It was completely blocked for me trying to get in. I was waiting at the traffic light to turn left, and when it went green and I turned down that street, it was already blocked up in the on-coming lane. I thought the middle lane was for turning, but cars behind me came up beside me wanting to turn in and I was blocking them.
I used the console to clear the traffic, but in the time it took me to pull in and fuel up, it was already clogging up trying to get out. I didn't have to clear traffic with the console though, it was moving, slow but moving and I was able to nudge out enough to make the AI stop and let me out.
None of the mods I use increase traffic density, but I think the longer train mod caused the traffic to bunch up when a train passed, and after it passed, they piled in and there wasn't enough room so it completely blocked up the entrance.