What happens if there is a loss of electricity? How about a computer crash? In the event of a computer failure, can vehicles be programmed to simply drive a straight line and slow down to a stop? What happens if they are on a curvy mountain highway?
What happens if there is a loss of electricity?
You maintain a battery backup that only needs to power the computer for ten seconds or so, until the vehicle is safely stopped. This is trivial. All laptop computers come with such a battery :-)
How about a computer crash?
Often hardware that is required to be highly reliable has multiple backups. The Shuttle flew on three computers, and those computers' decisions passed through a voting module. If there was a difference in calculations, two computers overruled the third one. As the cost of computer hardware is already inconsequential, this is a non-issue. This is already done at every telecom, ISP, and bank. Crashes of their networks are extremely rare.
In the event of a computer failure, can vehicles be programmed to simply drive a straight line and slow down to a stop? What happens if they are on a curvy mountain highway?
As the computer will remain fully operational after the failure, it will do whatever is most appropriate to safely park the vehicle, including the special rules for parking on a slope. But as the final backup, if computer control disappears, two simple parts (resistors!) can gently drive the brakes to full and the accelerator to minimum, and then the engine stops with gearbox engaged.
Generally, there are many things that can fail in a vehicle; the computer should be able to decide what to do in each case - the failure of brakes, of the gearbox, of the engine, of a wheel, etc. However this does not appear to be complicated, as operational margins of all those devices are well known. For example, a vibration sensor at the left front wheel reads high, whereas other wheels are OK. This means that the left front wheel is flat, or otherwise defective. (If you have a pressure sensor, it helps.) Brakes will be checked on each application by several acceleration sensors (you can get them for a few dollars at SparkFun.) The engine response should follow the accelerator position; and so on.