They almost always underestimate the amount of curvature. Peoples' motion perception is highly inaccurate under some conditions. Drivers tend to overestimate the speed of slow moving vehicles and underestimate the speed of fast ones. Perception of motion in cars immediately in front and behind is especially poor. It is difficult to tell,for example, that the car in front of you is stopped rather than moving.
Drivers are also very poor at remembering traffic signs.
Automobile-bicycle accidents occur most often at intersections where the driver is turning right and the bicycle approaches from the right. As a result, they don't see the bicycle approaching from the right.