[DarqWebster]

Slower not meaning safer is because a slower driver among faster drivers causes more lane-changes, which are a less-safe maneuver. Everyone travelling the same speed is the safest scenario, with slower then being safer, as impacts occur with less energy.

If everyone strictly obeyed the posted speed limit and treated it as both a minimum and a maximum speed, as driverless cars would likely aim to do, roads would be safer. The interim state of having both driverless and human-driven cars on the road at the same time is where problems may arise.