Why am I stuck in traffic for an hour, only to find no wreck!

[Alzarian]

Surely this has happened to you. You're cruising home after a long day of work, only to get caught up in a traffic jam. So you patiently stop and start, creeping forward inch by inch for upwards of an hour. And what do you see when the traffic actually starts moving again? NOTHING!

Why does this happen? Was there a wreck there hours ago, which even when cleared away, still causes traffic to bunch up? It's just so insane.

Maybe there needs to be signs which display "Traffic problem cleared. Everyone go please in ten seconds." Count down from 10, and when zero is reached, all cars move forward.

Ok, wishful thinking, but it is a question that always bothers me when stuck in traffic...

[Anachronism]

Cecil answered this one --No stoplights on the freeway, so why does traffic halt?

[Saltire]

This guy has done a lot of thinking about this phenomenon. Check out the cool animations and insights here: http://www.eskimo.com/~billb/amateur...c/trafexp.html

I've tried his method, and it seems to work. Unfortunately, there are just too many drivers that seem to think they'll get home faster if they are 15 feet from the car in front of them than if they are 40 feet away.

[handy]

"Was there a wreck there hours ago"

Close, its actually about 5 hours. I remember some people who did a study of this on TV. They used cameras & noticed that, strange as it may sound, but the backups don't happen right away but a few hours later.

[Saltire]

I posted one of the middle pages of his site. It actually starts here: http://www.amasci.com/amateur/traffic/traffic1.html

[hapaXL]

isn't it just a myth that you need a wreck to create a traffic jam? i thought that when too many cars enter the road, there will be a backup.

such a myth would help us keep believing that the highways might be able to work properly. instead of seeing that busy freeways will always have traffic (even if you add lanes--that just makes more people drive), we fool ourselves into believing, "i'd be cruising at 60 mph if it wasn't for that fool who caused the accident."

[WillGolfForFood]

i thought that when too many cars enter the road, there will be a backup.

Eventually there will be, yes. It's a predictable phenomena using queing (queueing?) theory.

When there's not a lot of traffic, momentary slowdowns (say, when you take your foot off of the gas momentarily as you change radio stations) filter out - the car behind you is far enough away so that he slows down less than you so, as does the car behind him, as does...

When there's too much traffic, however, those momentary slowdowns magnify rather than decrease - until folks end up at a dead stop "for no particular reason".