Braess’s paradox
en.wikipedia.org
en.wikipedia.org
This paradox may have some relevance to the effect of navigation apps, especially those that attempt to route around congestion, as they effectively create routes in the sense that the vast majority of drivers would not have considered using them without the app.
Ultimately, the only way to have optimal flow is to delegate all itinerary decisions to a central authority...
This may be the result of better predictive modeling, and particularly in recognizing that dumping a lot of traffic into a low-capacity route is pointless. It is probably also a political response to the fact that residential areas don't like having a lot of traffic routed through them, and are pressing for the power to regulate it.
Better predictions could also explain toast0's observations even when global optimization is not being attempted.
Improvement in roads always lead to more cars, beyond what was expected. Entire suburbs get created when roads improve!
From the article:
"the removal of main roads does not cause deterioration of traffic .../... some motorized travels are not transferred on public transport and simply disappear ("evaporate")."
But this paradox appears to hold traffic constant, and uses game theory to show how more connections (not lanes) can result in worse congestion too.
It really is amazing how something as simple-seeming as roads and traffic, where it feels like simple common sense ought to apply, winds up being so deeply and fundamentally counter-intuitive.
[1] https://www.amazon.com/Traffic-Drive-What-Says-About/dp/0307...
This is not the paradox nor even an argument against adding road capacity though.
Even if congestion or travel times stay the same, now more people are able to travel to places they want to go. Traffic might not have improved, but some measure of quality of life did.
Peak demand will always saturate whatever capacity you have but the amount of stuff you move at peak capacity is greater so you spend less time fully saturated
That doesn't follow.
Beyond two submissions sharing the same subject-title, do you think it'd be possible to find all "relevant" discussions -- say, back-links or forward-links -- as well and post them?
However, there is a good, clear demo of the spring experiment at https://www.youtube.com/watch?v=ekd2MeDBV8s
This is when the same amount of traffic is distributed less optimally because of adding new edges on the graph.
This actually happened in my home city, some areas implemented "improvements" that made it very difficult to reach some destinations, you need to follow long detours intended to "improve flow", they might improve flow for whoever is just passing by, but traffic that originates or terminates in that area, it is hell.
The latest Sim City had its problems, but I definitely experienced this phenomenon in its traffic simulation. Adding more roads created more intersections which -- using a computer analogy -- created more context switches between competing cars (threads). Intersections would become clogged, potentially backing up nearby intersections. The best traffic systems in Sim City minimized intersections just as much as -- if not more than -- throughput and mean travel distance.
https://www.youtube.com/playlist?list=PLEGCF-WLh2RJBqmxvZ0_i...
It seems to me that the average transit time is the wrong metric to optimize for.
Anyone know what those conditions are, offhand?
I actually believe that Waze has contributed to a lot of urban traffic problems as of late, because it ensures that more people contribute to braess' paradox instances that might have gone unrealized in the past.