Google maps, and other similar routing apps, should offer a no left turn option!
No, that 35 mile drive down twisty single track country lane with occasional passing spots will not save any time over the 40 mile motorway. Even if the road is _technically_ 60mph, you'll never reach that speed unless you're on a motorbike...
I think map apps should be optimizing for something more complex, like least amount of directions within a five minute arrival window. Saving two minutes of driving time isn't worth having to make eight more turns.
Google maps has sent me on some really werid routes with endless turns left, right right left right right right left left right left etc etc vs just staying on a main road with only one or two turns for only an extra couple of minutes minutes more
I'd be more than happy to stay on the easy main roads and turn once or twice rather than hack through the backstreets just to save <5% distance/time
Before I switched, I found Google maps really liked to have you turn left one street early, then turn right then turn left. I guess it was trying to eliminate the delay from the left turn at the busier intersection. It was pretty much always worse.
One issue is, as you say, that shortest-path routing can overload individual roads. There is an interesting and related concept in theoretical CS: oblivious routing. Instead of solving “What is the shortest route to my target?” locally, you try to determine a selection of routes that, if followed by every participant, minimise congestion (the maximum amount of vehicles over any road, relative to its capacity). Surprisingly, it is always possible to determine such routes, even if they are not allowed to depend on traffic conditions (how many vehicles try to go from A to B, how many from C to D, etc) ― this is what the “oblivious” refers to.
Of course, that does not solve the problem of route complexity.
99% of the time I wouldn't use it. But the 1% of the time that I'm doing something stupid the last thing I need is a extraneous hard intersections.
It's not like Google doesn't have the location data to figure out the difference between intersections where traffic is slow and steady vs where people routinely get stuck.