[Retric]

1. Don't confuse optimal human reaction times with real world conditions. Drivers don't have unwavering focus on the path ahead. Accidents are the exception when things go wrong, so the median accident reaction time would be far higher than under optimal conditions and really hard to measure. If a self driving car can't safely stop then it really should complain and just slow down. I can see "Speed reduced Tires balding" really would get most people into the shop and my car already tracks tire pressure and breaking. Add GPS for absolute location and it will notice if there is a problem. Listing for weather reports is also a no brainier.

2. Google is being conservative with several cars being tested at much higher speeds, don't forget in the computer world being 1/3 as fast is really far less of a jump than you might think. In terms of accuracy GPS can auto correct distance traveled over time to get much higher accuracy. Much like how most computers clocks are far closer to the correct time than their cheep HW clock would suggest.

3. Your thinking like a human. Kids are really really slow at 10mph (which is fast for a kid) 7.5 feet is over 1/2 a second. So, your car can drive like there is always someone about to jump out from every intersection and sprint across the road without being all that slow. Depending on sensor location they can also see under other cars. ED: the Front drivers side headlight is a much better location to see around parked cars than where a driver sits.

Worst case self driving cars might drive slow when stuff is right next to the road. But, if I can be productive and safe it's a non issue as most driving is not in those conditions and I should slow down anyway.