Transportation Deployment Casebook/Life cycle of US LRT


Light rail is a rail transit mode that has predominantly dedicated rights of way. The design is differentiated from heavy rail largely by the use of overhead catenary systems for supplying power instead of a third rail. Diesel may also be used to power light rail. Most light rails operate in consists of multiple cars, each car being capable of operation in either a multiple car consist or individually. The right of way of a light rail system can run at grade, with level crossings and portions can be shared with regular traffic in street conditions. The advantages of this mode over heavy rail is the lower cost associated with the initial capital investments, and greater flexibility in routing; due to shorter train and the ability to run at grade without severe safety hazards, such as a third rail, being exposed to the general public. Advantages over bus service are increased capacity, speeds, energy efficiency and lower operating wages as one driver can operate a train of multiple cars1. One of the largest advantages that light rail had over its competitors was also that it was new, and had not yet been stigmatized as buses and some heavy rail systems had been2. Even in 1975 it was known that “…these features, attract passengers that other surface transit cannot”3, this advantage has been one of the main selling points for years with light rail and has influenced policy on the issue to today.

Qualitative AnalysisEdit


Main markets for light rail are currently in full exploitation in the US, as routes with enough ridership to justify heavy rail have already been built and capacity/image issues with bus service are keeping transit ridership lower than is seen with light rail systems. This is leading to light rail being the backbone of transit systems in medium cities and a feeder system to heavy rail in larger, more developed cities.

Birthing PhaseEdit

Internationally, light rail developed as an improvement in all surface railways. London upgraded many of its overground lines to light rail and built the Docklands line in the 1980s. Other Western European cities upgraded their trams to light rail like systems found in Boston, but instead of main lines, the entire network was converted. Moscow and other eastern bloc cities had extensive light rail routes, Leningrad alone had over 350 miles of route by mid 1980s ; approximately the same amount as the entire US! Asian countries had also used light rail to accentuate metro systems, these widespread applications in other countries showed that a quality light rail system could serve a medium city’s transportation needs very well, and provided a more expansive data of systems for the US to learn from for projects that were constructed in the late 1980’s and beyond.

The term light rail was formally introduced to the United States in 1972 by the Urban Mass Transit Administration. Although the birth of light rail is hard to determine as light rail was not simply invented but instead started as a growth and improvement of streetcar and interurban systems . Buses were the dominant local service for transit and express services in large cities were provided by heavy rail subways, streetcars and interurban lines continued in a select few cities and evolved into light rail themselves, but light rail systems have been predominantly new constructions. The limitations of heavy rail were that it could only operate in entirely separated right of way, due to the danger of the electrified third rail that was used to supply the electricity for the system; this made the systems extremely expensive and very high ridership was needed to justify the investment. Buses were the other mode that help a large portion of the market share for transit, buses had downsides as well; largely these were capacity and images issues, as well as a lack of dedicated rights of way. The personal automobile was the most common form of transportation when light rail was introduced, and cities that had developed mostly in the 20th century, such as Los Angeles, were very reliant on the automobile for their regions’ transportation needs. This dominance and reliance on personal automobiles led to widespread congestion and pollution. The congestion of cities resulted in a need for a more efficient way to move people around, and the forms of transit in deployment at the time were seen as either insufficient or prohibitively expensive.

The technology was not an invention as much as an application of ideas and evolution of systems and thinking. By combining streetcars with running ways that were separated from other traffic to produce systems that acted more like heavy rail than like the streetcars themselves. The initial designs were simple upgrades of streetcar systems already in place, these streetcars systems bought new light rail vehicles and ran them along the previous sections of track. As new systems were built, mixed rights of way were reduced, and planners were able to maximize the benefits of the technology. The two most common changes this led to were low floor car designs, and stations that could accommodate longer trains. Recently there has also been the development of light metro systems, where a subway or other fully exclusive right of way rail system is built using light rail technologies. This is not a new idea as APTA’s 1987 booklet on light rail trumpets that it is adaptable to be upgraded to heavy rail if needed . The light metros are beyond the scope of this section of the paper as they are scarcely deployed in North America and none are in use in the United States.

Growth Brings Changes and Lock-insEdit

The first light rail system built in the US was the San Diego Trolley. San Diego needed to improve its transportation system and decided that using freight rail right of way as corridors for light rail would satisfy the regions needs at a reasonable cost. The success of the line and eventual system in San Diego led to light rail being viewed as a legitimate transportation option for cities that were in need of increasing their transit networks. The success prompted other cities to follow San Diego in creating new light rail lines. Newer systems were built with the Americans with Disabilities Act in a more obvious role; San Diego’s trolleys were originally equipped like buses, with platforms that were at track level and a single wheelchair lift on each car. However new systems feature level boarding and older systems, like San Diego’s, are renovating their stations and rolling stock by raising platforms and adding ramps to vehicle doors instead of using lifts, bringing them into greater ADA compliance, and accelerated boarding for those with disabilities. Commonalities that have continued throughout the development of light rail as a transit mode have been the usage of freight rail or highway rights of way, allowing the rails to be built predominantly at grade.

The ‘legacy’ light rails, primarily upgraded vehicles from PCC cars to LRVs. This increased capacity and running speeds. As the systems transitioned to light rail they also underwent another transformation, like early light rail systems, in installing features to allow for people with disabilities to access the entirety of the system. This has and is currently taking place through the installation of raised platforms and the use of trains with low floor designs to allow for level boarding, and thus better accessibility, along the entirety of the route.

Initially the market for light rail was in upgrading old systems to have more capacity, faster running speeds and replacing PCC cars that had been the predominant choice of light train transit in these areas. Once San Diego built a new system it became clear that this was not just an upgrade for older systems, but could also be used to solve transportation problems that cities had to deal with at the time. This led to cities that had little to no remaining rail transit building new light rail to deal with transportation issues, and increase transit ridership.

The initial market of enhancing existing services plays a relatively small role in the life cycle of light rail. The transit agencies that have ‘legacy’ light rail systems are few, Boston, San Francisco, Newark, New Orleans, Pittsburgh, Philadelphia and Cleveland, and all of these systems were upgraded to meet at least some classification of light rail (New Orleans has some exclusive right of way but uses historic streetcars and replicas). The explosive growth in light rail systems came from new lines being built in places where rail transit had earlier ceased to exist. The lines built to capture markets that previously did not have rail transit now make up the vast majority of systems in the United States.

It is difficult to assign a birthing phase to light rail as when the early systems were transitioned from streetcar service to light rail service is somewhat ambiguous. The idea of light rail did bring a few permanent ideas that were required for all systems, a few “locked in” characteristics. Main characteristics that have been locked in that are not entirely required are that boarding must be allowed through multiple doors, and proof of payment is the fare collection system. These design features have been in effect since the beginning of our data collection and the definition of light rail being sponsored by the Urban Mass Transit Administration. Another characteristic that was seen coming to dominance, although with some dissenters still today, would be the usage of light rail cars with four doors on each side of the vehicle, San Diego’s original vehicles can be seen with four doors on each side . This has become the standard for typical light rail vehicles, again there are some systems which do not comply, such as Boston, but in general light rail vehicle’s eight doors was a design that has been constant since the birth of the mode.

An original design for most light rail systems was the usage of high floor vehicle designs. This design was starting to become locked in when the Americans with Disabilities Act passed and required that all light rail systems be able to provide level boarding to those who would be unable to utilize stairs. Early light rail vehicles had high floor designs and because early light rail systems were meant to be cost effective, often stations did not have raised platforms, using lifts to help persons who could not use stairs. However, to gain compliance with ADA, most transit agencies, upon new orderings for light rail cars, low floor cars were bought, such that stations would only need to be raised a foot or less. This also played into the design of tracks, early tracks were placed and started to look as if some of them were going to be narrow gauge. This was mostly due to the tighter turning radius provided by narrow gauge vehicles. This advantage was negated by the advent of articulated designs, now standard for all light rail systems. Also pushing for standard gauge was the ADA and the new low floor designs, standard gauge was adopted such that wheelchairs could move between the wheels on the center trucks, which is something there was not enough space to do on narrow gauge tracks.

Mother logic for light rail was provided by most other railway operations, and technologically the light rail was very similar to heavy rail and streetcars. Prepayment, multi-door boarding, reserved right of way, formation of consists, and station infrastructure were all taken more directly from heavy rail systems, while mixed right of way and vehicle design closely follow that of streetcars. The proof of payment concept was borrowed from former rail modes as well. Which mode was the origin of this mother logic is unclear, whether commuter rail, long distance rail, or streetcars. All these modes have, at one time, used some sort of proof of payment mechanism to collect fares.


“Light Rail is cool, it’s sexy” —Kathleen Gaylord, Dakota County Board Chairwoman.

People like trains. Trains are seen differently than other modes of transit, especially light rail trains. When Ms. Gaylord said those words she was referring to a bus rapid transit line that was built in lieu of light rail in a corridor. While explaining that light rail in that corridor would have been prohibitively expensive and that the ridership was not there , Ms. Gaylord gave what may be the most honest opinion of both the general public and planners alike for many years. Private sector developers have built large transit oriented developments around light rail. With Minneapolis-Saint Paul being a prime example, more than $1.7 Billion worth of construction has taken place along the Green Line/Central Corridor, more than half a year before the line is actually in service . While development can be spurred by other medium and high volume transit projects, such as quality bus rapid transit or heavy rail, at the time of construction for most light rail systems heavy rail was too expensive and BRT was just an emerging technology. Development and growth are almost always things that politicians and other policy makers like to talk about and promote, and light rail gave local politicians the ability to say that their neighborhood, city, or even metropolitan area was getting development that it otherwise would not be receiving. These private sector actions influenced the public sectors at local levels to push for more rail transit and to push hard. This political investment in getting rail transit did yield results and was a driving factor in solidifying light rail as the mode of choice for major corridors in mid-size cities.

Light rail is still in its growth phase, but an emerging challenge that is currently developing is the advent of bus rapid transit. Medium capacity transit was formerly the niche that light rail fit and now that there is competition in the niche it is likely that light rail’s share of the market will be lessened. The competition with BRT will force light rail to provide proof of its superiority and cost effectiveness, it will have to cede market share to BRT. If the emergence of BRT as a transit system does gain significant market share in the medium capacity range of transit it will force light rail into a smaller niche. As light rail is refined it will be seen if the mode is outcompeted or if its refinements and those correspondingly done to BRT will create a more efficient transit system overall. This is important because if light rail is outcompeted the latter half of the S-curve documenting its growth will be stunted, whereas if increased efficiency results in light rail surviving growth may slow, but it will complete its S-curve leveling off slowly over a long period of time.

Maturation PossibilitiesEdit

Light rail development has not reached maturity, as can be seen by the attached graphics. The likely inflection points for light rail start in 2006, but there is not enough data currently to identify any year as being an inflection point for the development of light rail. When light rail in its current form does reach maturity a possible expansion and application that is not currently being exploited in North America is the light metro. Light metros are using light rail technology but having the trains being built in nearly to completely exclusive rights of way, essentially where a light rail would be just a smaller subway. Advantages of this application are higher speeds and capacities than normal light rail as cross traffic does not need to be accounted for; however it is far more expensive than normal light rail, the only significant cost savings over heavy rail at this point come from the less expensive, shorter stations. This possible utilization was detailed previously as a reason APTA gives for supporting the building of light rail . Light metros are not unheard of, the light metro concept is how light rail was commonly implemented in the eastern bloc countries, with their extensive systems and high ridership it is clear that this utilization of light rail technology could be used in the United States to a similar effect, becoming a mode for cities to concentrate around.

On the other end of the spectrum, many systems currently use only their own right of way for the entirety of their routes. More mixed use right of way in places where gaining exclusive right of way would be difficult may also be a possible adaptation of this mode. This style of mixing streetcars with light rail is utilized by the San Francisco Muni system, where portions of routes are still the streetcar routes they were initially, but there are segregated and fully separated rights of way along busy portions of the route . This street running would be applicable for more local service and for service to be expanded in crowded areas with minimal investments in eminent domain or removal of traffic lanes. This application of the mode seems less likely, as the mind set of what light rail is has been set as containing their own rights of way. This lock-in is efficient as routes with significant amounts of mixed right of way would not have much better times or reliabilities than buses traveling on the same roadways. This usage of light rail will likely be implemented with short, minor segments being constructed and a continuation of service already in effect, but no second growth phase of any considerable size for light rail is likely from this application of the technology.


Data for light rail is hard to come by, very easy to come by; however, the quality of the data is most always in serious question. This paper utilized the National Transit Database and Bureau of Transportation Statistics for directional-route-miles of light rail systems. These statistics only date back to 1985, and have their own inconsistences, but this data was more conducive to analysis and more easily made consistent than the data that was able to be gleaned from other sources. Because the data only dates back to 1985 it is incomplete, some of this time spent means that new systems like San Diego and Buffalo are seen as equal to the upgrades and application of light rail technology to existing streetcar systems. When attempts were made to counter this and back track the technology to the 1970’s data was either missing or was inconsistent, due to expansions and alterations to the networks. If this project had been decided on and started earlier it is likely that a way to account of these would present itself, but due to time constraints placed on this project by bad timing and planning on the writer’s behalf, this was infeasible. Data from 1985 to 1990 was not provided in available data sets. This gap in the data was accounted for using a linear extrapolation; with more work this data could be improved to better reflect the actual building of the systems, but it is likely that an extrapolation between the two numbers would be required, just not relied on as heavily. A final data inconsistency was the National Transit Database’s inclusion of hybrid rail and streetcar sail in their 2011 reports when they had not been accounted for previously. The route miles for hybrid rail were added to the miles for light rail as the glossary of terms for the database declares that “This service typically operates light rail-type vehicles as diesel multiple-unit trains (DMU's).” This also assures that the data is consistent with the qualitative results section above that said light rail was typically electrified but not exclusively.

The data shows that as of yet the United States light rail systems have not had an inflection point, but route kilometers keep increasing at an increasing rate. This means that the table for Excel’s regression is not useful and is not displayed. Data using 5,000 directional-route-kilometers, an approximate doubling of the current system, was used for the first graph. Possible inflection points were seen in the data around the mid 2000’s as growth started to approximate linearization, it could be possible that simply the size of the data set is preventing the observation of an inflection point when one is currently in the data. A second graph is also attached; this graph shows the predicted growth of the system using different years as inflection points. Due to competition with other modes, namely bus rapid transit, it is unlikely that the year of the inflection point for light rail’s route kilometers is so far beyond the latest data set on this graph that it is not useful.

The second graph’s four curves were chosen from their inflection points. The lowest was assuming the inflection point of the mid 2000’s was real, next higher was assuming that 2011 was an inflection point, and the latter two points were for 2015 and 2020 respectively. These points were chosen due to their end values being in general double to triple the current values for total directional route miles, and for their relatively even distribution of years for light rail’s growth to slow.

This graph was produced using the year 2011 as the inflection point for the data, which also gives us this chart. Standard errors and t Stat on this should not be heavily weighted, as I am not very confident in their values.

Regression Statistics
Multiple R 0.986
R Square 0.973
Standard Error 17.778
Observations 27
coefficients Standard Error t Stat
Intercept -160.445 770.148 -0.208
b 0.07977 0.38290 0.208

The predicted values for every year and inflection point, as well as on a graph of every year are as follows;

Using different inflection points for the growth of light rail

From this data it is unclear when light rail will hit its inflection point, or cease its growth. It is clear however, that new systems and extensions will be built for the next twenty or so years as long as the technology maintains its S-Curve.