New York City ? A police car working ahead of Vice President Joe Biden’s motorcade was involved in a minor traffic accident Tuesday evening, but it wasn’t part of the procession and the vice president was unhurt.

Three unmarked police vehicles, with their lights and sirens on, were traveling 5 to 10 minutes ahead of the motorcade on Manhattan’s West Side and were checking traffic before Biden passed en route to an appearance on “The Daily Show with Jon Stewart,” chief police spokesman Paul Browne said.

The cars were going through an intersection when the second one collided with a livery cab around 5:40 p.m. Traffic had stopped for the police, but the livery cab driver pulled out around the line of vehicles and was trying to go through the intersection, police said.