Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Traffic Simulator

traffic-simulation.de

Post reply on HN
Print view View original

71–80 of 143 posts

Re: Traffic Simulator

#71

Post by jschwartzi »

throwaway0a5e wrote: post #54
fooyc wrote: post #45

The more lanes you add, the more cars you get. Adding more lanes doesn't solve traffic issues. https://en.wikipedia.org/wiki/Induced_demand#Induced_traffic...

"Induced demand" is just a backhanded way of complaining that more people can be served by expansion of a particular piece of infrastructure that you don't like. Nobody ever complains about induced demand on the subway from more frequent service causing more people to decide that's the best option for them. Rush hour is like pouring a 5gal bucket into a sink. You can't reasonably handle that all at once will have som…

No, Induced Demand describes the phenomenon whereby the roads eat considerably into the surrounding neighborhoods and get louder and more dangerous while the amount of traffic remains the same.

Re: Traffic Simulator

#72

Post by falcrist »

jonnycomputer wrote: post #66
recursive wrote: post #62

Earlier quoted context omitted.

> they purport to show that slower more polite driving is more efficient Where are you seeing this?

In this instance, upping the politeness bar seems to reduce traffic ...

Adjusting it in either direction seems detrimental.

Re: Traffic Simulator

#73

Post by beerandt »

asdff wrote: post #64
throwaway0a5e wrote: post #54

Earlier quoted context omitted.

"Induced demand" is just a backhanded way of complaining that more people can be served by expansion of a particular piece of infrastructure that you don't like. Nobody ever complains about induced demand on the subway from more frequent service causing more people to decide that's the best option for them. Rush hour is like pouring a 5gal bucket into a sink. You can't reasonably handle that all at once will have som…

The issue with widening highways is that traffic doesn't exist in a vacuum. You aren't widening the surface roads that back up into the highway or the interchanges to other highways, that is the crux of traffic. You widen one pipe but it feeds into the same set of narrow straws anyway, and your sink is just as backed up.

Still, this is an argument for upgrading all "pipes", not one for attempting to control demand on the supply/capacity side.

But even absent that, you want surface, collector, and feeder streets to be the natural "rate-limiting" parts of the network (in that order).

It's why it's especially egregious to wave-in people from a driveway or parking lot into traffic on an already congested street. It breaks the natural rate limiting.

The right-of-way rules are surprisingly well-thought out, from a systems perspective.

Re: Traffic Simulator

#74

Post by sokoloff »

Any idea why the max Accel figure is set so low by default? 0.3 m/s/s requires over a minute and a half to accelerate to 60 mph/100kph.

I'd expect something more like 2 m/s/s (0-100 kph in 14 seconds) if it's a safety-related threshold and at least 1 m/s/s if it's a general operation setting.

That it's set so far away from that makes me wonder if I don't understand what it's used for.

Re: Traffic Simulator

#75

Post by scatters »

throwaway0a5e wrote: post #54
fooyc wrote: post #45

The more lanes you add, the more cars you get. Adding more lanes doesn't solve traffic issues. https://en.wikipedia.org/wiki/Induced_demand#Induced_traffic...

"Induced demand" is just a backhanded way of complaining that more people can be served by expansion of a particular piece of infrastructure that you don't like. Nobody ever complains about induced demand on the subway from more frequent service causing more people to decide that's the best option for them. Rush hour is like pouring a 5gal bucket into a sink. You can't reasonably handle that all at once will have som…

More frequent service on the subway doesn't require vast amounts of land to be removed from productive activity. At most it might require a small expansion of stabling facilities for extra carriages and engines.

Induced demand means that when you make the drain pipe bigger, the bucket gets bigger as well, so the sink gets even more full. This is not sustainable.

Re: Traffic Simulator

#76

Post by waiseristy »

albertzeyer wrote: post #51

Cities Skylines is very nice for such traffic simulations. https://www.youtube.com/watch?v=yITr127KZtQ ( https://news.ycombinator.com/item?id=17182008 ) ( https://www.reddit.com/r/CitiesSkylines/comments/7h6zr0/traf... ) https://www.youtube.com/c/BiffaPlaysIndie/search?query=lane+... This is frequently posted here on HN. E.g. https://news.ycombinator.com/item?id=25632642 .

Unfortunately CS suffers from many "dumb computer tricks". The pathing algorithm is open loop, often causing huge 1 lane jams even though it would be more efficient for through traffic to use other less congested lanes. You end up needing to create crazy unrealistic spaghetti interchanges in order to trick the AI into behaving

Re: Traffic Simulator

#77

Post by screye »

sandworm101 wrote: post #56

I love these little simulators because while they purport to show that slower more polite driving is more efficient, more often than not they show the exact opposite. Want to shove the most cars through per hour? Remove the speed limit. Accelerate and brake like every intersection is a drag race. Leave absolutely no distance between cars. And dump any notion of polite lane changes. NASCAR was right: Minimize unused p…

One solution might be to characterize individual drivers (agents) by running an RL experiment that mimics the interactions of individual car drivers. If the reward function is made to compare traffic patterns of the simulation vs real life, then eventually the RL model (a combination of agents) should converge to how humans drive.

So you would have various transition probabilities of a car driver moving from an attentive state into various inattentive states, with drivers having different reactions in each state.

It would also help to have a level of "variance" in individual drivers. So instead of having a bunch of drivers who are just as likely to make mistakes, you have some who transition far more easily into inattentiveness and some whose likelihood of damage/nuisance is higher than the standard driver when inattentive.

It seems entirely doable. (famous last words)

Re: Traffic Simulator

#78

Post by leetcrew »

sokoloff wrote: post #74

Any idea why the max Accel figure is set so low by default? 0.3 m/s/s requires over a minute and a half to accelerate to 60 mph/100kph. I'd expect something more like 2 m/s/s (0-100 kph in 14 seconds) if it's a safety-related threshold and at least 1 m/s/s if it's a general operation setting. That it's set so far away from that makes me wonder if I don't understand what it's used for.

it is odd, especially since the "info" section on the same page lists reasonable figures as being in the range of 0.8-2.5 m/s/s. even 0.8 makes a big difference over 0.3. I can only assume they set the initial conditions to actually result in a traffic jam.

Re: Traffic Simulator

#79

Post by leetcrew »

beerandt wrote: post #73
asdff wrote: post #64

Earlier quoted context omitted.

The issue with widening highways is that traffic doesn't exist in a vacuum. You aren't widening the surface roads that back up into the highway or the interchanges to other highways, that is the crux of traffic. You widen one pipe but it feeds into the same set of narrow straws anyway, and your sink is just as backed up.

Still, this is an argument for upgrading all "pipes", not one for attempting to control demand on the supply/capacity side. But even absent that, you want surface, collector, and feeder streets to be the natural "rate-limiting" parts of the network (in that order). It's why it's especially egregious to wave-in people from a driveway or parking lot into traffic on an already congested street. It breaks the natural rat…

most of the surface streets you would want to widen can't be. you would have to take over property or (gasp!) remove parking.

Re: Traffic Simulator

#80

Post by kiliantics »

kevindong wrote: post #65
sandworm101 wrote: post #56

I love these little simulators because while they purport to show that slower more polite driving is more efficient, more often than not they show the exact opposite. Want to shove the most cars through per hour? Remove the speed limit. Accelerate and brake like every intersection is a drag race. Leave absolutely no distance between cars. And dump any notion of polite lane changes. NASCAR was right: Minimize unused p…

A pet peeve of mine when I still drove was when drivers would leave 1-3 car length's in front of their car when stopped at a stoplight. And then after the car in front starts moving, it'd take them a solid second to start inching forward also. The bigger problem was that this type of behavior was the norm to the point where at slow speed intersections with stoplights (e.g. city streets around college campuses), only…

Putting more people through per stoplight doesn't really change much. You just get more people at the next stop light. The light is by far the limiting factor, not the drivers. That's why polite driving actually helps, because you get less people blocking each other and less mishaps, the things that actually slow everything down.
Post reply on HN