Leave the vehicle and go to a low flat area.
I know it may seem like the “drive away”option is the best choice, however, think of it like this. If he tries to drive away, there is a chance he may drive right into it bc there is no evidence in the question that John actually knows EXACTLY where the tornado will be. Thus he should get to a low spot bc that is the safest spot during a tornado. Why do you think we get low whenever there was a tornado drill at school? Bc it’s the safest spot. Also, Tornadoes are like upside down cones that slowly get bigger as you go up. So therefore going to the top of a bridge would not be the best choice because the area/range of the tornado will be greater where is the lower you get the smaller the area/range will be