“To limit vehicle speeds through auto design or speed limiters is to encourage the production of inferior vehicles, likely with poor performance in other aspects of their operation.” When this is weighed up against reduced frequency and severity of collisions, it’s a trade off I think is worth it.

And you assert without reason that “To artificially lower speeds introduces greater problems.” I’m wondering how bad these problems are such that they are worse than more frequent and more severe collisions. You also suggest reducing speed may cause a greater number of collisions (once again without justifying it).

The rest of your post is about collision avoidance, and you seem to only consider same direction traffic (which from memory accounts for a very low percentage of collisions). Speed (relative to the ground) is most definitely important when considering stopping distance (important for pedestrians and traffic from sidestreets), and a factor in the severity of collisions when they do happen (especially with oncoming traffic).

Anyway, when we have gotten rid of car collisions, I’ll agree that limiting speed isn’t so important.

I’m not saying the rest of your points aren’t worth considering, they are just red-herrings that are not mutually exclusive with speed reduction.

I’m always shocked at newspaper articles I seem to read on a daily basis about drivers that have killed pedestrians, but no charges are contemplated or fined. Certainly some pedestrians cross roads at the wrong time, but it is the driver of the car who is responsible for the death.

To limit vehicle speeds through auto design or speed limiters is to encourage the production of inferior vehicles, likely with poor performance in other aspects of their operation. Driver and vehicle capabilities can reduce accidents through avoidance, which is better than simply having the same number (or greater) of lower speed collisions. If there is no accident, then vehicle speed is immaterial.

It is appropriate that roadway speeds are typically set at the 85th percentile. People generally know and drive at speeds appropriate for a given roadway segment. To artificially lower speeds introduces greater problems. If it is important to reduce prevailing travel speeds on a given roadway segment, then the geometric design of that road should be altered to promote driving at a lower speed. Conversely, the road might also be redesigned to eliminate harmful design elements contributing to accidents and injuries at current speeds.

A greater problem is lack of proper lane discipline on highways, and high speed differentials between vehicles.

It is impressive that auto related fatalities have remained substantially level for nearly a half century, while the number of autos, drivers, and vehicle miles travelled each year have all increased enormously.

“…about 90% of child pedestrians are killed by sober drivers.”

I look forward to reading you book. Thanks!

It is hard to combine stats. I have seen cites that 80% of accidents (not fatalities) are caused by driver inattention. This was tested by actually having volunteers drive around being recorded on camera (head and eye position) and waiting for them to have accidents. Of course, impairment (DUI) would cause inattention. So accidents could involve inattention, speeding and DUI at the same time.