Tokyo's Haneda Airport is trialing a driverless vehicle to tow cargo containers in an attempt to get around labor shortages as the number of tourists flying into Japan soars. The vehicle at one of the world's busiest airports can tow up to 13 metric tons of containers, joint developers All Nippon Airways (ANA) and Toyota Industries said in a statement. It can pull up to six containers at a time, trundling between aircraft and airport buildings over a distance of around 2 kilometers with no driver in the cab. The Level 4 vehicle, meaning that it does not require human interaction in certain settings -- although a human driver can still request control -- has been in operation since July 1. The trial, the first at a Japanese airport, is part of government-backed efforts to innovate the air transport industry, and the companies aim to make the vehicle fully operational by the end of next year, they said.