One advantage cars with large sensor suites have over humans is that they can see and process information from all around them. In your specific example, the car can watch both on an off ramps at the same time, isn't phased by the "newness" of the road since other cars have navigated this section of road hundreds of times before it has, and can keep tabs on cars obscured by line of sight due to the car's ability to bounce signals off of vehicles.