To make things short, there is a small section of the highway near Astmoor where the random civilian NPC drivers perform a U-turn from the far lane of the highway, cut over the green strip of land between the highways, to the far lane of the other highway, then drive back into the direction they came from.
I’m very confident they shouldn’t be doing that because the NPCs just keep crashing into each other as the AI in the other lanes doesn’t acknowledge those U-turns, and so they just pile up there.
I made two videos of this happening:
- Forza Horizon 4 - 2018-Oct-24 - Bug Report for Highway pathing issues: Part 1 - YouTube - made during British Racing Green, chapter 8
- Forza Horizon 4 - 2018-Oct-24 - Bug Report for Highway pathing issues: Part 2 - YouTube - made during free roam
And here is a screenshot of the map where it happens:
This can be reproduced indefinitely, and persists through restarting the game.
I’m on Windows 10 Pro 64-bit, the game I bought is the Ultimate Edition directly from the Windows Store, and the game is updated to the newest patch (Ver. 1.203.504.2.HV).