N.Y.'s 'Gridlock Sam' Weighs In on Purple Line Transit Options

Maryland, Virginia and the District are studying proposals to build transit lines, but few involve heavy train systems like Metro. In most cases, local governments would choose between light rail and rapid buses. Maryland's debate over which would be better for the Purple Line is a sign of things to come.

The letter below is from Sam Schwartz, a former deputy commissioner and chief engineer at the New York City Department of Transportation, who writes a traffic column, "Gridlock Sam," that appears in the New York Daily News.

While in city government, Schwartz co-invented and popularized the term "gridlock" to describe what can happen when street traffic locks up.

Now, he has a dog in our fight. Sam Schwartz Engineering was retained by the town of Chevy Chase to evaluate the Purple Line alternatives proposed by the Maryland Transit Administration.

Dear Dr. Gridlock:

I am responding to Ed Tennyson's letter [Dr. Gridlock, July 24], in which he recommended light rail transit over bus rapid transit for the proposed Purple Line. The letter made some erroneous and incomplete statements that are important to address, as they reflect similar misconceptions that have surfaced in parts of the Maryland Transit Administration's alternatives analysis study and in the public reaction to it.

Tennyson incorrectly assumed that bus rapid transit would run on "high cost foreign oil." That thinking is outdated and wrong. Advances in alternative fuel technology have buses powered by compressed natural gas, domestic biodiesel and hybrid electric combinations of those. Federal Transit Administration rules governing any bus rapid transit vehicles that would be purchased for the Purple Line mandate low emissions comparable to light rail.

Tennyson writes, "Buses last only 15 years, while light rail cars last 40 years." Actually, the maximum life of a light rail vehicle generally does not exceed 30 years. Light rail transit vehicles also cost about twice as much as bus rapid transit.

Tennyson writes, "Busways need extensive water runoff provisions to prevent damage," but in the transit administration's proposed Purple Line light rail transit alternatives, tracks would run on raised roadbeds and viaducts that would require new water drainage systems and could affect existing streams.

One of the administration's bus rapid transit alternatives, however, makes extensive use of streets, where drainage systems are in place, and these costs and impacts could be avoided.