New York City claims to have improved traffic flow thanks to its Green Light for Midtown project, which in 2009 closed off to motorists the Times Square and Herald Square sections of Broadway in West Midtown. Before then, the diagonal trajectory of Broadway confused traffic patterns, created treacherous intersections with other streets and caused the most collisions in the city, according to project officials.

To measure the remedy’s effectiveness, the New York City Taxi and Limousine Commission (TLC) attached GPS units to 13,000 taxicabs that drove in the area of Broadway being studied. The idea was to measure traffic flow in autumn 2008, before the changes, and then in autumn 2009, after the changes. Since taxis make up about 45 percent of all vehicles in the study area, they provided direct observation of a large proportion of all trip-making there, according to the Green Light for Midtown Evaluation Report.

But suppose improvements in trip times were due to other factors, like the economic slowdown; perhaps the drop in employment, and therefore of people on the road, was the reason for smoother traffic. City researchers recognized that potential, so they simultaneously tested East Midtown. If the same improvements in traffic flow that happened in West Midtown also happened in East Midtown, researchers would know the changes in West Midtown were not necessarily due to Broadway’s closure.

The New York City Department of Transportation compiled the taxi GPS data collected by the TLC. The agency based its analysis on 1.13 million taxi trips during September 2008 and 2009 in West Midtown and 890,000 taxi trips in East Midtown during those months. Results published in the Green Light for Midtown Evaluation Report include:

Northbound taxi trips in West Midtown were 17 percent faster in fall 2009 compared with fall 2008; this compares with an 8 percent increase in East Midtown.

The speed of southbound trips declined by 2 percent in West Midtown, while East Midtown showed a 3 percent increase.

The speed of eastbound taxi trips improved by 5 percent and westbound trips improved by 9 percent in fall 2009 in West Midtown compared with a year earlier; East Midtown showed improvements of 2 percent for eastbound trips and 7 percent for westbound trips.

The city attributes these changes, which were mostly improvements, to its alteration of Broadway, the evaluation stated. It recommended making the changes permanent.

Andy Opsahl  | 

Andy Opsahl is a former writer and features editor for Government Technology magazine.