This occurs in places all round the track but the best example is the tunnel at Monaco. Firstly to say I have all graphics options at max. As you come round the right hander and first see into the tunnel, the tunnel wall appears lit but then as you get closer, it suddenly snaps into being dark or in shade. I thought that this must be because the max distance cutoff for calculating whether objects are in shade was too low but this only seems to occur on certain objects. Being a good little racer, I look as far down the track as possible and this issue can be offputting and make it difficult to see upcoming corners due to the changing graphics as you approach. Maybe this is a driver issue with my graphics card, maybe not. Does anybody else have this? I'm using a GTX480 with latest drivers.
Haven't noticed it with the tunnel but have noticed the same sort of behavior at other places. HD6870.
After playing a bit more, I've seen that it happens at different places at different times of day. In some light conditions the tunnel is OK, sometimes it isn't.