Despite reports of 90-minute traffic delays at the Lincoln Tunnel last week in New York City and New Jersey daily newspapers, Port Authority of NY & NJ vehicle counts show that roughly 9,000 fewer vehicles used that crossing on Thursday than on the same day last summer. This 7% reduction is remarkable in light of the fact an emergency shutdown barred 98,000 cars and trucks from their normal weekday routes through the Holland Tunnel. 

Although vehicle crossing figures from Thursday were not available for the George Washington Bridge or the Staten Island bridges, it appears that thousands, and likely tens of thousands, of drivers either stayed at home, changed commuting patterns, or entered Manhattan by transit or carpool. Backups experienced at the Lincoln Tunnel cannot be explained by diverted traffic, but are rather likely due to police searches and by driver confusion and traffic constraints caused by the closure of the lower West Side Highway, streets around the PA bus terminal and other Manhattan avenues, streets and highways. The intriguing finding should lead transportation planners to analyze Port Authority, MTA, and the NY Thruway Authority toll crossing numbers from last week and coming weeks to better understand the effect of the closures.

If true, the fact that fewer people now drive into Manhattan would be only the latest example of the theory that cutting back on the amount of lane or road space available to cars and trucks actually reduces traffic. (The inverse of this maxim is that the more lanes and roadways constructed, the more people will drive.) A 1998 study of 60 cases of road and bridge closures in London by the Department of Transport found that on average 20% of previous vehicle traffic vanished after the closure (MTR #163). In San Francisco, after a 1996 earthquake forced the closure of the Central Freeway, CalTrans officials tracked a decrease in rush hour traffic along several major alternative corridors (MTR #101). Any work along these lines for NYC today would have to attempt to take account of job and other economic disruptions caused by the Sept. 11 crisis.

Shrinkage - February 27, 1999

No Traffic Jams After S.F. Freeway Closure - October 18, 1996

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