Transportation Deployment Casebook/2015/US Light Rail Development

Light Rail Development in the United StatesEdit


Light rail in the United States has progressed significantly since the early 1970s. This form of transit is the successor to the American street cars of the early twentieth century which once dominated the urban landscape. Light rail built off of the street car model by using existing infrastructure and supporting technology. New light rail development takes after the street car lines of days past because many of these corridors shaped the existing U.S. cities and make logical sense for placing new transit systems. Since 1980, over 25 light rail systems have opened in the United States. Light rail continues to be the most favorable option for transit authorities with over 50 light rail lines in the U.S. currently in the planning phase[1]. This outcome was predicted in the lifecycle model shown in figure 1. Maturity of this transportation mode has not occurred and growth is expected until 2048.

The Predecessor: Street CarsEdit

Street cars lines ran across every major city from the 1890s to the 1930s and provided affordable and reliable transit for the masses that had previously been unavailable. After the initial street car boom had run its course, the price of fares increased to fund infrastructure replacement and maintenance. This dilemma made bus lines increasingly competitive with the street car market because they were cheaper and more maneuverable. As street cars transitioned from track to trolleybus, so too did the ownership of these systems. Originally, street car lines were owned by private companies that turned a profit on the system. However, when the industry began to collapse in the 1930s, local governments took up these systems in order to offer some form of public transit to their citizens. Demand for public transit dropped in part due to the rise in the median income which made the automobile affordable and the change in the work week from six to five days[2]. Despite these efforts, street cars and trolleybuses were rapidly abandoned as the prevalence of automobiles began to saturate the personal transportation market.

Development of the TechnologyEdit

The features that distinguish light rail from its predecessor lie in the operating characteristics and trip type serviced by the system. Unlike street cars, light rail trains move faster than street cars which makes them eligible for serving both long and short distance trips. Light rail lines may be elevated or use a tunnel for some distance in order to preserve the existing corridor. The interior of a light rail car has always been designed for comfort as opposed to the minimalist approach of the early street car systems. Furthermore, the brakes and shock absorbers of light rail are far more resilient to translating perturbations than the street cars of late. Many of these passenger comfort ideals resulted from the Presidents’ Conference Committee street car design which attempted to improve ridership by equipping street cars with similar luxuries to an automobile[3]. To differentiate between a modern street car system and light rail system, several factors should be compared simultaneously. Usually, light rail systems have dedicated lanes, off-street tracks, larger vehicles and multiple cars per train while street cars only occasionally have these features. Additionally, light rail systems have long route lengths and long distances between stops while street cars have short routes and short station separation. Because light rail was adopted in areas that had previously been operating street car lines, the infrastructure was only partially modified in some cities and as a result, there is no clear cut distinction between the systems. Key technology that defines light rail from other transportation modes includes the use of a pantograph (or trolley pole) to grab electricity from overhead wires, fixed routes and time tables, and right-of-way that is physically separated from surrounding traffic. Light rail vehicles tend to load at elevated stations or use low-level steps for boarding. There are generally two categories of light rail systems, low and high capacity. A low capacity system may be set amongst traffic, have frequent stops, and lack a platform for passengers to use to board. Low capacity light rail systems can sometimes include lines that are separated from the surrounding traffic, have fewer stops, and a dedicated area for boarding. In contrast, a high capacity light rail system touches a fine line with metro systems (such as the London Underground) however they are usually considered light rail if the train itself is short and the frequency is low. Cities looking to alleviate congestion and transport a low to medium number of citizens across a frequented path are a prime market for light rail development. The term “light” rail implies that the frame of the vehicle weighs less than freight and commuter rail which tend to run longer distances and sustain heavier loads than a light rail train. Additionally, light rail trains can be comprised of one car or multiple cars strung together which creates versatility for the uses of light rail.

Market ForcesEdit

Street cars were commonly seen as uncomfortable, dangerous and difficult to turn a profit on. Automobiles corrected many of these problems by allowing people to travel on their own terms and by utilizing the free road system. Automobiles took over the transportation industry for the better part of the next 30 years before awareness for mass transit was raised again in later decades. By the 1960s, cities began to experience the drawbacks of increased motorization. At this time, traffic congestion was reaching new heights and superhighway development was destroying neighborhoods and their surrounding economies. By the 1960s, mass transit ridership had fallen by 58% from the late 1920s and many thought that mass transit would remain grounded for years to come[4]. Contrary to this belief, transit saw a renaissance during the early 1970s as transit visionaries and urban planners began to look towards Europe for building back the mass transit system that had been lost. During this period, the American public was becoming increasingly politically active and this spurred feelings of optimism about the idea of changing the course of technological progress in the country. The conversation to bring light rail to North America came about in the 1970s after the oil crisis became a prevailing issue. This was also a time when transit agencies were searching for new technological advances[5] to improve congestion and the flow of citizens through the city center. Additionally, defense contractors were looking for alternative markets for investing money after the Vietnam War and public rail transit was seen as a growth area. Problems with congestion in major U.S. cities was becoming an increasingly important topic and light rail was the seen as the solution to crowded urban regions while providing an environmentally friendly transport mode. Overall, rapid transit was a desirable service for U.S. cities and a vision to bring rapid transit at a fraction of the cost became the backbone of the light rail movement.


The Urban Mass Transportation Assistance Act[6] of 1970 gave funding to new rapid transit systems which jump started the light rail revitalization across the U.S. In fact, in 1972 the term “light rail” was coined to distinguish the new mode from the old street car technology. This distinction was necessary in order to avoid negative public perception of new rail lines. A standard light rail vehicle (SLRV) was created by the Urban Mass Transit Administration (UMTA) in the hopes of reducing the price of light rail transit (LRT) systems. However, the first production which was led by Boeing Vertol was executed poorly and many of the 150 cars sent to Boston and 100 cars to San Francisco had problems. Michael Taplin, past chairman of the Light Rail Transit Association has said, “Boeing tried to reinvent the wheel rather than learning from transit vehicle experience elsewhere” (1998)[7]. Despite the issues with the first implementation, awareness was raised for light rail systems in America. The first U.S. city to newly adopt light rail was San Diego with its first line opening in 1981. The definition of light rail was changed in 2011 by the Bureau of Transportation to include street cars and hybrid rail. This change reflects the similarities between the operating conditions and infrastructure that light rail, street cars and hybrid rail transit require. Light rail networks may have characteristics that align them more closely with commuter rail (commonly referred to as “light metro”) or even tram-like systems when they are operated alongside personal vehicles. In contrast, light rail systems tend to have exclusive right-of-way while the traditional streetcar systems operated in mixed traffic conditions. As a whole, light rail definitions have taken on a variety of forms in cities across America but usually the term light rail refers to any local passenger rail system. Increased development along a light rail corridor is frequently noted as a benefit to building such a system. The light rail transit vehicle market revenue was 8.48 billion as of 2012 and has been projected to reach 11.5 billion by 2020[8]. Urban light rail systems compete with bus rapid transit systems (BRT) for market share because they have a similar capacity (20,000-25,000 passengers/hour) but they cost four times less to construct than a light rail system.

Light Rail at MaturityEdit

While light rail has not yet reached maturity, plans are underway for improving the existing facilities and building better systems in the future. Transportation and urban planners are now better able to forecast the needs of the future and in doing so can provide society with superior long term plans. This planning will hopefully enable transit authorities, investors and transit users to maximize the mode well beyond its expected date of maturity. To achieve optimized light rail transportation systems, policies for compact development in areas that surround a light rail corridor will promote shorter trip lengths, offset the number of automobiles on the road and improve air quality for residents in these areas. Light rail systems are currently spearheaded by a government agency and private sector partnership, the light rail lines of the future will incorporate more community involvement to take part in the maintenance of the system (i.e. Adopt-a-Station ideology). The investment in light rail tracks and vehicles should be paired with station and corridor improvements in order to make the connecting points seamless for daily users and the occasional user. This will improve ridership because users will experience the ease of using the light rail systems. Additionally, stations will increase the use of sensors, communication devices and warning technology, each of which facilitate the use of the system and reduce collisions with automobiles and pedestrians. Plans for the area surrounding a station will become increasingly relevant as multimodal corridors become essential for connecting light rail riders with their final destination. The limits to the area of available right-of-way is a problem that will continue to persist if not increase, thus sharing space with other facilities will become increasingly common (i.e. Twin Cities Green Line light rail and Metro Transit buses along Washington Avenue). The objective of any light rail design is to incorporate transit-compatible land use to ensure future development aligns with the trips captured by the current system. By encouraging land use that will maximize the light rail route, instances when demand peaks near particular locations (i.e. near stadiums, universities, shopping malls, etc.) will be easily diffused by providing special schedules for these areas. Adapting the light rail train to these situations will improve the customer base in areas where job centers are dispersed. Light rail transit should continue to serve as “an element of a larger multimodal transit system” (Campion, Larwin, Schumann, & Wolsfeld). These lines are easily viewed as a single entity however, transportation planners and urban planner should continue to design light rail transit with the idea of distributing passengers from larger transit modes (commuter rail, airports, etc) and collecting from the suburban bus feeder lines. These practices will position light rail for a bright future indeed.

The Light Rail Lifecycle ModelEdit

The lifecycle of light rail was analyzed using the S-curve as a model for the birth, growth and maturity of the transit mode. The data were taken exclusively from the Bureau of Transportation Statistics online database[9]. The passenger miles traveled on light rail annually beginning in 1980 (Table 1-40) was used as the metric for the lifecycle analysis. Data were listed as unavailable before 1980 because the first light rail system in the U.S. did not open until 1981, thus no information should be available. The definition of light rail changed in 2011 to include street cars and hybrid rail. To compensate for the added forms of transit, a list of street car/hybrid rail lines was compiled for the years 2011-2013 in which the original data might have been inflated due to additional rail lines being considered as light rail. In total, ten street car line opened across the country during this two year span and an estimate for their respective contributions to the passenger mile count was subtracted from the original data for years 2011-2013. Once the data had been cleaned, a regression analysis was performed to parameterize the S-curve model. Equation 1 was used to estimate a three-parameter logistic function in which K and b needed to be estimated. The saturation level for light rail has not been reached at this point in time so K was estimated by testing a list of values and performing logistic regression to determine the K value of best fit. Figure 1 gives a visual representation of the multitude of K values that were tested through linear regression. Using this method, the best value for K was equal to 5400 million passenger miles annually. At this value, light rail passenger miles will taper and stay in the mature phase. The results of the regression analysis conducted to find K also gave a value for b (see table 1) which was used in the three parameter logistic model to predict the expected system growth. The inflection year t0, which is the year in which half of the potential system growth has been reached, was found to be 2014. Using the values identified for K, b, and t0, the three parameter logistic formula was applied to the given years (1980-2013) and used to create a prediction for the passenger miles. The final logistic function predicted an S-curve that generally adhered to the actual passenger miles traveled. To test the accuracy of the model, another linear regression test was performed on the predicted values. The R-Squared value passed at the 5 % significance level with a value of 0.9575 (see table 2). From figure 2 it can be seen that the birth of light rail in America began in 1980 and grew from 1985 to 2014. The transit mode is predicted to reach maturity by 2048 with approximately 10800 million passenger miles annually.

Lifecycle Modeling ResultsEdit

Equation 1: S(t)=K/(1+exp⁡(-b(t-t_0 )]) Sample Calculation: S(1980)=5400/(1+exp⁡(-0.0847(1980-2014)])=286 million passenger miles Maturity year=2014+(2014-1980)=2048

Definition of VariablesEdit

S(t)= Passenger miles traveled t=Time (years) t0=The inflection time (year in which 0.5K occurs) K=Saturation level for passenger miles traveled. b=Coefficient of the three-parameter logistic function.

Table 1. Key Values for Light Rail S-Curve Model Equation.Edit
K= 5400
b= 0.0847
t0 2014
Table 2. Results from the Predicted Passenger Miles Linear Regression.Edit

Regression of Predicted Passenger Miles K=5400 Regression Statistics R Square 0.9575 Standard Error 138.9 Observations 26

Regression of Predicted Passenger Miles
When K= 5400
R-Squared 0.09575
Standard Error 138.9
Observations 26

Figure 1. R-Squared Plot Generated from Testing K Values-K=5400 million Marked in Green.

R-Squared plot

Figure 2. Comparison of Actual and Predicted U.S. Light Rail Passenger Miles (Millions)


Freemark, Yonah. "Planned Light Rail Systems." The Transport Politic. N.p., 2015. Web. 11 Nov. 2015. <>.

Garrison, William L., and David M. Levinson. The Transportation Experience. New York. Print.

Post, Robert C. Urban Mass Transit: The Life Story of a Technology. Westport, CT: Greenwood, 2007. Print.

Thompson, Gregory L., Florida State University. 2003. Defining an Alternative Future: Birth of the Light Rail Movement in North America. Transportation Research E-Circular (E-C058). [Accessed Nov. 09, 2015]; Portland Oregon.

Garcia, Jeannette, Frost and Sullivan. 2014. North American Light Rail Transit Market in North America Becoming More Competitive. Strategic Analysis of Light Rail Transit in North America (NC3D-13). [Accessed Nov. 03, 2015]; Mountain View, California.

Currier, Reasa D., ed. "Public Transit: Looking Back and Moving Forward."Journal of Advanced Transportation J. Adv. Transp. 44.3 (2010): n. pag. Web. <>.

Taplin, Michael. Light Rail Transit Association. 1998. The History of Tramways and Evolution of Light Rail. [Accessed Nov. 07, 2015];

Campion, Douglas R., Larwin, Thomas F., Schumann, John W., Wolsfeld, Richard P. 2000. Committee on Light Rail Transit. Light Rail Transit: Future Opportunities and Changes. [Accessed Nov. 10, 2015]; Washington, DC.

"Table 1-40: U.S. Passenger-Miles (Millions)." Bureau of Transportation Statistics. United States Department of Transportation, 2013. Web. 11 Nov. 2015. < >.

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