Transforming OpenStreetMap into thick roads and intersections • Hacker News Board

Re: Transforming OpenStreetMap into thick roads and intersections

#31

Post by dabreegster » Sat, Sep 18, 2021, 2:25 PM UTC

Dylan16807 wrote: post #28

> Highway on/off ramps https://a-b-street.github.io/docs/tech/map/geometry/index.ht... It's hard to say which is better here, to be honest. A giant blob of gray is less helpful than showing some lanes, but the original version is much closer to the actual shape: https://www.google.com/maps/@47.6564275,-122.3223112,203m/da... Though apparently even google can't handle this intersection. Where did the middle layer of r…

Hmm, I guess I never checked satellite for that example. Part of the motivation there was improving the simulation. While vehicles are moving through the intersection, they grab a lock and prevent conflicting movements. A huge intersection takes longer to cross and was causing unrealistic backups here. But that was only because of the wacky lane-changing model (can only change between those 4 northbound lanes in an intersection, where conflicts are modeled) and poor lane placement at the time. Some of that's been fixed, worth revisiting the shape.

Re: Transforming OpenStreetMap into thick roads and intersections

#32

Post by dabreegster » Sat, Sep 18, 2021, 2:26 PM UTC

db48x wrote: post #29

Very cool. Unfortunately it looks like I managed to put it into an infinite loop in the tutorial. Or possibly I just didn’t wait long enough after saving my changes…

I haven't given any love to the poor tutorial mode in ages, so I'm not surprised you found a bug. Please file an issue (https://github.com/dabreegster/abstreet/issues) and describe how to reproduce the problem. If you can open the browser developer console (Ctrl+shift+I in firefox), often the last part will be really helpful.

Re: Transforming OpenStreetMap into thick roads and intersections

#33

Post by takk309 » Sat, Sep 18, 2021, 4:17 PM UTC

dabreegster wrote: post #18

takk309 wrote: post #12

I am a professional traffic engineer and I build micro-simulation models for most of the projects I am involved with. I can say that compared to software that is used in industry (PTV Vissim, PTV Vistro, and Trafficware Synchro) it looks like A/B is a reasonable toy model that can get pretty close to the real thing. I think it is great that software exists at a level for individuals without huge budgets to be able to…

Thank you for the industry insight! I'm definitely not trying to match the degree of realism and calibration with the professional stuff -- there's no way I could, without way more resources. A/B Street's simulation is more for visualization than getting meaningful results -- although I am quite proud of the dataviz we've baked in. From talking to planners, reaching for these tools is a huge time and money commitment…

At the end of the day better communication between the public, engineers, planners, and respective agencies is the goal. We have a joke that gets repeated all too often, everyone is a traffic engineer, just ask them! Rapid iteration is key to be able to look at all scenarios, no matter how crazy they may be.

Re: Transforming OpenStreetMap into thick roads and intersections

#34

Post by takk309 » Sat, Sep 18, 2021, 4:23 PM UTC

SECProto wrote: post #24

benrbray wrote: post #19

Earlier quoted context omitted.

Can you or any other traffic engineers here tell me why we find it acceptable that cars are allowed to make unprotected left turns while pedestrians have a walk signal? Right turn on red is bad enough, but unprotected lefts give drivers a direct incentive to torpedo into crossing cyclists / pedestrians, as slowing down would mean a collision with oncoming traffic! Too many intersections in downtown Atlanta, for insta…

Most North American road infrastructure has been rebuilt over the last century to be automobile-centric. "We" deem that conflict to be acceptable because the alternative is more complicated phasing - most of which results in delays to car traffic (and pedestrians!), and so most places won't accept it. For details, here's [1] a document that outlines the tradeoffs in various different signal phasing designs. TL;DR is…

I agree completely with this comment. Most places signal timing is done with the main scoring metric of reducing vehicle delay. Pedestrians are just an after thought that can be squeezed into a vehicle specific timing plan. As an example, how often do you see a pedestrian scramble, walk signals in all directions, outside of somewhere like Time Square?

Re: Transforming OpenStreetMap into thick roads and intersections

#35

Post by takk309 » Sat, Sep 18, 2021, 4:25 PM UTC

jerry1979 wrote: post #27

takk309 wrote: post #12

I am a professional traffic engineer and I build micro-simulation models for most of the projects I am involved with. I can say that compared to software that is used in industry (PTV Vissim, PTV Vistro, and Trafficware Synchro) it looks like A/B is a reasonable toy model that can get pretty close to the real thing. I think it is great that software exists at a level for individuals without huge budgets to be able to…

As someone with interest in traffic models, what spaces do you or your peers hang out outline?

That is a tough question because I can't think of any places really. Maybe look into the Institute of Traffic Engineers, they may have a forum of some sort.

Re: Transforming OpenStreetMap into thick roads and intersections

#36

Post by benrbray » Sat, Sep 18, 2021, 5:37 PM UTC

takk309 wrote: post #34

SECProto wrote: post #24

Earlier quoted context omitted.

Most North American road infrastructure has been rebuilt over the last century to be automobile-centric. "We" deem that conflict to be acceptable because the alternative is more complicated phasing - most of which results in delays to car traffic (and pedestrians!), and so most places won't accept it. For details, here's [1] a document that outlines the tradeoffs in various different signal phasing designs. TL;DR is…

I agree completely with this comment. Most places signal timing is done with the main scoring metric of reducing vehicle delay. Pedestrians are just an after thought that can be squeezed into a vehicle specific timing plan. As an example, how often do you see a pedestrian scramble, walk signals in all directions, outside of somewhere like Time Square?

Some of the problematic intersections in Atlanta have slowly been replaced with scrambles, and it's amazing as a pedestrian. I hope to see more and more of those!