I've sat in traffic that suddenly slowed to a crawl, then sped up again without any accident, broken-down car or merging lane. It feels like the jam came from nowhere. I read that a single driver braking can cause a wave that travels backward through traffic, but how does that small slowdown become several minutes of standstill? Is there a simple mental picture for how these ‘phantom jams’ grow and eventually disappear?
Why traffic jams can appear without any crash or lane closure
- explain-simply
- traffic
- jams
- appear
24
3 replies
A tiny slowdown is like tapping the first domino in a row that’s already packed too close together. The delay spreads backward because every...
A tiny slowdown is like tapping the first domino in a row that’s already packed too close together. The delay spreads backward because every driver reacts a little late, so the little gap behind them gets bigger and the wave grows.
That’s the part people miss: each car doesn’t just slow once, it slows a bit more in response to the car ahead. The wave keeps moving back until someone far enough behind leaves a bigger gap and the whole thing starts to unwind.
I picture it like squeezing a hose. The water doesn’t stop because the hose broke; it stops because the squeeze moves along and then relaxes...