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.

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.

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.

Just another area where rules based heuristic systems can outperform machine learning systems by not removing edge cases through over generalization.

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

I wish cities had roundabouts instead of intersections, so that would not be a problem :)

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.

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.

> 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.

Roundabouts are great for cars, and awful for just about everyone else. People, bikes, buses, trucks: all face difficulty or death in their presence.

> 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?

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..

You should copy the Dutch then. Their car+bike road designs are something else. Roundabouts included.

> They're a huge clusterfuck that does not win any time

Research shows the opposite. They can handle more traffic within a given timeframe. The bit about accidents seems strange. Not sure why you'd think that. I'm wondering if your roundabouts have some kind of design flaw.

Well, having driven on France on holidays, the problem seems to be with the driving culture. The roundabouts are very busy, and likely as a result drivers dart out in the shortest possible gaps in traffic. If you decide to play it safe, then the backed up traffic behind you starts honking at you, increasing the pressure and pushing you to make a bad decision. I found it very stressful indeed! (Perhaps all of France is not like this).

The Place Charles de Gaulle Étoile (Arc de Triomphe) in Paris is a gigantic roundabout, with the peculiar feature that traffic entering the system has priority ; traffic already on the roundabout must yield. This would lead to perpetual gridlock were there no traffic lights controlling access to the roundabout. This kind of junction used to be common in cities.

Out in the countryside roundabouts in France operate in the "normal" way : approaching traffic yields to traffic already in the system, with the usual triangular "yield" sign making priority clear.

It's possible that your experience of French roundabouts is related to driver confusion between these two systems.

The research I've seen suggest roundabouts do indeed cause accidents, but they're always low-speed accidents where people don't die. Intersections on the other hand are more likely to cause deaths because speeds can be much greater.

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).

It absolubately can work, for a famous and oft-studied example see the city of Milton Keynes in the UK. Hundreds of roundabouts

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.

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.

Roundabouts only work in the burbs. In cities, they are death traps for pedestrians and cyclists.

Nonsense. See video linked in https://news.ycombinator.com/item?id=8819614 starting at minute 3.

> 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.

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.

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.