I was watching a civil engineer’s video where he mentioned that in some cases where there’s a traffic jam but no space to widen the road or increase lanes, engineers resort to making the road longer and/or decreasing the speed limit. How does that help?
My first thought was that it acts as a buffer but since it’s still the same road technically, the cars entering and exiting is still the same therefore the buffer would eventually be filled up and the bottleneck will pop up again.
Edit: for more context. The road is a 2-lane highway in a game video (cities skylines 2) which has no traffic light and only 1 or 2 exit ramps at the end into the city.
In: Engineering
> My first thought was that it acts as a buffer
It can do. This is particularly important when you have junctions with traffic lights. If the stretches of roads between the junctions are too short, then you can end up with situations where an entrance to a junction completely empties long before the lights have turned red. Though another way of dealing this is to sync up the lights in such a way that traffic can continue flowing into these stretches of road from the previous junction whenever the lights are green.
> decreasing the speed limit
On motorways/freeways/whatever, a big problem is the phenomenon of traffic waves. Even without any external causes, traffic naturally tends to bunch up, so instead of flowing smoothly at a slightly slower speed, everyone goes through a cycle of driving at their top speed and then stopping. Some models suggest that reducing the speed limits on these roads can actually increase the average speed under certain conditions. But it’s complicated and not all models agree, and it obviously depends on how reliably people follow the speed limits. You can get all kinds of paradoxical scenarios like this in transportation networks: another famous one is Braess’s paradox, in which adding an extra road leads to increased congestion (even ignoring any slowdown at junctions or induced demand).
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