Even being a responsible driver you are still open to the edge case that you are going 45mph on a road that has a 45mph speed limit, doing nothing wrong, and a child steps out into your lane. Larger, heavier vehicles basically guarantee a fatality at that speed. The event was entirely out of your hands, well within the random risks of these events while driving, but your choice of vehicle has now made it a much more dangerous situation when it didn't have to be so dangerous. Pedestrians are involved in a minority of auto accidents but a majority of fatal ones, so if your goals are to decrease the risk of death in the general sense every time you go out on the road, you'd do well to choose the lightest and most sloping faced vehicle available to you.