Employee was a passenger (driver's side rear) on a 4-man mantrip traveling outside at the end of shift. The mantrip hit a hole in the road, measuring 36"" wide x 36"" long and 2-3"" in depth, in the travel way and the employee shouted to stop. When the mantrip stopped the employee fell out of the ride. The employee complained of lower back pain, and numbness in left leg.