Wow, a good idea to stop accidents! In fact the speed will need to be gradually reduced to almost walking speed (3 kmph) over a period and they will still find vehicles ramming into each other.
After that it will be pure bliss, working/traveling... etc
from home. We will be back to the era of using horses, elephants and camels for transport
. And each of those animals will have speed governing belts around their legs!