Types of Rail Transit: Light Rail

In the early 1970s, when a few American cities contemplated rebuilding some of the streetcar lines that had been torn out over the previous several decades, proponents decided that the term “streetcar” sounded too old fashioned to appeal to voters and taxpayers. Instead, they coined the term “light rail” to distinguish their proposals from subways and elevateds, which collectively were dubbed “heavy rail.”

Confusingly, the terms “light” and “heavy” have nothing to do with weight. In fact, light-rail cars generally weigh more than heavy-rail cars. Instead, the terms refer to capacity. Most subways have platforms long enough to support trains that are eight to eleven cars long and have signaling that safely allows up to 30 trains per hour. If each car can hold 150 people, this gives them the capacity to move nearly 50,000 people per hour on a single track.

Light-rail capacities are much lower. Because most light-rail routes sometimes run in streets, trains of light-rail cars cannot be any longer than the length of a city block, or they will obstruct traffic every time they stop to load and unload passengers. Since light-rail cars are typically 90 to 100 feet long, and most city blocks are about 300 feet long, train lengths are usually limited to just three cars. A few cities, such as Portland, have even shorter blocks and can only run two-car trains, while a few others, such as Salt Lake City, have longer blocks and can run four-car trains. In addition, due to more frequent starts and stops, most light-rail signaling systems allow no more than 20 trains per hour, so the capacity of a single track in a city with 300-foot blocks is about 9,000 people per hour.

Light rail was supposed to be an inexpensive way to restore rail transit to a community. In 1981, San Diego opened a light-rail line that cost less than $10 million per mile (about $17 million per mile in today’s dollars). Built without federal funding, the line avoided some of the extra costs imposed by federal prevailing-wage, buy-America, and other requirements. But most importantly, the transit agency was operating on a limited budget and had an incentive to keep costs down.

Nearly all later light-rail lines were built with federal funds and costs rapidly spiraled upwards. In the 1980s, typical light-rail lines cost around $30 million per mile; in the 1990s, this increased to $50 million per mile; in the 2000s, this reached $100 million per mile. Seventeen light-rail projects proposed for federal funding in the FTA’s 2015 budget cost an average of $137 million per mile, ranging from $79 million per mile for a line in the Twin Cities to more than $900 million per mile for an underground line in San Francisco.

What does all this money buy? Not rapid transit, despite the fact that Dallas and some other cities use that term. According to the American Public Transportation Association, the average speed of light rail in 2012 was just 15.6 miles per hour. Although the average light-rail car has 65 seats and room for, perhaps, 85 more people standing, over the course of a day the average light-rail car in 2012 carried just 25 people.

Since 1972, light rail has come to mean something different from streetcars. The most important difference is that light-rail cars can be coupled together into trains of two to four cars. The Federal Transit Administration officially recognized this difference in the 2011 National Transit Database, prior to which it grouped streetcars and light rail together. Today, the lines in Philadelphia and New Orleans are classified as streetcars while the older lines in Boston, Pittsburgh, and Cleveland are classified as light rail.