The M15 bus rolled through Manhattan, traveling south along Allen Street. As it approached a red light at Hester Street, the signal turned green. Then the same thing happened a block down and again at the next intersection, allowing the bus to slice through the congested warren of Lower Manhattan streets at a surprisingly swift clip.

The run of green lights had nothing to do with luck — it was intentional, made possible by a special system that gives the bus the power to use its GPS system to turn traffic lights green or keep them green longer, a relatively cutting edge technology that reduces travel time.

“The lights turn green for the bus? Wow,” said Steve Matos, 32, who abandoned the subway when navigating steps with a cane became too difficult after he sprained a toe. “They should do it on every line.”

They do not and, in fact, the M15 is the exception. Though the system was introduced seven years ago, it operates on just 11 of the 317 public bus routes in New York City, even as the tool could significantly improve a lumbering and unreliable bus network.