London Tube Train Careers for Four Miles Minus Driver

London’s busiest subway line was closed today after a runaway engineering train traveled for almost four miles (6.4 kilometers) toward the center of the U.K. capital without a driver.

The train became defective near Archway station in north London after undertaking maintenance work and was being dragged away from the city by an empty passenger unit when it became detached and began to roll southward. It passed six stations before halting at Warren Street as the gradient leveled out.