Time of flight laser scanners (LIDAR). Scanners on each side of the truck measure the shape of the wall. you drive the truck down the tunnel once (in one system

Time of flight laser scanners (LIDAR). Scanners on each side of the truck measure the shape of the wall. you drive the truck down the tunnel once (in one system) it stores a map of the wall shape and then follows the same shape to keep the same distance form the walls. Another laser scanner checks the tunnel ahead (and behind) for obstacles, other trucks, people, rockfalls etc. On some systems a spinning laser on the top hits fixed prism reflectors with known position on the roof and walls, it constantly resects it's position from this.