in which the rail is only powered while a tram is on top of it (making it safe to install third rails even on city streets). A few unusual systems such as the River LINE in New Jersey (opened in 2004), the O-Train in Ottawa (opened in 2001), and the upcoming SPRINTER in northern San Diego County, California (projected to be opened by late 2007) use diesel-powered trains, though this is sometimes intended as an interim measure until the funds to install electric power become available, or as a compromise with communities strongly opposed to an electrical light rail system because of alleged health fears with the overhead wires.
Attempting to define "light rail"
Most rail technologies, including high-speed, freight, commuter/regional, and metro/subway are considered to be "heavy rail" in comparison. A few systems such as people movers and personal rapid transit could be considered as even "lighter," at least in terms of how many passengers are moved per vehicle and the speed at which they travel. Monorails are also considered to be a separate technology. Light rail systems can handle steeper inclines than heavy rail, and curves sharp enough to fit within street intersections (though this is hardly true for all light-rail lines). They are typically built in urban areas, providing frequent service with small, light trains or single cars.
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, and it is common to classify streetcars/trams as a subtype of light rail rather than as a distinct type of transportation. The two general versions are:
- The traditional type, where the 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 their own right-of-way and are often 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 seperation with non-level crossings. At the highest degree of separation, it can be difficult to draw the line between light rail and metros, as in the case of London's Docklands Light Railway or Wuppertal's Schwebebahn hanging rail system, which would likely not be considered "light" were it not for the contrast between it and the London Underground. Increasingly, light rail is being used to describe any rapid transit system with a fairly lower frequency compared to heavier mass rapid systems such as the London Underground or the Mass Rapid Transit (Singapore).
Many light rail systems — even fairly old ones — have a combination of the two, with both on road and off-road sections. In some countries (esp. in Europe), only the latter is described as light rail. In those places, trams running on mixed right of way are not regarded as light rail, but considered distinctly as streetcars or trams. However, the requirement for saying that a rail line is "separated" can be quite minimal — sometimes just with concrete "buttons" to discourage automobile drivers from getting onto the tracks.
There is a significant difference in cost between these different classes of light rail transit. The traditional style is often less expensive by a factor of two or more. Despite the increased cost, the more modern variation (which can be considered as "heavier" than old streetcar systems, even though it is called "light rail") is the dominant form of urban rail development in the United States. The Federal Transit Administration helps to fund many projects, but as of 2004, the rules to determine which projects will be funded are biased against the simpler streetcar systems (partly because the vehicles tend to be somewhat slower). Some cities in the U.S. (e.g. San Pedro, California) have set about building the less expensive streetcar lines themselves or with only minimal federal support. Most of these lines have been "vintage" or "heritage" railways, using refurbished or replica streetcars harkening back to the first half of the 20th century. However, a few, such as the Portland Streetcar, use modern vehicles. There is a growing desire to push the Federal Transit Administration to help fund these startup lines as well.
Light rail is generally powered by electricity, usually by means of overhead wires, but sometimes by a live rail, also called third rail (a high voltage bar alongside the track), requiring safety measures and warnings to the public not to touch it. In some cases, particularly when initial funds are limited, diesel-powered versions have been used, but it is not a preferred option. Some systems, such as the AirTrain JFK in New York City, are automatic, dispensing with the need for a driver; however, such systems are not what is generally thought of as light rail. Automatic operation is more common in smaller "people mover" systems than in light rail systems, where the possibility of grade crossings and street running make driverless operation of the latter inappropriate for safety/security reasons. However this is obviously not true in completely separated light rail systems such as the Kelana Jaya Line in Kuala Lumpur, Malaysia.
From the mid-19th century onwards, horse-drawn trams (or horsecars) were used in many cities around the world. In the late 1880s electrically-powered street railways became technically feasible following the invention of a trolley system of collecting current by American inventor Frank J. Sprague who installed the first successful system at Richmond, Virginia. They became popular because roads were then poorly-surfaced, and before the invention of the internal combustion engine and the advent of motor-buses, they were the only practical means of public transport around cities.
The light rail systems constructed in the 19th and early 20th centuries typically only ran in single-car setups. Some rail lines experimented with multiple unit configurations, where streetcars were joined together to make short trains, but this did not become common until later. When lines were built over longer distances (typically with a single track) before good roads were common, they were generally called interurban streetcars in North America or radial railways in Ontario.
In North America, many of these original light-rail systems were decommissioned in the 1950s and onward as the popularity of the automobile increased. Although some traditional trolley or tram systems still exist to this day, the term "light rail" has come to mean a different type of rail system. Beginning in the 1980s, some cities began reintroducing light-rail systems that are more like subway or metro systems that operate at street level. These light-rail systems include modern, multi-car trains that can only be accessed at stations that are spaced anywhere from a couple blocks to a mile or more apart. Some of these systems operate within roadways alongside automobile traffic, and others operate on their own separate right-of-way.
As with other rail systems, the rail gauge has had considerable variations, but today standard gauge is dominant. Narrow gauge was common in many earlier systems, although as systems merged or died out, old lines were often upgraded, removed, or replaced. Some systems still use other track gauges, however.
Advantages of light rail
Light rail systems are generally cheaper to build than heavy rail, since the infrastructure does not need to be as substantial, and tunnels are generally not required as is the case with most metro systems. Moreover, the ability to handle sharp curves and steep gradients can reduce the amount of work required.
Traditional streetcar systems as well as newer light rail systems are used in many cities around the world because they typically can carry a larger number of people than any bus-based public transport system. They are also cleaner, quieter, more comfortable, and in many cases faster than buses. In addition, light rail has none of the negative connotations of being a system used by the "transit dependent" that can plague BRT ridership levels. The presence of rail lines demonstrates a long-term commitment by government to a particular neighborhood.
In an emergency, light rail trains are also easier to evacuate than monorail or elevated rapid rail trains.
Many modern light rail projects re-use parts of old rail networks, such as abandoned industrial rail lines.
A good example of both points above is the Docklands Light Railway (DLR) in London, which uses a sharp, steep, curve to enable it to transfer from running alongside an existing railway line to a disused railway line which crossed underneath the first line. A direct connection between these lines would not be practical for conventional rail (note that because the DLR has a completely grade-separated right of way, it can also be regarded as a metro).
Disadvantages of light rail
Like all modes of rail transport, light rail tends to be safest when operating in dedicated right-of-way with complete grade separations. However, grade separations are not always financially or physically feasible.
Monorail advocates like to point out (as a way to disparage light rail and promote monorail) that light rail trolleys are heavier per pound of cargo carried than heavy rail cars or monorail cars, because they must be designed to survive collisions with automobiles.
Criticisms of light rail, and responses to them
In many cases there has been considerable opposition to new light rail systems, particularly in the United States. Arguments are generally along three lines: first, that modern spatial arrangements are unsuited for fixed-line transit systems such as light rail; second, that light rail is too slow to compete with the automobile; and three, that light rail does not generate a sufficient return on capital investment to make its construction worthwhile. Driving Forces (1998), by American political scientist and transit opponent James Dunn, provides a good summary of these arguments.
Light rail opponents argue that modern metropolitan areas are far too dispersed in residential and employment locations for any mass transit facility to be able to remove a significant percentage of drivers from automobiles. In the United States, only in metropolitan New York City is transit's share of vehicle-miles traveled (VMT) higher than five percent, and in most metropolitan areas, transit carries less than one percent of travel. These percentages are considerably higher for suburb-to-central business district (CBD) commutes, but these trips have dramatically declined as a percentage of VMT since the 1970s.
While the spatial mismatch argument is largely correct for the Midwest (excepting Chicagoland) and the South and Southwest, it is increasingly not the case in places such as Los Angeles and San Diego. As West Coast cities, in particular, run into their coastal mountain ranges, many have developed polycentric spatial arrangements with a relatively small number of nodes. For most of its history, transit has best served commuters from suburbs to a single CBD. However, this is no longer necessarily the case; in Sacramento and San Diego, particularly, construction of light rail networks that incorporate both circumferential (suburb-to-suburb) and radial (suburb-to-CBD) lines have produced surprisingly high increases in passenger-miles (Thompson and Matoff, 2003).
Nevertheless, with such a small market share, even a doubling of transit ridership would have virtually no impact on traffic congestion. Smart growth advocates acknowledge this and call for areas near proposed light rail stations to be developed as relatively high-density "transit villages," minimizing the need for automobile usage while increasing the housing stock. (This is a principal tactic used by New Urbanists.) In many areas, NIMBYism is an obstacle to such development, but is expected to fade as automobile congestion continues to erode quality of life.
Opponents also point to the fact that light rail has a perceived disadvantage in travel time. On average, during peak travel periods, light rail operates only slightly faster than buses and barely one-half as fast as automobiles. These averaged figures do not account for the degree of congestion, however; light rail on its own right-of-way is considerably less vulnerable to gridlock than automobiles or buses operating in mixed traffic. For example, Los Angeles' heavily ridden Blue Line (the United States' busiest light rail line, with over 70,000 daily passenger boardings) is much slower than automobiles at off-peak times, but is very competitive with automobiles along the horrifyingly-congested Long Beach Freeway (I-710) nearby. (The Harbor Freeway busway nearby is faster than either mode, but construction of its dedicated right-of-way was extremely expensive given its very low ridership.) It is clear, though, that light rail only makes sense in areas that suffer from sufficient congestion to make it competitive with cars, and along routes that are too heavily traveled for even bus rapid transit systems.
Return on Investment and Cost-Competitiveness for LRT vs. Highway
More generally, as the "face" of mass transit investment in the past two decades, light rail has been the target of arguments that mass transit investment is not a good use of public funds.
- Critics accuse light rail projects of being corruption-prone "money trains," providing wasteful quantities of public money to politically-connected construction firms. Supporters note that other forms of transit (such as highway) are no more immune to the tendency to engage in gratuitous cost overruns and outright graft, as is evidenced by The Big Dig highway project in Boston.
- While not as high as all-new subway construction, LRT still often has a high per-mile cost (especially in areas where transit agencies have to acquire right-of-way by means of eminent domain). Rail proponents respond that highway systems require considerable expenditure out of general funds on pollution control measures, as well as greater numbers of schools and other expensive infrastructure. Additionally, much of the cost of a highway is hidden as a result of the cost of purchasing and maintaining vehicles being assumed by private owners.
- It has also been argued that light rail offers indirect benefits to a metropolitan areas since it is low-impact with regards to hard-to-measure quality of life variables (except noise--q.v.), whereas highway construction has historically wreaked havoc on the social capital of neighborhoods where it occurs and leads to cases of alleged cancer clusters and noise pollution in areas directly adjacent to even moderately-traveled routes.
- Critics also point to low ridership and poor utility to the bulk of the population. LRT supporters argue that many of such criticisms are derived from studies in areas where rail is still under construction or was never completed. This ignores the so-called network effect, whereby the addition of one node to a network increases the utility of all other nodes. The experiences of Sacramento, California and Portland, Oregon have demonstrated this phenomenon to great effect: in those places, light rail became reasonably competitive with highways once a reasonable percentage of the complete network had been put in place. In these and other LRT-heavy cities, greater government sophistication regarding LRT construction has led to a "learning by doing" effect that substantially lowers per-mile construction costs.
- While it can be argued that the postmodern American city does not possess sufficient population density to support mass transit, the geographic reach of the modern public transit system is supplemented by those using cars to get to transit stations.
- Additionally, since highways become terribly inefficient once a certain mass of cars is on the road (e.g. rush hour), it has been argued that mass transit systems such as light rail improve the efficiency and cost-effectiveness of existing highway infrastructure by lowering traffic congestion in much the same way as a carpool program.
However, investment in LRT systems may be stifled on account of the fact that the political atmosphere is not conducive to projects with large up-front capital expenditures. Moreover, existing arterials and freeways are considered sunk costs (despite the enormous expense of road maintenance). Because of this, political bodies are often skeptical of allocating funds to establish a new travel system, instead choosing to incrementally increase road expenditures via widening. Light rail supporters decry this ideology, pointing to the social costs of continued highway dependence, arguing that such actions are examples known in the behavioral economics literature as "improving one's self to death."
Trams operating on mainline railways
Around Karlsruhe, Kassel and Saarbrücken in Germany, Bombardier Flexity Link trams partly use heavy-rail tracks, sharing these tracks with heavy-rail trains. In the Netherlands this was first applied on the RijnGouweLijn. This allows commuters to ride directly into the city centre, rather than having to take a mainline train as far as a central station and then change to a tram. In France similar tram-trains will be realised in Paris, Mulhouse and Strasbourg, further projects exist.
Some of the issues involved in such schemes are:
- compatibility of the safety systems
- power supply of the track in relation to the power used by the vehicles (frequently different voltages, rarely third rail vs overhead wires)
- width of the vehicles in relation to the position of the platforms
- height of the platforms
There is history of what would now be considered light-rail vehicles operating on heavy-rail rapid transit tracks in the U.S., especially in the case of interurban streetcars. Notable examples are Lehigh Valley Transit trains running on the Philadelphia and Western Railroad high-speed third rail line (now the Norristown High Speed Line). Such arrangements are almost impossible now, due to the Federal Railroad Administration refusing to allow non-FRA compliant railcars (i.e. subway and light rail vehicles) to run on the same tracks at the same times as compliant railcars, which includes locomotives and standard railroad passenger and freight equipment. A notable exception is the New Jersey Transit River LINE from Camden, New Jersey to Trenton, New Jersey, which has received an exemption on the provision that light rail operate only during the daytime hours and Conrail freight only at night, with several hours separating one operation from the other.
Third-rail power for trams
- Main article: Ground level power supply
In the French city of Bordeaux, Citadis trams are powered by a third rail in the city center, where the tracks are not always segregated from pedestrians and cars. Safety is ensured by placing the third rail (actually two closely spaced rails) in the middle of the track, and dividing it into eight-metre sections, each of which is only powered while it is completely covered by a tram. There is therefore no risk of a person or animal coming into contact with a live rail. In outer areas, the trams switch to conventional overhead wires.
This third rail technology is being investigated for use on the Gold Coast of Australia in the Gold Coast Light Rail Feasibility Study. See the present draft report here.
Links to sites advocating light rail
Links to sites opposing light rail
Note: the following links are from organizations that oppose light rail out of ideological reasons.