Bug? Traffic suddenly stops midway although road ahead is free

[Planck]

Take a look at the screenshots below. The line of cars stops in the middle of the road although the path ahead is free. This is causing a giant traffic jam and inhibiting the flow of services to the neighbourhood. Such behaviour started suddenly and sadly I cannot pinpoint the reason. It seems to me this is not intended, but I'd like to confirm whether this is a bug or something else entirely.

After a while, a few cars go through, but the majority stay back stopping at the same point. It is as if they were stopping at an invisible traffic light. Strangely enough, I've checked the metro lines underground and found a "traffic jam" with the metro trains displaying a similar behaviour. Maybe the cars are considering the metro line as an intersection, since it crosses right below the street?

If anyone needs it, I can provide a savegame file.

 

[Planck]

A little update to the problem:

The metro line was in fact acting as a sort of blocker to the flow of traffic. Deleting/rerouting the line made the cars suddenly start going again. That's the good thing. Now the bad thing.

After some time, the problem reappeared somewhere else. This time it was at a traffic light. The cars suddenly stopped going forward, even though they had green light. Same behaviour as before: one car goes forward at a time, all others stay back, creating a massive traffic jam and inhibiting services from getting to the population, killing my citizens and creating all sorts of nasty problems.
The difference here is that there is no metro line acting as a sort of intersection, so I have no idea what could be the source of this bug.
Notice again that this is not normal traffic due to the intersection. It's rather a problem that all cars could go forward, but they simply don't.

Edit: Found the problem. The ambulances are trying to turn and get to the small street to the left. However the small block is a loop of a one-way street, and the only connection to the avenue is an exit. So the utility cars want to turn, but can't use that "exit street", and stay there stuck, blocking the other cars. This was of course stupidity on my part, but I think there should be way of either warning the player that there's something wrong, or preventing houses from being built there in the first place if the vehicles can't reach them. The first problem above with the metro line as an intersection still stands, though.