Re: Why only private companies
Speed is however a massive factor.
It increases the energy involved in any collision. Since the energy is proportional to the square of the speed even relatively small speed increase makes a significant increase in the energy brought to the scene.
It decreases the time available to react to any situation - whether that be a mechanical failure or a human failure on your own or someone else's part. It also increases the distance required for that reaction to occur - compounding the difficulty.
Obvioulsy travelling at 30mph (relative to what?) doesn't kill, but the energy which does kill people is readily available at speed, and judging by the number of road deaths each year is beyond the capacity of many people to reliably control...