Your problem could be a simple one. Ok example you don't allow buses to ignore lane arrows. You make road right turn only assuming your using right hand drive ok and only cars left lane can go straight. You place a bus stop this means bus needs to drive using right lane. Here's the issue the bus don't have time to switch lanes to left lane to drive straight so it turns right so it can get in lane . You turn ignore lane arrows on for buses and it no longer has this issue as it don't obey you turn right only lane anymore. Solutions add a node after bus stop for lane switching. Move bus stop before a node in road to allow lane switching. Remove dedicated right turn lane

@Painful Agenda It's turn left not right (from screenshot https://postimg.cc/jntXV9Zf ).
From the screenshot, there is no bus lane and bus stop is on the right (right hand drive).
Bus from the right at bus stop should go straight and pass 2 junctions before turn left to next bus stop.
This is simple driving, at bus stop on the right > exit bus stop and stay on the right > pass two junctions > change lane to the left (4 lane road - 2 per side) > turn left > stop at next bus stop.

Enable ignore lane arrows seem to be fixed this but I don't have any bus lane and the right lane is only go straight, there is no turn.

Just check you not told that left lane it can turn left only

I use left hand drive singer confused converting lol

Another thing the bus comes down the road turns right then turns right again. Have you made it that the cars coming from that road can only turn right into first lane and next road on right lane turn right only

I ask as close inspection your bus route go into the right hand lane when it turns then turns right to go done next road to access left hand lane

Other way around lol that's that left hand drive bug but you get what I mean. Have you made the right lane not able to turn left at that junction

No & no.
All road in screenshot are 2 way roads and no lane connector, lane limitations, lane arrow. Just use default 2 way roads (4 lane for larger road and 2 lane for smaller) without anything special.

I use normal 2 lane road and 4 lane road, all of them are in-game roads.

All junctions in this area don't use any TM:PE option. No re-route, no speed limit, no vehicle limit .
It is just all in-game roads, no special functional from TM:PE, the nodes also not broken but the bus cannot go straight.

Yes I get that I was saying make sure that when you don't have ignore lane arrows on that the bus lane can turn left and is not straight ahead only

It sounds like the bus lane itself is go ahead only by default and that ignoring lane arrows let's it ignore the go ahead only if you get lane arrows tool and check does it say straight only or is it able to turn if not click can turn left

I think I may not understand or you get it wrong.

https://postimg.cc/kD7rnXHF
The screenshot of roads without any info.

https://postimg.cc/XGcTwTrC
The screenshot of transport lines.

https://postimg.cc/GH7ngwqP
The screenshot of normal roads + transport lines using photo editor.

Bus may ignore lane arrows turned off.
Bus enter the bus stop on the right
> exit the bus stop
> turn left using detour (farther than go straight) while road is connected and there are no broken nodes on the map
> bus go back to the same road where the previous bus stop is
> bus turn left to next bus stop

Bus may ignore lane arrows turned off.
Bus enter the bus stop on the right
> exit the bus stop
> go straight and pass first junction
> go straight again and pass second junction
> turn left to next bus stop

I'm quite sure that this is a bug about routing because from first bus stop on the right, the lane arrow is go straight only (right lane) but the bus just turn left (bus ignore lane arrows turned off).

If bus ignore the lane arrows has turned on, the bus can go straight as the lane arrow. (it should be opposite result).

All of this: do not use any TM:PE feature such as vehicle restriction, lane connector, change lane arrow, nothing.

I get that but bus lane being on outside without using mod features might not allow turning left due to being far right lane. Share save and I can see for myself the issue I'm just trying help without having any access to the game

Thank you for your help.
Here is the save game that I created new one. https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=2072151295

There are a lot of assets and mods I use here, but in this map there are only few workshop use. I hope that it will not be crash on your side.
Many custom roads should be just disappear with no problem. The bus route that have this problem is named "Bus route bug".

It's fine I needed download only 360 things as I had most the 900+ it uses

I use improved content manager so I just add them with one click