5 ms·

This is an understated problem. Google used to regularly take me through a route that involves a left turn in a major road and multiple crossings where cross t

This is an understated problem. Google used to regularly take me through a route that involves a left turn in a major road and multiple crossings where cross traffic won’t stop. Literally two blocks from the suggested left turn is a left turn arrow signal which also avoids the dangerous crossings. It’s both dangerous and anxiety inducing and doesn’t save time either.

viburnum 7y ago
I wish it had a “no left turns” feature like they have for avoiding tolls.
- andrepd 7y ago
  I wish cities had roundabouts instead of intersections, so that would not be a problem :)
  - avh02 7y ago
    They take space for anything at reasonable size I'd guess. Strangely enough though it's one of the few things I miss about the city I grew up in (Jeddah, Saudi Arabia) - lots of outdoor art and sculptures because they had lots of very large roundabouts (check Google images to see what I mean about the outdoor art).
    - RugnirViking 7y ago
      It absolubately can work, for a famous and oft-studied example see the city of Milton Keynes in the UK. Hundreds of roundabouts
    - viburnum 7y ago
      America cities have too many oversized streets and major intersections. Keep the streets small and you don't need as many intersections and you can invest more in the ones you have. This is what they do in the Netherlands.
      - vanadium 7y ago
        Wisconsin has become one giant series of roundabouts across the state over the past decade; they’re everywhere after new construction and being retrofitted whenever the opportunity arises. Sometimes 2 and 3 roundabouts connected at times.
  - roblabla 7y ago
    I hate roundabouts. I live in France, and we have them everywhere. They're a huge clusterfuck that does not win any time, and when misused can be a lot more dangerous than a properly planned intersection. Of all the accidents I've driven past on my daily drives, all of them happened on roundabouts. I hate them.
    - jrochkind1 7y ago
      > Of all the accidents I've driven past on my daily drives, all of them happened on roundabouts. In localities with few/no roundabouts, the vast majority of accidents still happen at intersections. Intersections of roads are the most prone to accidents (for fairly obvious reasons), with or without roundabouts. I believe there is research showing roundabouts are actually quite a bit safer in general, but it's possible it depends on various things. But anyway, accidents happen mostly where two roads intersect, either way.
      - ferzul 7y ago
        Roundabouts are great for cars, and awful for just about everyone else. People, bikes, buses, trucks: all face difficulty or death in their presence.
        bkor 7y ago
        > People, bikes, buses, trucks: all face difficulty or death in their presence. Roundabouts make my bicycle commute way faster. This in The Netherlands where we cycle a lot. Difficulty or death is entirely incorrect. Suggest to compare the designs across countries, maybe there's a huge difference in the design?
        stoobs 7y ago
        I think the issue comes when people try to circumvent the give-way priority - which gets worse when there are multiple lanes and multiple exits. It certainly seems to be a people problem rather than a roundabout deign issue from my experience? People trying to "beat" people out onto the roundabout rather than giving way, people not using proper lane discipline and squeezing/cutting into other lanes etc..
  - Spooky23 7y ago
    Roundabouts only work in the burbs. In cities, they are death traps for pedestrians and cyclists.
    - bmn__ 7y ago
      Nonsense. See video linked in https://news.ycombinator.com/item?id=8819614 https://news.ycombinator.com/item?id=8819614 starting at minute 3.
    - bkor 7y ago
      > In cities, they are death traps for pedestrians and cyclists. I haven't experienced that for the many roundabouts we have in The Netherlands. Throughput is higher (can easily be measured), plus waiting time is lower thanks to roundabouts. Not exactly sure what you mean with "burbs" though it doesn't matter as they're heavily used in cities here.
    - Finnucane 7y ago
      I ride my bike through rotaries (as we call them here in Mass.) all the time. It's not that hard. It is advisable to try to ride as fast as possible, but the key is to signal clearly all movements in and out of the lane and the circle.
  - usrusr 7y ago
    Roundabouts have the unfortunate property of smoothing throughput from a sequence of chunks and gaps to a constant dribble. That's fine on limited access roads with overpasses and parallel feeder roads for local traffic or where overall throughput is always low enough to still comfortably cut in from a lower rank junction. On everything in between (enough traffic to make turning difficult, but still having direct junctions with access roads) you are better off with the occasional traffic light that will as a side effect serve gaps to meet rank junctions downstream.
- magduf 7y ago
  The problem is that it would be mostly useless, because it'd be buried in a menu somewhere where you can't easily change it while driving. The avoiding tolls thing is absolutely terrible that way. Thankfully, they finally put in a new feature where it shows you alternate routes, with and without tolls, and tells you if they do or don't have tolls. It took years for this to come about even though I had requested it many times, and it's plainly obviously needed. But before this, it was all-or-nothing, and it wasn't easy to change on the fly, and having it on was bad because it would frequently try to route me onto an expensive toll lane even though there was zero time savings, but for other routes a toll road was absolutely necessary. They should have it weight left turns higher (as in worse) so that routes tend to avoid them. When I drive to work, I can take my normal exit, and only take right turns, or if I miss it, I can take the next exit, but there's a terrible left turn there with a very long light. Google Maps consistently says "1 minute longer" for this route: BS. It might be about the same if you happen to catch the light, otherwise it's 5 minutes longer. I feel like their algorithm really doesn't take this into account well.
eigenvector 7y ago
This problem baffles me because all that has to be done to correct it is increase the estimated time of arrival penalty for making an unprotected left turn so that the routing algorithm doesn't mistakenly think it's faster. Ditto for U-turns, which Google constantly suggests (rather than turning onto a side street and U-turning there or going around the block) even when they are impossible (median in the way), dangerous (high speed road) or illegal.
- craftinator 7y ago
  Just another area where rules based heuristic systems can outperform machine learning systems by not removing edge cases through over generalization.
- ferzul 7y ago
  That's weird. Google maps seems to prefer to direct me on a kilometres long detour than to take a simple u-turn into an empty driveway. They do seem to have rules about u-turns, they just don't make sense.
  - beobab 7y ago
    One time I had TomTom accidentally switch itself on in my bag on the floor, set to Homer Simpson's voice and trying to redirect me to home. As I got further and further away the "turn left here" and "turn right here" directions got more and more frequent, until eventually he just started repeating "turn around where possible" until I was able to find somewhere reasonable to stop and turn it off.

viburnum 7y ago

I wish it had a “no left turns” feature like they have for avoiding tolls.

andrepd 7y ago
I wish cities had roundabouts instead of intersections, so that would not be a problem :)
- avh02 7y ago
  They take space for anything at reasonable size I'd guess. Strangely enough though it's one of the few things I miss about the city I grew up in (Jeddah, Saudi Arabia) - lots of outdoor art and sculptures because they had lots of very large roundabouts (check Google images to see what I mean about the outdoor art).
  - RugnirViking 7y ago
    It absolubately can work, for a famous and oft-studied example see the city of Milton Keynes in the UK. Hundreds of roundabouts
  - viburnum 7y ago
    America cities have too many oversized streets and major intersections. Keep the streets small and you don't need as many intersections and you can invest more in the ones you have. This is what they do in the Netherlands.
    - vanadium 7y ago
      Wisconsin has become one giant series of roundabouts across the state over the past decade; they’re everywhere after new construction and being retrofitted whenever the opportunity arises. Sometimes 2 and 3 roundabouts connected at times.
- roblabla 7y ago
  I hate roundabouts. I live in France, and we have them everywhere. They're a huge clusterfuck that does not win any time, and when misused can be a lot more dangerous than a properly planned intersection. Of all the accidents I've driven past on my daily drives, all of them happened on roundabouts. I hate them.
  - jrochkind1 7y ago
    > Of all the accidents I've driven past on my daily drives, all of them happened on roundabouts. In localities with few/no roundabouts, the vast majority of accidents still happen at intersections. Intersections of roads are the most prone to accidents (for fairly obvious reasons), with or without roundabouts. I believe there is research showing roundabouts are actually quite a bit safer in general, but it's possible it depends on various things. But anyway, accidents happen mostly where two roads intersect, either way.
    - ferzul 7y ago
      Roundabouts are great for cars, and awful for just about everyone else. People, bikes, buses, trucks: all face difficulty or death in their presence.
      - bkor 7y ago
        > People, bikes, buses, trucks: all face difficulty or death in their presence. Roundabouts make my bicycle commute way faster. This in The Netherlands where we cycle a lot. Difficulty or death is entirely incorrect. Suggest to compare the designs across countries, maybe there's a huge difference in the design?
        stoobs 7y ago
        I think the issue comes when people try to circumvent the give-way priority - which gets worse when there are multiple lanes and multiple exits. It certainly seems to be a people problem rather than a roundabout deign issue from my experience? People trying to "beat" people out onto the roundabout rather than giving way, people not using proper lane discipline and squeezing/cutting into other lanes etc..
- Spooky23 7y ago
  Roundabouts only work in the burbs. In cities, they are death traps for pedestrians and cyclists.
  - bmn__ 7y ago
    Nonsense. See video linked in https://news.ycombinator.com/item?id=8819614 https://news.ycombinator.com/item?id=8819614 starting at minute 3.
  - bkor 7y ago
    > In cities, they are death traps for pedestrians and cyclists. I haven't experienced that for the many roundabouts we have in The Netherlands. Throughput is higher (can easily be measured), plus waiting time is lower thanks to roundabouts. Not exactly sure what you mean with "burbs" though it doesn't matter as they're heavily used in cities here.
  - Finnucane 7y ago
    I ride my bike through rotaries (as we call them here in Mass.) all the time. It's not that hard. It is advisable to try to ride as fast as possible, but the key is to signal clearly all movements in and out of the lane and the circle.
- usrusr 7y ago
  Roundabouts have the unfortunate property of smoothing throughput from a sequence of chunks and gaps to a constant dribble. That's fine on limited access roads with overpasses and parallel feeder roads for local traffic or where overall throughput is always low enough to still comfortably cut in from a lower rank junction. On everything in between (enough traffic to make turning difficult, but still having direct junctions with access roads) you are better off with the occasional traffic light that will as a side effect serve gaps to meet rank junctions downstream.
magduf 7y ago
The problem is that it would be mostly useless, because it'd be buried in a menu somewhere where you can't easily change it while driving. The avoiding tolls thing is absolutely terrible that way. Thankfully, they finally put in a new feature where it shows you alternate routes, with and without tolls, and tells you if they do or don't have tolls. It took years for this to come about even though I had requested it many times, and it's plainly obviously needed. But before this, it was all-or-nothing, and it wasn't easy to change on the fly, and having it on was bad because it would frequently try to route me onto an expensive toll lane even though there was zero time savings, but for other routes a toll road was absolutely necessary. They should have it weight left turns higher (as in worse) so that routes tend to avoid them. When I drive to work, I can take my normal exit, and only take right turns, or if I miss it, I can take the next exit, but there's a terrible left turn there with a very long light. Google Maps consistently says "1 minute longer" for this route: BS. It might be about the same if you happen to catch the light, otherwise it's 5 minutes longer. I feel like their algorithm really doesn't take this into account well.

eigenvector 7y ago

This problem baffles me because all that has to be done to correct it is increase the estimated time of arrival penalty for making an unprotected left turn so that the routing algorithm doesn't mistakenly think it's faster. Ditto for U-turns, which Google constantly suggests (rather than turning onto a side street and U-turning there or going around the block) even when they are impossible (median in the way), dangerous (high speed road) or illegal.

craftinator 7y ago
Just another area where rules based heuristic systems can outperform machine learning systems by not removing edge cases through over generalization.
ferzul 7y ago
That's weird. Google maps seems to prefer to direct me on a kilometres long detour than to take a simple u-turn into an empty driveway. They do seem to have rules about u-turns, they just don't make sense.
- beobab 7y ago
  One time I had TomTom accidentally switch itself on in my bag on the floor, set to Homer Simpson's voice and trying to redirect me to home. As I got further and further away the "turn left here" and "turn right here" directions got more and more frequent, until eventually he just started repeating "turn around where possible" until I was able to find somewhere reasonable to stop and turn it off.