News for hackers. Stuff that matters.

A comment on 7.1M miles, 3 minor injuries: Waymo's safety data looks good. Parent comment

Re:7.1M miles, 3 minor injuries: Waymo's safety data looks good by throwaway2037 on Thursday December 21, 2023 @09:43PM (#38730323) 

    25+ car lengths between vehicles that the NHTSA recommends
Is this hyperbole? I tried to Google for it, but I could not. The best I could find was the three second rule. Some back-of-the-envelope calcs: Length of Honda Accord (according to Google): 192 inches. 75 miles per hour / 60 minutes per hour / 60 seconds per minute * 5280 feet per mile * 12 inches per foot * 3 seconds / 192 inches = 20.625 car lengths. Even three seconds isn't enough to reach your recommendation of 25+ car lengths.

Note: 75 mph is 120 kmh

[ Parent | on HN ]
Re:7.1M miles, 3 minor injuries: Waymo's safety data looks good by bombcar on Friday December 22, 2023 @07:56AM (#38733655)
The actual calculation involves how fast the vehicle you’re following can decelerate, and your reaction time.

You can (usually) follow a large semi a bit closer because its braking distance is longer than yours.

But because of reduced visibility you can end up with “revealed brake checkmate” where the semi swerves into the next lane because a vehicle is stopped in the lane, which you then need to swerve or hit.

[ Parent | on HN ]
Re:7.1M miles, 3 minor injuries: Waymo's safety data looks good by bumby on Friday December 22, 2023 @09:43AM (#38734558)
They recommend estimating 4.5 seconds of stopping distance. But that’s very conservative and probably not realistic.
[ Parent | on HN ]
Re:7.1M miles, 3 minor injuries: Waymo's safety data looks good by throw10920 on Saturday December 23, 2023 @12:30AM (#38741881)
That's ridiculous. There's nothing "unrealistic" about 4.5 seconds of stopping distance - how could there be, are you thinking that the highways physically wouldn't fit all the cars spaced at that length?
[ Parent | on HN ]
Re:7.1M miles, 3 minor injuries: Waymo's safety data looks good by bumby on Wednesday December 27, 2023 @11:48AM (#38783792)
It's unrealistic if you expect the existing infrastructure to meet both that requirement, the capacity requirements, and the time requirements of people travelling. In the real-world, there are tradeoffs. People who don't understand that tend to have superficial understandings of the problem because their mental models show little nuance.
[ Parent | on HN ]