Sounds like this would fix so many problems with cars today, simply by making car ownership something to be dreaded, not desired. From traffic jams and traffic accidents, to car-dependent neighborhoods and cities - all solved by preventing general population from building their lives around driving. Even salaries for drivers of delivery/logistics and utility vehicles, as hazard pay would apply.

Now, a spike may be a good reminder, but practical solution might be more along the lines of mandatory redesign of safety features like crumple zones, so that energy of impact is dissipated primarily into the space occupied by the driver.

(Bonus: that still leaves all the energy dissipation options currently present on the table, so cars would be strictly safer for passengers.)

... Huh?

No, I'm saying -- and I can't believe I have to spell this out -- that pedestrians should be rolling around inside giant steel spiked balls like sea urchins.