Doesn't seem like it's an unsolvable problem. The technology is still fairly new. While no computer can accurately predict the behavior of other drivers, the truth is, most drivers can't do that either. Most drivers aren't even paying attention. They are zoned out staring at some sparkly sign or the traffic lights or whatever. Even before the era of cell phones, people still drove like morons and didn't pay attention to the road.
Driverless cars don't need to be better than the perfect human driver. They just need to be better than the average idiot.