Re: Have I missed something?
Why would autonomous cars (when they arrive in 2080) need to read road signs?
Well, two obvious reasons.
Firstly because they convey mandatory information to which the vehicle must adhere immediately, not once someone gets around to updating the map. Getting a dozen speeding tickets because what was a 30mph limit on Friday is now a 20mph limit on Monday and your map hasn't been updated yet, is going to be annoying, and expensive.
Secondly because non-automated road users (other cars, trucks, vans, pedestrians, cyclists etc) will be using the signs to inform their decisions - understanding what those road users are likely / supposed to do next will be a key part in not running them over.
The problem seems readily solvable - use a better image set for road signs, and make sure the car understands that not everything at the side of a road is a mandatory road sign - some are just adverts for the village fete, or hangover food.
Some signs cover a wide, changeable, and semi-unpredictable area. "Wild ponies or horses" being a good example, or riding schools. Many horses apparently confuse plastic bags stuck in hedges to be a vortex to another universe, and are likely to misbehave. It'd be best for all if the AI doesn't assume the horses will be in the fields, or moving slowly at the side of the road.
Temporary road closures for say road races (running etc) won't always be known about in advance in CA. or wherever the update is done, and if you're relying on humans to ensure the maps are correct at the time of use, then you're going to get human error. Anyone having lived in Newcastle-under-Lyme will be very familiar with truckers getting lost looking for Newcastle-upon-Tyne, at least in the days before GPS. People make mistakes, so cars relying on maps updated or created by humans are going to need to drive to the conditions in play on the road at the time of arrival, not what they should be according to the map.