What I mean is the light doesn't actually cast on either the road or on the car itself...so when you're in the cockpit you don't get a cool light/shadow cast from each light, it's basically like the light isn't doing anything at all.
Forza 5: https://www.youtube.com/watch?v=lM7D7tjWfqs
Forza 6: https://www.youtube.com/watch?v=jYWKaQcDmD0
Here's some quick daytime footage showing it, and it's been standard since I'm positive at least Forza Horizon 2. I don't want to sound too accusational with this, but do you play the games? Those tunnels are really prominent, I'm surprised someone would have the impression the series didn't do that sort of lighting (I play in-car usually, so it may stick out more for me).
Edit: Ah, you caught it too.
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What's this about shadows from cars not casting on the environment? These are from the video in the OP:
Am I misuderstanding that?