While this may be intentional, I do believe it is a bug.
In bidirectional roads, when there is a curve, city cars seem just to stop and not proceed in one of the directions (see attached picture). This causes serious traffic jams... In the picture, the cars in the northbound lane seem to proceed (its busy, so they're slow...), but in the southbound lane they are just stuck!
Once the city cars are removed, player convoys seem to work fine.
In addition, city cars seem to stack when they stop, instead of lining up one behind the other. Sometimes there are dozens of city cars on the same tile - you delete one, and nothing happens because you can't even see the car you deleted.
Thanks!
I believe that the stacking problem, which is not unique to Experimental but also appeared in Standard, has been fixed, and the fix is on the devel-new branch; the other issue is not one of which I have been previously aware, but the code for moving vehicles on ways is not code that I have altered, and so this problem is likely to be present also in Standard; can anyone confirm whether this is the case?