Re:Almost every speed limit is too low (2017)
by Noumenon72 on Thursday May 16, 2019 @10:10PM
(#19935577)
The reason I am going 5mph slower in this thought experiment is because a continuous stream of cars is merging in front of me from the other lanes. (What the OP called the 'pathological case'.) They are the reason the lane is slower, and because they are not in the other lanes, those lanes will be 10% faster.
With the pathological case being so benign, the real life experience is even better. You might get a car moving in front of you once a minute, and usually a few seconds of slower accelerating or coasting is all you need.
To me the thing that really slows down traffic is people not moving left to let onramps merge. I think that's because they are afraid of missing their exit because no one is leaving gaps.
That lowers the throughput (number of cars that complete a trip in your lane) by ~ 10%. Also, the faster lane is now probably moving closer to your speed behind you than the 50mph you observe (because you are causing cars going 45mph to cut off cars going 50mph that lane).
The arrival rate of cars won’t change because you chose to go slow. So, if the road can handle 10,000 cars per unit time with normal congestion, it can now handle ~ 9000. That means per unit time, there are 1000 new cars sitting in the stop and go backlog that you single handedly created by creating the gap.
This has been shown time and time by traffic simulations. It only takes a small handful of slow drivers to create massive backups.
Also, the number of traffic fatalities is proportional to the difference in speed between the fastest and slowest car, so, statistically speaking, by being the slowest car, you are murdering people.