5 ms·
There is a 500 m long street in front of my house where it is customary that people cross it everywhere and cars are just expected to stop for the people. There
by yoodenvranx 11y ago
There is a 500 m long street in front of my house where it is customary that people cross it everywhere and cars are just expected to stop for the people. There are no traffic lights or pedestrian crossing or any special rules, its just that people started doing this decades ago and now it is just tradition to do this.
So now you have a long street where tons of people are crossing every 10 meters during the day because it's a quite busy shopping district.
Although cars are driving slow, it must be very hard for autonomous cars because there are people everywhere running in every direction.
- Retric 11y agoDon't forget computers have vastly faster response times than people. A car going 5mph with 10ms reaction times can stop in ~1 foot. http://www.random-science-tools.com/physics/stopping-distance.htm http://www.random-science-tools.com/physics/stopping-distanc...
- marssaxman 11y agoDo you want to be inside the car when it does that? It is not going to be much fun unless you are paying attention and bracing yourself, in which case I'm not sure I see the advantage of letting the computer do it for you.
- Retric 11y agoYou are probably overestimating the jerk from that. 5mph has (1/12)^2 = 1/144th the energy of 60mph. Passengers often don't pay attention to what's going on and breaking force is generally not enough to really mess with people. That said, the default is not going to be stopping within 1-2 inches of pedestrians, rather it's going to gradually slow down to deal with pedestrians while trying to maintain forward progress. The point is a self driving car could be more aggressive than most people while staying safe instead of freaking out and just stopping because people are jaywalking.
- marssaxman 11y agoYou're right of course. It's hard to imagine any useful vehicle spending much of its time moving at only 5 mph, though, so I suppose I'm really imagining what such a stop would be like from a more normal travel speed like 20-25 mph.
- Retric 11y agoI am picturing this more as an extreme edge case than anything else. If a person can safely do 20-25mph in an area then a self-driving car should be able to do the same thing. It's the edge case where a car needs to cross a really high traffic area that's going to be an issue and people can't do 20mph right in front of a high traffic box store entrance etc. Further, going slow for a few hundred feet really does not take that long.
- erikpukinskis 11y agoI would VASTLY prefer to be in that car than to be in a different car with a human driver and watch a person get killed by the vehicle I'm riding in.
- marssaxman 11y agoNobody is going to die from a 5 mph collision. It's not even likely to break any bones. At 30 mph, the chance of death is still only 5%! There may still be reasons to prefer robot cars for low-speed environments but the probability of such a vehicle striking and killing a pedestrian is already very low, so that is not relevant to a discussion of a robot car's ability to stop very rapidly at very low speeds. http://www.nhtsa.gov/people/injury/research/pub/HS809012.html http://www.nhtsa.gov/people/injury/research/pub/HS809012.htm...
- Symmetry 11y agoThe "every direction" bit is actually something autonomous cars handle far better than humans since they can have eyes pointing in every direction. The hard part is noticing that someone waiting at a crosswalk wants you to stop so they can cross.