Traffic Simulation
traffic-simulation.de
traffic-simulation.de
Back where he used to live at some point road authorities increased speed limits and found that average speed decreased. His explanation was simple: once speed limits matched drivers expectations they started to respect them. (Other explanations that I can pull from thin air now is police promising that the new limits will be enforced a lot less leniently than the old, or that speeds went down because of saturation congestion.)
[0]: although unconfirmed for me IIRC, maybe someone here can tell me were to find data
Instead we have limits based on polices very much separate from road conditions or actual traffic patterns. School zones are 30kph not because that's the 85th percentile but because that's the law. US highways were once capped at 55mph to save on gas during the fuel crisis (see 1974 Emergency Highway Energy Conservation Act). That certainly had nothing to do with traffic patterns. If 85% was a thing, I wouldn't cross a bridge every day signed for 50kph but where not a single vehicle is below 80 and the cops say nothing until you're over 100.
A good example happened near my home recently. A road that connects a small town (population 8,000) to a larger town (population 40,000) was the subject of quite a lot of debate. The road is a rural two lane roadway that sees about 10,000 vehicles per day. Speed studies were performed by three different groups (the small city, the large city, and the State Department of Transportation). Each of the groups determined their own speed limit recommendation, each was different. Ultimately, the State had final say on the matter and split the difference between the three recommendations. The State had originally wanted the highest speed limit of the three. The two towns wanted lower speed limits citing safety concerns and a desire to force alternate routes that would take traffic through areas with better infrastructure for the traffic load.
I do credit this particular simulation for modeling acceleration/deceleration. Playing around with it leads to the conclusion that many congestion problems can be addressed by increasing the performance numbers for cars, and by encouraging people to use their brakes/engines to their full potential. We should all drive as if in nascar, minimizing gaps to fully utilize the available road. Clarkson would be proud.
I would like to see a simulation of cars+trucks+motorcyles. Two-wheeled vehicles are common everywhere and in some countries are dominant on the roads, yet they are never included in these models. And toss in a few bicycles just for kicks.
Realworld "simulation": https://www.youtube.com/watch?v=7wm-pZp_mi0
Normal drivers, unaware of the above, will generally also stop and go slowly in traffic jams.
My personal pet peeve is when there is a reason for a slowdown (emergency vehicle, crash, etc) and drivers slow down further to look at it, unaware that they're are then currently causing the jam they just waited in.
I do remember an assignment that was modeling multiple different traffic flow models. The thing that stood out to me is how after a long time span with an network that was stuck with the same vehicles, like this model, traffic flow issues tended to become exaggerated.
As a traffic engineer, I use a product called Vissim to do exactly this kind of thing for real world scenarios. Very fun stuff.
Now add an option to import street layouts from OpenStreetMap...
Our town has implemented a few of these traffic circles. For some reason a memorial to the killed appears a few months each time after one is opened. I don't think it was drivers killed, I think it was pedestrians trying to cross at the inlets/outlets.
If you decrease the "comfortable deceleration" parameter all the way, you significantly increase the number of cars that can be handled without traffic jams.
Also, try turning T/s0/b all the way down, a all the way up, and then increase the density to about 75. Because the simulated drivers have very fast reaction times, the traffic oscillations propagate much faster than the cars are actually moving, creating some cool-looking spiral patterns.