Why aren't navigation apps smart enough not to try to make me turn left from a side street onto a busy four-lane road?

A similar problem I’ve encountered is being directed to enter a freeway on a left side ramp and take the next exit on the right with virtually no space to cross all the lanes and that’s assuming that magically there is no traffic (which you can be assured is very heavy). On that route the first time I took a direct, main road route which was quick and simple. The next time I decided to try the GPS unit’s way, uh-oh. Then the other way the next times.

A also suspect that there is a fair amount of confirmation type bias that goes into the perception of the users. Suppose it takes 2 minutes of waiting to turn left off a side street, but it takes one minute to extend the drive to a street with a light and another minute and a half waiting at the light. Statistically the first route is better because it takes 30 seconds less, but that 2 minutes waiting for a left turn is spent in frustration and mild anxiety so it seems longer than a more relaxed time waiting for the light at a controlled intersection. The apps are designed to minimize time not anxiety.

This. I wish there was a setting where it wouldn’t give the fastest route that only saves me 2-3 minutes but requires multiple turns onto poorly marked streets.

And here I am with the opposite issue: Google Maps always tells me to turn right at the T intersection by my house and then do a U-turn instead of just turning left at the light, which has been there for over 25 years. Why? No idea.

From my mapping days I recall road segments in the data base were coded according to what type of road it is, which also figured-in the potential speed one could travel:

  • 1-Freeway with only separated grade access (generally, interstates)
  • 2-Highway with separated and at-grade access (generally, US and State highways)
  • 3-Arterial surface road (County road, major road with connections to highways and freeways)
  • 4-Collector street (connecting neighborhoods to arterials)
  • 5-Neighborhood street

Of course, there are a myriad of exceptions out there, which is why we went out with big printouts and drove all the streets to capture what was really going on at ground level and update the map data base - for example in CA there are state highways that are freeways.

Anyway, the map data base may recognize the main road in the OP as an arterial, but unless it is split by a physical median in the data base (two separate line segments going one-way in opposite directions), the logic will assume a left turn is possible from the side road and just go ahead and offer that. If there is a signed “No Left Turn” then that should have been captured in the data base. If the driver finds that suggestion too dangerous or not viable for some reason, you can always just drive another way and let the software re-calculate your route, as mentioned.

The map data bases these days may very well capture the number of lanes on a road and take that into consideration, or the map-makers can just add a left turn restriction at the OP’s intersection, but it’s still up to the driver to make decisions on safety.

Definitely so.

I typically simultaneously run Waze or Google Map on my phone and the Tesla nav on its screen. I glance at them both to get their opinions, but I frequently ignore them. So their dumb suggestions are quickly forgotten. While the discovery of an alt route that just happens to be working this very moment is remembered.


My problem with Apple Map is that their display choices are terrible. There no visual distinction between low traffic conditions and missing traffic data; this is the app-killer. The names of streets are hard to read and can’t be easily zoomed in. The area it shows does not always follow the route. For example, let’s say my trip is to a destination in the east. But I need to head west before getting on the freeway. It will show an area towards east that doesn’t include my route.

I think the issue is that assuming the left turn is possible, it doesn’t really have a good handle on calculating how long you’ll sit there before you can actually turn left due to how heavy the traffic is. So it’ll direct you that way, even though other routes may actually be faster because of the wait time.

I wish there was more customization available; things like “avoid residential streets”, or a “find the least aggravating route within X minutes of the fastest one”. I’m not so stuck on getting there the very earliest I can, if it involves rush hour and major freeway interchanges, road construction, etc… I’d rather add a few minutes and have a more pleasant drive.

I did think of that possibility, but after looking at the Waze map editor, and seeing that it apparently doesn’t have data on what kind of intersection each intersection is (i.e., traffic signal, stop sign, etc.) and the data on the number of lanes is wrong, I don’t think it’s taking those factors into account. It simply doesn’t have enough information to say “that left turn would probably take a long time to make, because the street the driver is turning from is a small side street, and the street he’s turning onto is a main arterial road, and traffic on that main arterial road is heavy in both directions right now, and the driver doesn’t have a traffic signal, just a stop sign in his direction only; traffic on the main arterial road doesn’t have to stop.”

I think so too. It knows that traffic on the main road is currently traveling at an average speed of 37 mph, and that traffic on the side street is currently traveling an average speed of 15 mph, so if your route has you traveling 1/2 mile on the side street and then 1 mile on the main street, it just figures that’s going to take you 3.6 minutes. It doesn’t take the turn into account.

It’s interesting that several replies in this thread seem to think I’m talking about an intersection where the turn is impossible, i.e., it’s not allowed, or there’s a concrete median or something. I thought it was a pretty clear in the OP that I’m talking about a turn that’s allowed and would be perfectly reasonable if traffic was light, but practically impossible when traffic is heavy because there is no break in traffic long enough to make the turn.

I have had map programs do silly things often. Once after the freeway off ramp it wanted me to make a left turn onto a dead end street.

Yeah I think the navi apps are not that smart. Even if they are leveraging crowd-sourced, real-time traffic conditions showing heavy traffic on the main road, there is probably not enough data for the program to determine practicality of a left turn from the side road at a certain time, or having to cross multiple lanes in a short distance. The data base can only use the data it has available, and as long as the side road segment connects to the main road, and no restrictions are captured in the data, it will allow the left turn to be included (blind to real-world conditions).

Perhaps the apps can be enhanced with additional restriction options for avoiding left turns in general, or logic to estimate waiting time at intersections for specific maneuvers with real-time data input, but it appears they are not there yet, or the makers of the apps think it’s not worth the time to develop such logic.

While we would call a constant stream of cars “heavy traffic”, don’t the apps measure how heavy the traffic is through the average traffic speed? So, if the constant stream of cars past the side street intersection is moving at the speed limit, it won’t ever show up as “heavy” in the app.

It’s because in the end, it’s people that enter the data (in one way or another) I’m frankly surprised routing apps are as good as they are.

You have no idea how happy you’ve made me today.

Apple Maps does this, depending on the route. It’s not a setting, though, it’s just one of the route suggestions that shows up called “fewer turns.” I haven’t used Google Maps frequently enough to remember seeing it do the same, but I’d imagine it does.

To a certain extent, but Waze has this concept called “traffic jam” that I believe is separate from that, the result of users explicitly using the app to report a traffic jam. You can initiate this report yourself, or Waze will sometimes prompt you for it if it detects that you’re moving much slower than it expects you to move. There are three levels of severity: Moderate, Heavy, and Standstill. These “traffic jams” then show up on the map.

Also, you would think that if it had enough users on the road in a certain period of time, it could factor in how many cars go by per minute, as opposed to just their average speed.

ISTM just knowing the type of intersection (traffic signal vs. stop sign, and if the latter, in which directions) would go a long way. It’s kind of surprising that’s apparently still not part of the map data.

We recently battled with Google maps that wanted us to backtrack to a freeway. To get on that freeway, and go for a grand total of one exit. And then go back up to where we were nearly at. And it wasn’t hard to get to that location from where we were. A lot less driving than going back to the freeway.

My wife was the navigator and I wasn’t happy with the directions and I refused to take them. I’m guessing these map apps lead to many divorces.

And to the OP, yes, they give shit directions often.

Edit to add: We are still married, but that is tenuous based on the amount of car travel we have coming up. Maybe I should get a postnup signed?

That’s the thing with these navi apps since they came on the market - if you already know where you are going and how to get there, they wont be much help, and will never be able to pick a route “better” than yours.

If you are going someplace where you are not familiar, they can be handy.

That’s certainly true for offline navigation. For online navigation the app is better than me in one important way. The app knows about traffic conditions that I can’t see. For example, there is a major slowdown on the direct route, so an alternative route should be taken. Or even the next level of that, the direct route is congested, so a number of people have shifted to the alternative route, meaning both routes take about the same amount of time.

Well, the thing about apps like Waze is they can tell you real-time information you don’t know… Like there’s an accident ahead that will add twenty minutes to your trip, let’s route you around that. Very handy for regular commuters. Though the other day heading to my son’s daycare, I have no idea where that thing took me. I got there twenty minutes faster than my usual route, so I don’t exactly regret it, but I was way out of my element. My only real gripe is that this feature doesn’t include an explanation of why you’re being given these specific directions - sometimes it’s a preferred route because it saves 2 minutes, and sometimes it’s because of a major accident or delay.

Oh, I agree real-time traffic info taken into consideration is better, and an explainer would go a long way in preventing someone from over-riding the suggested routing because they “know a better route.”