Risk compensation is one potential problem with wearing a helmet... I imagine seat belts have a similar effect, as might drivers wearing helmets. Based on this idea backwards, I've read a proposal to add a spike to steering wheels to reduce dangerous driving.

I recommend watching car crash compilations. They definitely help you feel the risk of driving on an emotional level. I feel I've learned some things that improve my driving safety, but probably the biggest safety gain is I just tend to drive more cautiously due to car collisions being very present in my mind.