> Traffic flow theory looks tidy on a whiteboard, but real roads don’t follow V D L arithmetic. I have been paying attention to speed changes while driving for

> Traffic flow theory looks tidy on a whiteboard, but real roads don’t follow V D L arithmetic. I have been paying attention to speed changes while driving for the past 15 years and every time I have seen a speed change, I always observe a proportional change in the other variables, within the bounds of my ability to measure. For example, speeds drop when lane counts decrease, and the difference is in proportion to the reduction in lanes and change in vehicle density. The change in things in logically forced, since cars are not magically disappearing/appearing on the road. Empirical studies have long supported the 85th percentile for vehicle safety. The spillover effect is a new thing that likely will affect the design of the ramps for highways, but does not justify violating the 85th percentile. If we are going to consider other effects, how about the effect that happens when the roads no longer have the capacity to carry traffic from enforcing lowered speed limits? That will result in bumper to bumper traffic during rush hour, with enormous amounts of particulates and NOx released from having so many vehicles idling. These kill people both on and off the roads. This is a problem in NY where the low speed limits philosophy has been in effect for decades. The electric future cannot come fast enough. Of course, electrification does not solve the additional problem of people dying fairly quickly because ambulances cannot reach hospitals in a timely manner due to bumper to bumper traffic. It is really easy to take the position that high speeds are the problem, but that ignores the problems associated with lower speeds. That said, I owe you a thank you for the information about the AAA study. I had been unaware of that. Thank you for the information.