Usually there’s a laggy lobby or two and you can just hop into a different room and it’s all better. The lag in the bad rooms is usually not that bad either if completely honest. However today every lobby I’ve been in has atrocious connection, to the point that if I’m next to someone in a turn they’ll lag into me and I’ll go flying off the track and they’ll keep going like nothing happened. I can’t even play today, the only luck I’ve had is if I start out in first and I’m driving one of my faster cars so I can avoid everyone. There is still the issue of the game speeding up and slowing down erratically, often at the entrance of or in the middle of a corner. I haven’t been able to enjoy playing at all today because of this.
Try having your Xbox One be the only device in your home connected to the Internet & see if that helps. Wired or wireless. Worked for me!
The problem with that is I live in a household of 4, all of whom have their own computers and devices and such. However I don’t think that was the problem as it was around 2-4 in the morning I was noticing this.