Don't want to make a left turn?

[Marc Collins]

I have both a truck cargo route and a bus route in a city where in each (in two different places) the affected route diverts around a block rather than the expected carrying on straight and the vehicles making a left turn into the next street towards their next stop.

Even if I use a waypoint to try to correct the problem, the route will circle around making it even worse, while still avoiding the left turn (at a traffic light). Other AI are using the left turn lane and the traffic is otherwise normal. In the case of the cargo route, there is another cargo route that successfully makes the same left turn the affected route avoids. Removing the traffic light has no effect on this strange unnecessary re-routing.

In all my zillion hours of playing TF2, I have never experienced this, and suspect it therefore may be related to the recent update. But wondering if anyone else has ever seen this behaviour?

The map is one that was started prior to the update, though on the surface seems to have made the transition without any issues, including several mods. It is also a huge map (1:2) if that might make a difference.

[paul.cockburn]

At the junction, are there roads of different widths? I've seen some weird behaviour around junctions like that.

[lozacenz]

if a road has multiple lanes, those lanes will have specific directions that vehicles in them can go at an intersection.

In a three lane (per direction) road, cars turning into the road from the left will go into the left hand lane, and from the left hand lane can only turn left, the right hand lane the same for the right, and the centre lane for straight through (it gets a bit weirder if there are four directions the traffic can go, or with two lane roads, but that's the basic logic).

If there's a node in between the two intersections, thus breaking the road into two sections, cars will change lanes at that node. Nodes happen automatically every so often, as well as at the start and end of any section you build, and at intersections (and they don't go away if you delete the other road that caused the intersection to exist)

Basically, your problem is caused by the intersections being too close together, so the vehicle has no opportunity (or at least not enough opportunities if it needs to change lanes more than once) to get into the correct lane before the point where it wants to turn off, so takes a different path instead.

(roads in Cities:Skylines also work like this, except that Cities:Skylines allows cars to turn Into whatever lane is convenient at intersections, while Transport Fever 2 does not.)

Note that bus lanes work for both buses and trucks (and also any cars that have no suitable alternative route to their destination), and that trucks and busses In the bus lane ignore the other lanes and treat the road as having only two lanes, allowing them to turn in any direction at intersections (but not allowing you to have them follow routes that don't get in each others' way, block stops, etc.)

[Vimpster]

That you have played a zillion hours and only just noticed this is quite remarkable. It has worked this way since the beginning.

As lozacenz said, vehicles can only change lanes where segments of a road break, and lanes have dedicated directions vehicles can travel. So if the blocks between intersections consists of only a single road segment then no lane changes are possible and the vehicles are forced to go in whatever direction the lane they are in dictates.

[RadiKyle]

Originally posted by Marc Collins:

The map is one that was started prior to the update, though on the surface seems to have made the transition without any issues, including several mods. It is also a huge map (1:2) if that might make a difference.

Were these routes working ok before the game update? Or do you mean they are new ones you made after the update?

Adding to the others, when there is not enough distance between a bus/truck stop and the intersection for vehicles to change lanes, I insert a node using this splitter mod:
https://steamcommunity.com/sharedfiles/filedetails/?id=2761086439
(Note it's dependent on a marker mod, you need to install both.) Works very easy, just select the road segment with the marker tool, then divide it with the splitter tool.

Cheers

[Marc Collins]

Thanks all for the replies. The areas where this is happening are indeed dense urban areas with closely spaced blocks/intersections, so the explanation about the nodes is plausible. I guess it is just coincidence that I have not yet until now placed stops in a way that triggers the issue.

Of course, the whole path-finding/lane selection process is quite poor in this game, so perhaps if that core issue was improved thoroughly as is needed, scenarios like this would no longer occur.

[ronelst85]

My answer is that the path finding and especially the lane usage are atrocious in this game. One of the reasons I barely use road vehicles.

[Vimpster]

Although there are certain cases where path finding is not optimal, such as zigzagging through a town rather than minimising the number of turns, when it comes to lane changes and left turns on 4 and 6 lane roads, there is no path finding change that would resolve that. There are simply rules that prevent the pathing algorithm from choosing certain paths.

They did give us control of which lane a vehicle will use via the waypoint tool not too long ago. But again they still can't use the waypoint to access a lane that is physically unreachable.

[Marc Collins]

Originally posted by Vimpster:

Although there are certain cases where path finding is not optimal, such as zigzagging through a town rather than minimising the number of turns, when it comes to lane changes and left turns on 4 and 6 lane roads, there is no path finding change that would resolve that. There are simply rules that prevent the pathing algorithm from choosing certain paths.

They did give us control of which lane a vehicle will use via the waypoint tool not too long ago. But again they still can't use the waypoint to access a lane that is physically unreachable.

How can you specify a lane with the waypoint tool? I tried this for other situations not involving the node bug, but it didn't seem to work intuitively. Or, I am just dumb.

[lozacenz]

Originally posted by Marc Collins:

Originally posted by Vimpster:

Although there are certain cases where path finding is not optimal, such as zigzagging through a town rather than minimising the number of turns, when it comes to lane changes and left turns on 4 and 6 lane roads, there is no path finding change that would resolve that. There are simply rules that prevent the pathing algorithm from choosing certain paths.

They did give us control of which lane a vehicle will use via the waypoint tool not too long ago. But again they still can't use the waypoint to access a lane that is physically unreachable.

How can you specify a lane with the waypoint tool? I tried this for other situations not involving the node bug, but it didn't seem to work intuitively. Or, I am just dumb.

It wasn't always possible, it was in one of the more recent (as such things go) updates. Way points are effectively stations (kind of), and for roads they can set 'lanes' the same way a station would set 'terminals'.

Basically, click the waypoint and change which lane routes passing through it use the same way you would change which platform a train would use at a train station.