EE WAS DRIVING WINCH TRUCK, PASSING UNDERNEATH CAB OF D31 DRAGLINE TO GO AROUND THE MACHINE. OPERATOR DID NOT KNOW THAT 2 VEHICLES WERE ATTEMPTING TO PASS AT THE SAME TIME. THE LEFT SHOE CONTACTED THE WINCH TRUCK & PUSHED IT ONTO ITS SIDE & OFF THE SPOIL SIDE HIGHWALL. THE TRUCK ROLLED SEVERAL TIMES & CAME TO REST IN THE PIT. EE TAKEN TO HOSP. VIA AMB.; MISSED 5 DAYS.