Rail Systems Update: Reaching Critical Mass in Rail Transit

In science, critical mass identifies the point where the presence of sufficient materials or energy makes a process self-sustaining.

Rail transit system starts of every kind are underway from coast to coast and North to South. Add to that most of the systems 12 or more years old are expanding their network or at least adding rolling stock to increase the frequency and passenger capacity of services.

Rail transit is no longer simply the domain of a small number of advocates crying in the wilderness. Cities and their citizens are now demanding rail transit — even if the funds are not always there to build and sustain a system.

Finding Examples

One of the initial difficulties in selling the concept of rail transit to many metropolitan areas in the mid- to late-20th century was that so few Americans had any kind of contact with rail transit. Yes, some travelers had visited cities in Europe or elsewhere in the world that had a diverse and highly integrated transit network that included a variety of rail operations, but many administrators, from the local to federal level were not quite sure how some of these concepts would translate to the U.S. environment. Want to show your city council members or county commissioners a successful rail transit operation? Where would you take them without spending huge amounts of money?

However, slowly a growing number of cities and regions managed to act on the courage of their convictions or the urgings of transit advocates and implemented rail.

In 1981 San Diego led the way by opening its first line from the city center to San Ysidro at the Mexican border with a new generation of light rail vehicles.

By the end of the 20th century, all the major metropolitan areas of California, home of the American automobile culture, embraced a variety of rail transit options. California was now seen as an example of what could be done with rail transit.

Pace-setter San Diego also found the solution to converting existing rail corridors to light rail without cutting off service to rail freight customers — time separation. U.S. federal regulations prohibit mixing freight traffic with a light rail operation, though such operations have operated successfully in Europe for many years. San Diego’s operation compromised by permitting switching of freight customers in the late-night hours after the transit operation had shut down. That type of operation was also applied when the San Diego system opened its second line to El Cajon in the hills above the city.

Charlotte Showpiece

This year test operations are already underway on a partial segment of the Charlotte Lynx South Corridor light rail line, with revenue operation planned for November. The Lynx light rail, part of the Charlotte Area Transit System (CATS), is the first modern light rail system for the Carolinas, though a heritage trolley operation had helped lay the groundwork on part of the 9.6-mile South Corridor initial line. The heritage trolley operation will return after construction is completed for the Lynx system, sharing tracks on part of the line during off-peak periods.

At the same time, Charlotte is moving forward with plans for a commuter rail operation from downtown to Mooresville to the north on an existing Norfolk Southern freight line with excess train capacity.

The light rail line (then nearing completion, but not yet open to the public) will be a major showpiece when the American Public Transportation Assciation (APTA) holds its annual meeting in Charlotte in October. After touring Charlotte’s Lynx light rail line, many of the transit officials and municipal representatives will undoubtedly leave the city with a case of rail transit envy.

That, in part, illustrates the maturity of rail transit in the United States Transit planners now have a better understanding of which rail mode or combination of rail modes may make sense in a given corridor and what the economic trade-offs between each mode are.

Once the decision is made to implement a particular rail transit operation, the sponsoring authority now has access to a selection of experienced rail transit managers, including some who worked on getting a new system off the ground; a range of transit equipment provided by a variety of manufacturers spread around the country, some with considerable experience in rail transit around the world; and engineering and construction firms with rail transit experience that will not need to spend time determining how to do something the first time around.

Blending Technologies

While the basic distinctions remain between the major rail transit modes — light rail, heavy rail, commuter rail and even intercity rail, one of the major trends of the early 21st century is the blending of the technologies and approaches.

Once the main domain of heavy and commuter rail, signal systems are now being increasingly applied to existing and new light rail operations, which had once relied primarily on operation on sight.

Even the distinctions between intercity and commuter rail are beginning to blend. Is an in-state route, which makes multiple relatively closely spaced stops with multiple trains per day intercity rail or commuter rail?

Here North Carolina offers another example. State residents have long been able to make single-day round-trips in the corridor between Raleigh and Charlotte. The state-supported Amtrak-operated “Piedmont” leaves Raleigh early in the morning, arriving in Charlotte in late morning; it departs Charlotte late in the afternoon, arriving back in Raleigh around 9 p.m.

Meanwhile, the “Carolinian” (also state-supported) leaves Charlotte in the morning, arriving in Raleigh before noon. The train continues on to Washington, D.C., and New York City. The southbound schedule has the train departing Raleigh in the late afternoon and arriving in Charlotte in the evening.

The state has long looked at a third mid-day frequency, also to be operated with state-owned equipment, like the Piedmont.

Technically, these are all intercity trains, though, once the third pair of trains is added, passengers will be able to make round trips that require only an hour or two in their destination cities.

At the same time, in multiple locations around the country, a variety of rail vehicles based on European (and some Asian) designs — which do not meet the full U.S. standards for use in mixed traffic with freight trains — are going into service in a category becoming known as “diesel light rail.” Use of these vehicles still leaves open the same option for low volume freight operations on lines used for electrified light rail by the means of time separation, which has freights only going onto the line after transit operations have ceased for the day.

Recent and Current Projects

In addition to the already mentioned Charlotte project, the following are some of the highlights of other rail transit operations that either opened or expanded in 2006 or will start later in 2007. (Information on new starts is based in part on data compiled by the National Association of Railroad Passengers.)


  • January: Chicago’s Metra expands service on three routes, adding both frequencies and more miles covered.
  • February: Florida’s Tri-Rail commuter receives new diesel multiple unit (DMU) trains built by Colorado Railcar.
  • July: New Jersey adds one route mile and additional stops to its Newark light rail line.
  • August: Increase in frequencies on California Capitol Corridor intercity service. St. Louis’ MetroLink opens Shrewsbury light rail line.
  • September: Nashville, Tenn., Music City Star 32-mile commuter rail operation begins revenue service.
  • November: Denver RTD opens 19-mile T-REX light rail extension.
  • December: Sacramento, Calif., opens 0.6-mile extension of the RTD light rail system to the city’s Amtrak station.


  • January: Opening of half-mile extension to Little Rock, Ark., River Rail streetcar extension to Clinton Presidential Library.
  • April: San Francisco Muni J/Church line extension opens along Third Street.
  • Summer: South Waterfront Streetcar 0.6-mile Lowell extension opens in Portland, Ore.
  • September: Massachusetts Bay Transportation Authority (MBTA) to open 18-mile Greenbush commuter rail line.
  • Fall: Calgary to add 1.8-mile light rail extension to Ctrain northeast line.
  • Fall: Seattle South Lake Union 1.3-mile streetcar line to open.
  • December: Diesel light rail operation between Oceanside and Escondido, Calif., to start.

Light rail lines in San Juan, Puerto Rico, and Monterrey, Mexico, were also set to open in 2006, but had not announced specific opening dates.Construction is underway or was expected to be underway in 2006 for Portland, Wash., commuter rail and Austin, Tex., commuter rail.

Looking Ahead

The possibility of electrifying commuter rail operations in the San Francisco Bay area is apparently getting another look. If this first main line electrification project of this century gets the green light, it would raise interesting questions:

Should the catenary wire be high enough to clear double-stacked containers on freight trains? Though the initial segment being considered does not see double-stack traffic, other lines in the region do — and it would make sense to apply a single standard for all lines. If the catenary is aligned to clear double stacks, that could be some of the highest (above top of rail) catenary in the world and could pose problems for pantographs atop standard-height electric locomotives or electric multiple unit (EMU) equipment.

Should freight operations on the line(s) being electrified also be converted to electric operation? Who would build the equipment? Rail transit operators and planners are living in interesting times.

Ernest H. Roble is a North Carolina-based writer and photographer.