A new traffic change to speed up mass transit on one of Manhattan’s busiest crosstown streets was so successful on its first day that bus drivers had to slow down to keep to their schedules.

Under an 18-month pilot program that began Thursday, New York City will allow through traffic of buses and trucks only along 14th Street between Ninth Avenue and Third Avenue. The start of the program left 14th Street eerily quiet Thursday morning and rescued Metropolitan Transportation Authority buses from the stop-and-go traffic.

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