A 2-foot-wide electric train once patrolled the Holland Tunnel between New York and New Jersey

A 2-foot-wide electric train once patrolled the Holland Tunnel between New York and New Jersey

Long before electric vehicles became mainstream, a tiny battery-powered railcar was already zipping through one of the busiest crossings in the United States.  The unique machine once patrolled the Holland Tunnel between lower Manhattan, New York, and Jersey City, New Jersey.  At just 2 feet wide, it rode on a narrow catwalk above traffic and carried police officers through the 1.6-mile tunnel at speeds of up to 12 miles per hour. Here's what to…