[HN Gopher] Traffic Simulator
___________________________________________________________________
Traffic Simulator
Author : eecc
Score : 391 points
Date : 2021-01-07 10:08 UTC (12 hours ago)
(HTM) web link (traffic-simulation.de)
(TXT) w3m dump (traffic-simulation.de)
| parhaml wrote:
| What is the source of the logic for these mechanics? Meaning, how
| did you model the results of these inputs? Traffic phenomena is
| really interesting to me. This is a great way to present these
| inputs and visually present the outcomes.
| acvny wrote:
| To model these types of processes people usually use stochastic
| processes (https://en.wikipedia.org/wiki/Stochastic_process). I
| don't know what the author used, but seems inaccurate.
| jeremiecoullon wrote:
| The author used the "intelligent driver model" (IDM):
| https://traffic-simulation.de/info/info_IDM.html
|
| It's a system of ODEs that describes the dynamics of each
| driver. So the inputs are: the parameters of the model and the
| inflow of cars in the section of road
| albertzeyer wrote:
| 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.
| Toutouxc wrote:
| BTW the M1 Macs run Cities Skylines beautifully through Rosetta
| 2. I lowkey wanted to try it for years and now on the M1 Air I
| can and the game is just amazing.
| brianjunyinchan wrote:
| Check out ABstreet as well on github:
|
| https://github.com/dabreegster/abstreet
| matkoniecz wrote:
| A/B Street is much, much more ambitious as far as traffic
| simulation goes, but still in progress.
|
| https://github.com/dabreegster/abstreet#ab-street
|
| If someone is looking for interesting Rust project to
| contribute (also as a beginner) I really recommend it. Author
| is great, friendly to PRs (what includes PRs made be
| programmers with no Rust experience).
| imaginenore wrote:
| That looks really cool! I hope they finish it.
| bstar77 wrote:
| City Skylines traffic simulation is mediocre at best. This
| project is extremely impressive. I sat and watched the traffic
| simulation for 15 minutes before I realized it.
| waiseristy wrote:
| 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
| sumtechguy wrote:
| Having watched way too many Biffa vids. The way to fix that
| is to create/force dedicated turning lanes. There is a plugin
| that lets you manage it. It should be built in. If you do not
| have the plugin sometimes you can fix it by changing the
| number of lanes on both sides of an interchange (what biffa
| calls lane mathematics). Basically if you have 3 lanes
| merging into 3 you need a 6 lane on the other side. If you
| have 6 and 3 dumping off you need 3 for both exits. That does
| not fix 4 way intersections though and usually you need the
| plugins to fix that.
| Shared404 wrote:
| I agree, Computer Science does suffer from many dumb computer
| tricks.
|
| Wait a second. Ah well, point still stands.
|
| E: It was a joke...
| airza wrote:
| In the first video a bunch of cars are crowded in one lane of
| the double lane road (a problem that plagues much of the
| traffic in the game)
| mbank wrote:
| Love these kind of micro simulations! They really help to
| discover non intuitive behaviour of complex systems just by
| playing around. Great job!
| Geminidog wrote:
| You don't need AI based non linear simulations to see what's
| going on. The simulation shows that traffic can be described in
| much simpler terms.
|
| You'll notice that traffic is actually a longitudinal wave that
| travels through the system. The cars are particles and traffic is
| crests in the wave.
|
| The wave usually travels backwards against the direction of the
| cars. The worst type of traffic is when you get a standing wave
| where the crest of the wave just stays in the same place.
|
| Take a look at the simulation with this knowledge in mind. Then
| you will actually see the wave.
|
| An elegant solution to alleviating traffic would be to then take
| techniques that dampen waves in materials and translate them into
| techniques that work for traffic.
| ishikawa wrote:
| This was first posted without https and with www in 2013.
| https://news.ycombinator.com/item?id=6756360
| timvdalen wrote:
| I saw a comment about this site earlier on a different thread,
| so I think someone dug it up because of that.
| fooyc wrote:
| 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...
| hedora wrote:
| Here's a more useful concept than induced demand:
|
| Ever since cities were invented, people have refused to have
| commutes longer than ~30 minutes each way, on average.
|
| The utility of the city increases with the number of people in
| the city.
|
| The purpose of the transit system (roads, trains, buses, bike
| lanes, side walks, ferries, etc., etc) is to increase the
| usefulness of the city by increasing the number of people that
| can commute to the city.
|
| If adding more roads, trains, etc leads to more commuters, that
| means the city is bottlenecked on the transit system, and you
| need to expand it even more.
|
| The core argument of induced demand is that more roads won't
| make your commute shorter. This observation shouldn't be
| surprising, since commute times are a function of humans
| tolerance for long commutes, and have been mostly constant for
| > 3000 years.
| throwaway0a5e wrote:
| "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 some water in it
| until it all makes its way through the pipe. But you have to be
| insane to use that as an argument against making the pipe
| bigger. Increasing the max capacity of the pipe (so more lanes,
| in the case of highways) means that it can have normal flow
| before it starts backing up. The "induces" demand because at
| the margins some people who were voluntarily changing their
| usage times to avoid the peak hours will commute at peak hours.
|
| I am intentionally trying to use generic language here because
| this isn't a unique phenomenon to highways.
| scatters wrote:
| 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.
| throwaway0a5e wrote:
| Why is more utilization a problem? It means more people are
| being served by infrastructure. Imagine complaining that
| more people are going to parks because the city turned a
| bunch of vacant lots into parks.
|
| In the case of things like roads, rails and bus stops more
| utilization means more economic activity which is a good
| thing.
| asdff wrote:
| 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.
| beerandt wrote:
| 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.
| leetcrew wrote:
| most of the surface streets you would want to widen can't
| be. you would have to take over property or (gasp!)
| remove parking.
| beerandt wrote:
| Improving capacity and traffic flow doesn't always have
| to mean widen.
|
| But the point is that you increase capacities where you
| can, and that it's better to start large with freeways,
| etc and work your way down, even if freeway capacity then
| exceeds feeder capacity (which then exceeds collector
| capacity, exceeds surface capacity).
| imtringued wrote:
| The problem with individual cars is that they are less
| efficient than public transport. If you make a city car
| friendly you are going to see more inefficient cars fill up
| the existing road. The problem isn't some induced demand
| meme. It's that some forms of transportation are inherently
| more inefficient than others. You can solve traffic problems
| by increasing lanes if you dedicate those additional lanes to
| public transport.
| jschwartzi wrote:
| 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.
| 99_00 wrote:
| Traffic isn't the primary problem. It is a side effect of
| mobility, which is desirable.
|
| If Traffic was the primary problem then the solution would be
| to eliminate roads.
| Daho0n wrote:
| Any games out there with good traffic simulation (IE. that
| doesn't break down as soon as there's a lot of traffic like
| Cities Skyline)?
| searedsteak wrote:
| Looks like maxing out acceleration solves all other problems. I
| guess we should require a minimum power-to-weight ratio for cars
| from now on.
| yabones wrote:
| Maxing out 'politeness', 'acceleration', and 'inflow' I could
| achieve nearly 7000veh/hr.
|
| Probably impossible, since it would cause heaps of rear ending
| accidents. Maybe if driver assist features both prevent lane
| changes and optimize avg. speed.
| kharak wrote:
| I've made the same observation. But I don't believe human
| drivers could reasonably take advantage of high acceleration,
| at least not as well as the simulated cars here. This is a
| great showcase of the usefulness of autonomous cars, though.
| Take humans out of the equation and traffic will flow.
| andrewstuart2 wrote:
| The other thing that really seems to make the biggest
| difference (in combination with better acceleration) is
| following distance, which is another thing that presumably
| gets less important with autonomous cars because you don't
| really have to account for a relatively slow reaction time or
| poor braking.
|
| The observation on acceleration does make me wonder whether
| teaching proper merging etiquette better (reach freeway
| speeds before you're at the merge junction) would make a
| significant difference if properly followed.
| gnopgnip wrote:
| Autonomous cars still need to have adequate following
| distance. Without that one small problem turns into a 10+
| car pileup.
| Daho0n wrote:
| Autonomous cars would be in contact with the cars ahead
| so it would react to car 1 braking, not number 9. IMO we
| will see this years before we see actual autonomous cars,
| no matter what fever dreams Elon Musk have.
| epanchin wrote:
| How do autonomous cars deal with cheap or worn tyres? Is
| there still a lot of allowance for braking distance?
| throwaway0a5e wrote:
| A burnout at the beginning of every drive cycle would do
| wonders for calibration.
| bob1029 wrote:
| Or weather/road conditions. Reaction time is irrelevant
| if you happen to be driving over an
| irregular/wet/oily/sandy/etc section of roadway at the
| moment maximum braking force is demanded.
| shellfishgene wrote:
| This would actually be possible to implement with the general
| switch to electric cars...
| jschwartzi wrote:
| What about electric trucks? I set the veh/hr to max and then
| when I changed truck percentage to 14% I almost immediately
| stopped traffic at the onramp as the trucks inevitably don't
| have enough space to accelerate from the meter point.
| Especially if one of the cars cuts the truck off.
| Cthulhu_ wrote:
| In practice that would mean a lot more head/tail accidents,
| I've seen that happen plenty of times in traffic jams from
| over-eager drivers, sudden stops (either people trying to go
| too fast or not paying attention), etc.
| bhupy wrote:
| Easier to do with self driving cars, and can probably be
| attained with Level 3 autonomy.
| amcoastal wrote:
| Yeah, and there would be no reason to increase acceleration
| -- increasing the acceleration only aids in this project
| because it shortens the time when the car behind the
| stopped car in front of it can get up to speed. If the cars
| are all talking to each other -- they can all start
| accelerating at the exact same time and rate as soon as the
| light turns green etc.
| bhupy wrote:
| That's true only when every car is a self driving car. In
| the interim, if only a subset of cars is running Level 3
| autonomy, then including a quick acceleration into the
| adaptive cruise control is a good way to minimize these
| phantom traffic jams.
| andrewstuart2 wrote:
| There's also the frequent problem of split attention when
| you're accelerating like that. Often you may be trying to
| change lanes, and checking a mirror for an opening. Even
| without that kind of better communication, computers are
| just better at tracking multiple data points at once.
| InitialLastName wrote:
| Not to mention killing a lot more non-car road users who
| don't have access to the same acceleration.
| bones6 wrote:
| On the ring map, with default settings, just stopping traffic
| with the traffic light for a second produces the dreaded rubber-
| band effect propagating forever around the circle. Fun simulator!
| billfruit wrote:
| That behaviour is mesmerising to observe in the simulation.
| iamflimflam1 wrote:
| Turning the politeness down to zero really messes things up for
| everyone. There's a lesson in there somewhere...
| niea_11 wrote:
| I found that changing the politeness in either directions
| causes traffic jams. But I feel it happens faster if you
| decrease the value (but I'm not sure). Also it's best to set
| "timewrap" to 20 times to see the effects quickly.
| [deleted]
| mongol wrote:
| I would like to use a driving simulator to learn how to drive on
| the left side. Is there something like that? Good if I would rent
| a car on Ireland.
| dogline wrote:
| I've always wanted to program something like this. What are good
| references to simulation programming to handle this kind of use
| case?
| bob1029 wrote:
| If you want to build a large scale, real-time simulation with
| many participants, you might want to check out some paradigms
| being used in the game development arena. Particularly concepts
| like Unity's DOTS/ECS approach.
|
| Ultimately, the task is producing a good model of your domain
| and then organizing the data in such a way that you can quickly
| mutate a very large number of instances with each tick (if you
| are seeking real-time).
|
| If you are not seeking real-time, you could probably do
| whatever the hell you want.
| billfruit wrote:
| I was also looking to learn more about this. Discrete Event
| Simulation books may be of some help.
| mickallen wrote:
| This looks really cool! What's the tech stack?
| sandworm101 wrote:
| 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 pavement. The most
| efficient way to move large numbers of cars down a road is at
| 200mph with only inches between each car.
| recursive wrote:
| > they purport to show that slower more polite driving is more
| efficient
|
| Where are you seeing this?
| jonnycomputer wrote:
| In this instance, upping the politeness bar seems to reduce
| traffic ...
| recursive wrote:
| The comment I was responding to indicated the opposite.
| falcrist wrote:
| Adjusting it in either direction seems detrimental.
| jedberg wrote:
| That's because these simulations don't include inattentive
| drivers. They assume everyone behaves ideally.
|
| Normally all those things you said would result in accidents.
| If the simulators randomly added delays for cars braking or
| starting up, and then kept a death count, it would be more
| accurate...
| ravi-delia wrote:
| Hell screw the death count, just a graph of average commuting
| time becoming unbounded would be enough to get people on
| board.
| kevindong wrote:
| 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 a single
| digit number of cars would be able to go through per green
| light.
| kiliantics wrote:
| 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.
| dmurray wrote:
| You've never been stopped at a light where the queue was
| many multiples of the number of cars that could get through
| in one cycle?
| sandworm101 wrote:
| Or worse yet, they leave so much space that they don't
| trigger the sensors. That can mess with the traffic
| management scheme, sometimes preventing a light from _ever_
| changing.
| screye wrote:
| 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)
| TheGallopedHigh wrote:
| These type of models are done to death in traffic and other
| social models. Just look up "agent based modeling" and read
| to your heart's content
| vbtemp wrote:
| Things like this are cool. What I would be curious to see though,
| rather than setting global parameters (i.e., politeness), would
| be to have each agent have its own politeness score (as well as
| other attributes). Models like the one linked to here work as if
| each agent is a particle, rather than autonomous decision-maker
| adapting to their circumstances locked in long-term, iterated
| games with other anonymous drivers.
|
| This way, agents would adapt their attributes to maximize their
| own local advantage, and therefore could see how large scale
| trends develop. I've driven in many countries and regions within
| countries, and it's just wild how "driving cultures" vary so
| much. Some places the drivers are so polite to the point it
| really makes things dangerous, other places the drivers are
| vindictive (distinct from being aggressive driver). It would be
| interesting to model how driving cultures emerge.
|
| Edit: I guess the short story is I'm really curious why some
| places, like Bangkok driving is chaotic, dangerous, gridlocked,
| and no one adheres to traffic laws much or yields to pedestrians,
| but relatively devoid of road rage (and people will let you merge
| over if you need to). In DC, people carefully adhere to red
| lights, stop signs, pedestrians, etc but will go far, far out of
| their way to block you from changing lanes once they see your
| turn signal go on.
|
| Also, exploring the game theoretic (probably prisoner's dilemma?)
| aspects of tailgating and how that seriously depends on the
| driving culture. When someone tailgates, the tailgatee can slow
| down (everyone loses), speed up or move out of the way (tailgater
| wins/tailgatee loses), etc. If everyone slowed down when
| tailgated, there would be no benefit of tailgating; if enough
| people give in when tailgated, that keeps rewarding the behavior.
| Anyway, that would be something fun to explore in one of these
| traffic simulations.
| pc86 wrote:
| This would be a neat reinforcement learning project.
|
| > _Some places the drivers are so polite to the point it really
| makes things dangerous_
|
| I've known people like this, who will approach a 4-way
| intersection and stop even when they don't have a stop sign and
| the perpendicular street does.
| jeffhuys wrote:
| Participating in traffic all comes down to being as
| predictable as possible, I think.
| beerandt wrote:
| Yes, but in a way that's obvious to other drivers.
|
| Driving decisively is more important to overall safety than
| driving defensively.
| mattbk1 wrote:
| *and people on foot or bicycles
| SilasX wrote:
| Yep. I prefer the driving rule, "Don't be nice, be
| predictable."
|
| That is, don't deliberately be mean, but don't extend any
| courtesy where doing so would come at the cost of being
| predictable.
| parhamn wrote:
| > who will approach a 4-way intersection and stop even when
| they don't have a stop sign and the perpendicular street does
|
| Not the main point but I never liked how traffic signs aren't
| affirmative sometimes. In the case of the 4-way usually the
| stopping direction have a stop sign with a missing "All Way"
| sign below it. But thats not required in all jurisdictions.
| Nor is the non-stopping direction 100% sure their stop sign
| is still visible (shrubs, weather, etc) and can proceed at
| regular speed.
|
| I'm sure there are a ton of reasons for the way things are, I
| just think the outcome is you can't really ever be 100% sure
| what the correct thing to do is without slowing down and
| observing.
| macintux wrote:
| Speaking as someone who recently blew through a 4-way stop
| with other cars waiting, because the setting sun made it
| hard to see the stop sign, yeah, there are no shortage of
| human factors at play.
| asdff wrote:
| Stop signs are the shape they are so you can recognize them
| from the reverse for this purpose
| btowngar wrote:
| Hard to recognize them from the reverse when they're
| hidden behind a bush!
| vbtemp wrote:
| Places where I've seen it, people who have the right of way
| take that to mean they get to play "traffic cop". E.g., at a
| 4-way stop the "extra polite" person who gets there first,
| instead of going through the intersection first, waits and
| waves the person who does not have the right of way to go
| through first, which makes that person (and everyone else)
| confused, and then causes a lot of slowdown, frustration,
| etc. Of course only happens in certain locales, where it's
| part of the local driving culture.
| throwaway0a5e wrote:
| Or they slam on the brakes at the end of what should be a
| merging ramp or lane because the fore and aft distances to
| the other traffic that were good enough for the prior N
| people would be too close for them.
| Daho0n wrote:
| Well to be fair the distance most people feel fine with
| is not near what is safe.
| 2iP1zbR wrote:
| this has always bothered me.
|
| if you have the right of way, and you do not take the right
| of way, in most cases you are effectively disobeying
| traffic rules and disrupting the flow of traffic.
| jsrcout wrote:
| > Some places the drivers are so polite to the point it really
| makes things dangerous
|
| I live in a small town that has extra polite drivers. It was
| really confusing for a while. Eventually I realized that it was
| a practical response to the overall street layout, with a
| limited number of main streets, and different areas of town not
| being well connected. Stopping to let others cross improves the
| overall traffic flow - if no one did it, traffic would just be
| backed up for miles.
| bonestamp2 wrote:
| It would be cool to study things like politeness, top speed,
| acceleration, etc in different cities and then create traffic
| profiles that represent these cities and see what kind of
| tweaks can improve each one.
| darrennix wrote:
| Clearly we just need to make all cars accelerate at 4.0m/s and
| our traffic problems would've solved.
| throwaway0a5e wrote:
| Regardless of how I change the map layout, traffic in/out flow or
| truck/car ratio I seem to get the best results when I crank
| accel, speed and right bias for trucks to the max and lane-change
| threshold and following distance to the minimum.
|
| Which makes sense since those are basically the ideal conditions
| for reducing the number of obstructions low speed (merging,
| exiting, trucks on grade) traffic poses to higher speed traffic
| and reduces the effective road area of the obstruction.
| snarfy wrote:
| You can almost always fix the traffic by maxing out
| acceleration. Sadly, this vindicates my real world aggressive
| driving behavior.
| ripperdoc wrote:
| Probably you need to add the factor of accidents. Not only do
| they kill people, they are also the major reason for blocking
| traffic.
| throwaway0a5e wrote:
| Why is it sad if it turns out a subset of people are already
| behaving in a way that analysis indicates promotes better
| flow?
| t0astbread wrote:
| Because aggressive driving is dangerous? Perhaps aggressive
| driving also contributes negatively to the overall flow in
| the real world when not everyone drives equally aggressive
| (i.e. through extra lane switches caused). But I don't know
| much about traffic analysis so idk.
| xixixao wrote:
| Needs an American mode where people don't know they should stick
| to the right-most lane, unless passing.
| throwaway0a5e wrote:
| And a Connecticut mode where nobody uses the right lane to pass
| people who do that.
| analog31 wrote:
| To simulate my neighborhood, it needs some parked cars and
| trees that appear out of nowhere.
| NwtnsMthd wrote:
| Other uniquely American things:
|
| - Passing on the right
|
| - Taking an exit from the passing lane (cutting everyone off)
|
| - Couch in the middle of the highway
| C19is20 wrote:
| Just set 'Politeness', to zero: don't touch anything
| else.....Italy.
|
| *Things have got better year on year, though. I have f+r
| dashcams - rarely needed, nowadays. If anything, they do ensure
| I drive better.
| vegetablepotpie wrote:
| It seems that decreasing politeness increases lane changing
| behavior. The effect of reducing politeness is that people in the
| on ramp get in the highway quicker but the whole highway slows
| down.
| sokoloff wrote:
| 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.
| leetcrew wrote:
| 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.
| aj7 wrote:
| Appears to violate divJ + rhodot = 0.
| gfxgirl wrote:
| I don't know if "right bias" is enough to simulate my experience
| in traffic which includes trying to get in the fastest lane and
| also trying to get over to the exit for my exit. As well as when
| my exit is backed up a couple of miles but the lane I'm in is
| moving faster such that I have to block my lane to wait for an
| opening into the lanes that will exit.
| reallymental wrote:
| Perhaps these questions are appropriate for this post.
|
| I'm beginning to delve into this space and I've not managed to
| get any satisfactory answers to these questions, despite my
| month(s) long search.
|
| 1) How does one build a traffic (i.e state-space system),
| forgetting the visualization aspect of things ? Just generating
| sparse matrices, and adding elements to interact (add/subtract)
| from these matrices would be a great start! Any way to do this in
| a compiled language ?
|
| 2) Are there any libraries out there that help you simulate
| traffic in an existing network of roads, extracted from
| OpenStreetMaps perhaps?
| skrunch wrote:
| This doesn't exactly answer your question, but what I settled
| on during my dissertation (granted, that was a few years ago
| now) was SUMO: https://www.eclipse.org/sumo/
|
| IIRC you could import maps from from open street map, but I'm
| not sure if it has a "headless" mode, without all the
| visualisation.
| 2Gkashmiri wrote:
| having your route to office simulated with this would be
| super cool on osm
| adamjb wrote:
| On 2) there's Matsim and AequilibraE off the top of my head.
| dabreegster wrote:
| 1) There are different choices you can make about simulating
| individual agents or aggregate flows along roads. Assuming
| you're interested in the former, you can advance the simulation
| in discrete time-steps using approaches like the intelligent
| driver model mentioned in another thread. Chapter 4 of
| https://apps.cs.utexas.edu/tech_reports/reports/tr/TR-2157.p...
| is a different approach to the discrete time system that tries
| to handle complications that come up when applying to
| OpenStreetMap, like having a vehicle cross multiple roads and
| intersections in a single 0.1 second timestep, due to really
| short roads. If you're willing to throw away detailed movement
| (including acceleration and lane-changing), you can try a
| discrete-event approach, where you say "this vehicle enters one
| end of a road at time t, don't calculate anything for it until
| t + best_case_time_to_cross".
| https://dabreegster.github.io/abstreet/trafficsim/index.html
| has some ideas there.
|
| 2) Another option with much less detailed traffic simulation,
| but much more UI focus, is abstreet.org
| mlaretallack wrote:
| For 2, Eclipse Sumo allows import of a road network from
| openstreetmap.
| whalesalad wrote:
| My favorite observation is that you can move the 'politeness'
| slider all the way up - touch nothing else - and watch the world
| burn.
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