Crazy Accident

toedtoes wrote:

K3WE wrote:
Beemerphile...your little merge cartoon is just that- a cartoon.

Your "right way to merge" only works when traffic is light. It would require that the highway be operating at less than 1/2 capacity getting shoved into one lane that would then be near capacity (or actually still less than full capacity if you want things to go smoothly). So again- "light traffic is required"

However, if both lanes are anything more than halfway full, when they merge to one lane, they are MORE than full and folks have to start slowing down to address the improperly short following distance that results.

And for the situation where both lanes are "essentially full" to start with...do your math...suddenly the following distance is cut in half (more than half since there's a vehicle in there too), so speed must be cut in half and things simply choke down.

I agree that merging could often be more graceful, but it's not a matter of a pretty little cartoon and it's not going to prevent a backup.

If everyone maintained the 3 second minimum distance from each other, then it does work. It does not slow traffic down. It does not make you late for your appointment. It does not give a@@holes the advantage over everyone else.

Try it once in heavy traffic. See how much easier it is to maintain a constant speed rather than the stop & go. See how much easier it is for others to switch lanes without having to make unsafe cuts, etc. It's great for the blood pressure also.

Certainly leaving reasonable following distances does help traffic flow in general. But arguing that a lane closure won't slow you down when you're maintaining a decent following distance and the road is reasonably close to capacity is incorrect.

For example, consider two lanes with average four second following distances. You have approximately 15 cars per minute in each lane, or a net flow of 30 cars per minute. Now let these cars all merge together into one lane, with a 3 second following distance. The net flow is only 20 cars per minute; those extra 10 cars per minute need to go somewhere, and that somewhere is a backing up/slowing down traffic. The only way to maintain flow is to go to an average two-second following distance. This result entirely comports with common sense, as well; when a lane is closed, the capacity of the roadway is reduced.

(The math is making a bit of a simplification by assuming that vehicles themselves have no length, and thus the following times may be measured from vehicle nose to vehicle nose. At highway speeds, this is not unreasonable, though it will skew the results somewhat. The conclusion still stands.)