Was operating vehicle when all of a sudden it stop in the middle of the highway. Engine turned iff. Was able to crank back up but vehicle would not shift into drive, reverse or any motion gear. Vehicle stopped in the morgue of an active roadway which created an absolute critical safety issue due to oncoming traffic. Was able to push vehicle from the roadway in neutral but transmission will not otherwise engage. Very high probability that this issue could have resulted in serious car accident if vehicle had became disabled at a high speed.