Ok let me try and make this make sense; when driving on the motorway/highway, why does traffic come to a slow or stop at some points and then speed up (with no obstructions/traffic lights etc) and flow freely with no change in the road or conditions?
If it’s clear up ahead, why do cars slow down or stop when nothing is blocking them in the distance? It’s like it slows down for no reason then just regains speed and traffic flows fine. Drives me insane
In: 8
Lots of great explanations for WHY traffic waves start and propagate backwards! The reason they don’t easily disappear is two-fold.
1. Constant steady flow of traffic. Person A causes person B to slow down, causing C to slow down, causing D, etc, etc. If every single person has to slow down because person A slows down, then the traffic wave will never go away. There has to eventually be a significant gap in traffic for some person (let’s say Z) where Z doesn’t have to slow down, or has to slow down *less.*
2. Acceleration and reaction time. Cars can slam on breaks faster than drivers are willing to accelerate.
When you combine these two problems, you get the following scenario.
A nice steady flow of constant traffic moving at 65 mph. Let’s label the guy in front Person 1, followed by person 2, etc, etc, down to person 9999.
Person 10 encounters a raccoon on the freeway and slams on their brakes to avoid killing it. This causes the initial traffic wave of people braking. By the time person 10 gets moving again, a large gap has formed between #9 and #10. If there is a large gap in space somewhere in this constant steady traffic, there will *always be a crunch of space* (a traffic jam) somewhere else. Imagine a necklace of beads, with every bead evenly spaced around it. If you spread two beads apart somewhere, you are squishing two other beads somewhere else.
A possible solution to a traffic wave like this is for person #10 to speed up (go faster than 65mph) to *catch up to where they are supposed to be. They are supposed to be right behind person #9.* Doing this will let person 11 catch up to where *they* are supposed to be (right behind person #10), and so on and so forth.
So you either have to have some significant decrease in cars on the road so that someone downwind of the traffic wave does *not* need to slow down,
or
The people affected by the slowdown need to *rapidly speed up to get back to where they are supposed to be*.
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