I am pleased that the MBTA has recognized the importance of reliable, timely Orange Line service by committing to the purchase of 18 new subway cars [JP Gazette, July 6]. The purpose of the acquisition is to reduce intervals between rush hour trains by one minute. However, to achieve precisely that same goal, I wonder whether those same funds might be spent better by making the Orange Line just five miles per hour faster.

First, some background: The average speed of the Orange Line end-to-end is a leisurely 20 miles per hour, yielding a 33 minute running time, or at least 66 minutes for a round trip. To provide service at existing five-minute intervals, simultaneous operation is required of 13 six-car trains. The purchase of 18 new subway cars will make available three additional train sets, allowing peak travel service almost every four minutes (instead of five). The average rider would save about half the wait time between trains, or half a minute. That is helpful to be sure, but the trip remains ploddingly slow.

The MBTA could achieve the same four-minute frequency of service by speeding the line to an ordinary 25 miles per hour for a running time of just more than 26 minutes end-to-end. Not only would the trains be more frequent, they would run faster. The improvement in travel times would be several times better. A commuter traveling half the length of the Orange Line would save the half-minute wait for the train, and would also save more than three minutes by getting to the destination faster. That is almost 20 percent improvement in travel times, versus just three percent improvement by purchasing three new train sets.

The Big Dig increased average peak-hour speeds on I-93 downtown from as few as 10 miles per hour (mph) to more than 50 mph. A half-minute improvement in wait time for slow 20 mph Orange Line service is hardly comparable in magnitude. Transit speeds matter, and the MBTA ought to consider how they would improve our system by making it faster.

Doug Tillberg
Somerville