Transportation Deployment Casebook/Life cycle of US LRT- Vehicle Miles


Looking back on industrial history, many of the great technologies have been known to change in levels of deployment, use, or presence. Often, technologies follow similar paths over time. In informal terms, technologies are slow to catch on, but when they do, they become popular fast, are universal, then peak, and their use is high, but no longer seems to be rising. This familiar story follows a graphical representation of an S-curve. The presence of a technology over often can be seen to go through three “life cycles”: birth, growth, and maturity.

The life cycles of technologies vary. Some are rapid—like the microwave—taking off shortly after they are released to the market. Others are much more gradual, taking many decades to become popular.

This report examines the life cycle of a technology that has become popular in the last half century. Light rail may owe its beginnings to streetcar, but since the early 1980s when the first “second-generation” light rail system went on line in San Diego, it has become a technology that caters to the fast-paced urban lifestyle. Now light rail transit (LRT) systems are popping up all over America. Although it is tough to say where in its life cycle this technology finds itself, this report takes an empirical approach to estimating the future of light rail transit.

Before presenting the statistical findings of the life cycle of light rail, some historical context must be presented to better understand how light rail became a popular mode in American cities, as well as the future of the technology.

Light Rail TransitEdit


The American Public Transportation Association (APTA) defines light rail transit (LRT) as:

a mode of transit service (also called streetcar, tramway, or trolley) operating passenger rail cars singly (or in short, usually two-car or three-car, trains) on fixed rails in right-of-way that is often separated from other traffic for part or much of the way. Light rail vehicles are typically driven electrically with power being drawn from an overhead electric line via a trolley or a pantograph; driven by an operator on board the vehicle; and may have either high platform loading or low level boarding using steps. [1].

Whereas APTA equates streetcar and light rail, many transportation researchers see these two modes as distinct. Public transit commentator Jarrett Walker discusses the distinction between the two forms in his blog Human Transit:

Light rail and streetcar technologies are, as a whole, more similar than different, but the terms as I hear them used belong to different categories of usefulness to the customer. I use the term light rail to describe something that's at least attempting to be rapid transit, by which I mean covering long distances fast by serving fairly widely-spaced stations rather than closely-spaced local stops. The term "light rail" was invented specifically for the contrast with "heavy rail," which is a competing alternative for the same relatively long corridors. Light rail often makes closely-spaced stops right in downtown, and may thus serve a "streetcar" function there, but it does this mainly for the purpose of providing good access to people who want to use its higher-speed segments. I refer to streetcars/trams only when I mean local-stop services, designed to do pretty much what local buses do. (Human Transit, 2012)

It appears as though the definition of, and the distinction between streetcar and LRT is different based on who is asked. Streetcars and LRT can serve a similar function in some cities or different functions within the same city. The major differences between the two modes appear to come from the distance of the entire line, the frequency at which the vehicle makes stops, the capacity of the train consist, and the travel lane.

Potential MarketsEdit

It appears as though more and more metropolitan areas are pursuing LRT as a viable option for urban transit. According to The Transport Politic, at least sixty LRT systems are being planned around the United States (Transport Politic, 2013). Of course, not all of these systems will receive the funding or political support they need to be deployed, but the numbers are informative. Light rail provides transit agencies the ability to connect major destination centers by providing a fixed and reliable to its customers. Light rail is often politically popular because of the jobs the construction of the system creates, as well as the economic development that these systems often spark along the corridor.

Not all markets are appropriate for light rail, however. The investment is large. In the Twin Cities, the new Green Line LRT was set to open in mid-2014 and connect the two downtowns of Saint Paul and Minneapolis. The Metropolitan Council (the local Metropolitan Planning Organization) has said the 11-mile project has a budget of up to $957 million. Estimates for another Twin Cities LRT project, the 12-mile Southwest LRT (or Green Line Extension), has received price tags of up to $1.25 billion. Metropolitan areas must determine if the investment will produce the ridership and economic development to justify the cost. All transit requires a certain amount of residential density to support the system. Without zoning and land use to support this density, no one will ride the light rail. Some systems perform better than others. The extensive Boston light rail network had an average of 227,000 average weekday riders in the second quarter of 2013, while the Sprinter light rail in San Diego only saw 4,300 weekday riders during that same time. Boston has a robust light rail system that offers any connections to a densely populated metropolitan area, whereas the single line existing in San Diego operates between two cities whose populations do not exceed 200,000.

Before Light RailEdit

In many areas around the United States, buses dominated, and still dominate urban public transit. Buses have a high capacity, are relatively inexpensive to buy and maintain, and run on the same infrastructure as cars—no capital upgrades must be made for buses. Many cities have created a large network of bus service, and continue to operate on the same platform on which they began.

It is curious however, that buses replaced a system very similar to light rail. Between the late 1800s and the mid 1900s, streetcars dominated urban public transit. However, with the advent and affordability of the modern automobile in the early twentieth century, people no longer required streetcar service, and track was ripped up across the country. Eventually, buses, many of which followed the same routes, replaced the service of streetcars. In the beginning of the second half of the twentieth century, it seemed as though American public transit was doomed.

Indeed, the term “light rail transit” did not appear in North America until 1972, and the National Conference on Light Rail was held in Philadelphia in June of 1975 (Thompson, 2003). Taking cues from Europe and Edmonton, Canada, in 1981 San Diego was the first American city to adopt the second generation streetcar, or what is now called by it’s current name, light rail. This system is not the same as the SPRINTER system mentioned above currently serving Oceanside and Escondido, but instead was a 15.9 mile route that rain south out of downtown San Diego to the U.S.-Mexican border. The current San Diego Trolley still runs that same path as the South Line.

With suburban populations and automobile traffic congestion growing throughout the second half of the twentieth century, local governments began looking at options besides bus to help alleviate some of the issues related to the private automobile. In addition, transit agencies thought the clean and sleek light rail would be seen as a more attractive option for customers. Not only could the average bus rider take the light rail, but also the businessman, the politician and the doctor. By investing in corridors that connected major job centers, transit agencies aimed to capture riders who not only relied and required public transit, but also those who would willingly take light rail instead of driving their car to work.

Just as spatial distributions of populations changed after World War II that made streetcars no longer feasible, populations are returning from the suburbs and are now interested in living in the city, in denser settings. These demographic changes are making fixed guideway systems like LRT more possible. If more people live within the catchment area of a light rail station, the ridership is forecasted higher, and the investment no longer seems unviable. Since 1981 when the first American light rail system began operation in San Diego, light rail has grown in popularity, and will be discussed further in later sections.

Invention and Adoption of Light Rail TechnologyEdit

Light rail transit technology did not begin with a new invention, but rather the evolution and adoption of an existing technology. As mentioned, even today, many in the public transit field believe there is little difference between the technologies of streetcar and light rail, but rather in the implementation of the two. The vehicles of current streetcar systems and light rail systems are not terribly different. Both have low floors, both are powered by overhead electrical lines, and are operated by a single conductor. The San Diego Trolley began with German-built Siemens-Duewag U2 vehicles, but as the system has expanded and built an additional two lines, the system now utilizes updated Siemens Avanto S70 vehicles, which are used in both light rail and streetcar systems worldwide.

Market DevelopmentEdit

Light Rail was initially seen as a transit mode to reclaim the niche that was left vacant by the loss of streetcar. As trunk corridors were becoming overcrowded with automobile traffic congestion, LRT sought to connect major trip generators in trip times that buses alone could not accomplish. Currently, bus rapid transit (BRT) is also seen as a mode to fill this market niche, however, BRT vehicles are unlikely to be able to carry the same capacity as a LRT consist. In addition, BRT is not believed to have the same kind of economic development generating potential as LRT. Unlike an agency’s ability to “pick up and move” a BRT route, once LRT track is laid, the likelihood of the relocation of this line is slim. On the side of the spectrum, heavy rail has the capacity to more people than an LRT might, however, these heavy rail systems are more expensive and unlike an LRT, run usually on diesel locomotives, which carry with them environmental air pollution externalities (VTA, 2007).

It seems as thought LRT has found a transit market: one that can connect destinations of relatively long distances, can carry a large number of people separate from automobile traffic, may generate economic development in areas that may not be profitable, and is not cost (both financially and environmentally) prohibitive.

Historic Life CycleEdit

Now that elements and history of light rail transit have been touched on, this report will now discuss the findings of a statistical estimation of the lifecycle of light rail. This analysis attempts to estimate the future of light rail deployment by considering past and current trends in annual vehicle total miles traveled of all United States light rail systems. The analysis considers data between 1981 (the first “second generation” streetcar deployment in the United States) to 2011 (last reported data).

Presented in Figure 3 are the reported and predicted LRT miles from 1981 to 2011. As the reader can see, the model closely predicts the reported miles traveled. Also illustrating the accuracy in prediction is Figure 4, which graphically illustrates the reported and predicted annual miles traveled.

Figure 3. Reported and Predicted U.S. Light Rail Travel, 1981-2011
Year Vehicle Total Miles (millions)-Reported Vehicle Total Miles (millions)-Predicted
1981 16.5 13.02
1982 16.1 14.0
1983 16.0 15.04
1984 16.8 16.17
1985 16.5 17.37
1986 17 18.66
1987 18.4 20.03
1988 20.8 21.51
1989 21.3 23.09
1990 24.2 24.78
1991 27.6 26.59
1992 28.6 28.51
1993 27.7 30.57
1994 34.0 32.77
1995 34.6 35.11
1996 37.6 37.61
1997 41.2 40.26
1998 43.8 43.09
1999 48.7 46.09
2000 52.8 49.28
2001 54.3 52.66
2002 61 56.25
2003 64.3 60.04
2004 67.4 64.05
2005 69.2 68.28
2006 74.3 72.75
2007 83.9 77.45
2008 88.5 82.39
2009 90.7 87.57
2010 93.6 93.01
2011 89.2 98.7
Annual U.S. LRT Mileage

By projecting reported data into the future and determining which model was most accurate by examining the coefficient of determination (R2), an estimate can be made at which the miles traveled of all U.S. LRT will peak. Several estimates of peak mileage were made ranging from 95 million miles traveled to one billion miles traveled. After these estimates, the point of highest coefficient of determination yields the most accurate prediction of peak mileage. The highest coefficient of determination occurred at the estimate of 475 million miles. Before this point, LRT mileage traveled increased every year. After this point, mileage decreased every year. Figure 5 illustrates the projection of this model into the future. As illustrated, the model predicts increasing vehicle miles traveled, then a leveling off, and eventually reaching a maximum close to 475 million miles. This maximum of 475 million miles is never reached, but the model predicts a negligible gain (and statistical asymptote) in annual mileage traveled starting in the year 2095.

Annual U.S. LRT Mileage Taveled, Future

Finally, this analysis gave an inflection point, or where the vehicle miles traveled slowed in growth. In other words, this point shows does not show where LRT mileage is expected to stop increasing, but rather where the mileage ceases to increase at an increasing rate and begins to increase at a decreasing rate. This point was estimated to fall in the year 2029.

From Figure 5, it is possible to affix birth, growth and maturity stages in the life cycle of LRT. These dates are suggested by looking at both the graphical representation of the projection, as well as the reported vehicle miles traveled.

• Birth: First Implementation → Rapid increase of deployment

o 1981 – 2010

• Growth: Rapid Increase of deployment→ inflection point

o 2010 – 2029

• Maturity: Inflection point → asymptote approach

o 2029 – 2095

Policy in the Birth and Growth PhaseEdit

With regards to the initial light rail transit system in the United States, the San Diego Trolley, federal legislation passed in the early 1970s to promote public transit through $12 billion was encouragement to San Diegan MPO (then called a Comprehensive Planning Organization—or CPO) to develop a mass transit plan. (Thompson, 2003) Furthermore, then California Senator James R. Mills was a large proponent of transit, and pushed for the deployment of what would become the nation’s first second generation light rail system.

It is possible that LRT remains in the birth phase, or likely in the early stages of the growth phase. There are current federal, state and local policies that encourage the deployment of rapid modes of transit (one of them being LRT). Examples of such policies at three governmental levels: • Federal: Moving Ahead for Progress in the 21st Century Act (MAP-21) was a bill signed by President Obama that funds $105 billion of surface transportation programs in both 2013 and 2014. • Minnesota: Non-Urbanized Area Transit Assistance Program • Local: A dedicated 0.25% sales tax was established in 2008 with the formation of the Counties Transit Improvement Board


Light rail transit has roots in past streetcar systems that once dominated American transportation. For decades, streetcars shaped cities by changing development patterns, connecting neighborhoods, and leaving others in isolation. These routes were later taken over by buses, and only since 1981 have second generation light rail systems similar to those in current use been deployed. As this exercise in life cycle deployment analysis shows, at the rate American cities are investing in this transportation technology, it appears as though light rail transit will continue to expand.

  1. "2013 APTA Factbook Appendix". American Public Transportation Association. 2013. Retrieved 2013-11-05.