5 ms·

Assuming that a "car length" is always equal to the length of a car is the unsafe bit. A car length is simply the minimum safe follow distance based on weather,

by branon 4y ago

Assuming that a "car length" is always equal to the length of a car is the unsafe bit. A car length is simply the minimum safe follow distance based on weather, traffic, and speed. To my mind it has almost nothing to do with the literal length of a car.

giantg2 4y ago
Please provide a source for that definition. I've never seen that used anywhere.
- branon 4y ago
  I don't have a source, it's just what makes sense to me - which at the end of the day, is how we all drive. As far as definitions for "car length" go, I feel that "average length of an actual car" is just as open to interpretation as "minimum safe length at which to follow a car" - really, these are both non-definitions. Today I've learned NEVER to reference "car length" online because it's a shitty and imprecise unit of measurement. In the future I will simply say "appropriate follow distance" even though that's highly variable too.
  - giantg2 4y ago
    You could use actual distances with speed, or seconds behind. Either one can be an appropriate measurement and are used in things like Driver Ed courses. Car length may be variable, but is colloquially understood to be 15' give or take, but not more than 20'.
  - pwinnski 4y ago
    Subaru is wrong for thinking you closing on a barely-moving car at speed is dangerous, and the entire internet is wrong for thinking "car length" refers to the length of a car. Two doesn't quite make a pattern, but it suggests one. You being obviously-wrong on the second point doesn't mean you're definitely wrong on the first, but I'd be more inclined to trust the automotive company with access to crash statistics than your "never wrecked a car yet" instincts, personally. Then again, I've known two people who both proudly proclaimed that they'd never even gotten a ticket before whose driving was so terrifyingly unsafe I wouldn't get into a car with them a second time, so maybe that's my bias.
  - foobazgt 4y ago
    Safe follow distance is usually measured in time, not distance. It's a function of human reaction time plus your vehicle's ability to brake, which is mostly a function of its velocity (also greatly affected by tires and weight but there's far less variance there in passenger cars compared to personal variance in velocity). Most DOTs claim around 1.5s for reaction time, and then up to another 1.5s for braking at typical highway cruising speeds. So, 2-3s follow distance in total. Adjust down for low velocity and up for poor driving conditions.

by branon 4y ago

giantg2 4y ago

Please provide a source for that definition. I've never seen that used anywhere.

branon 4y ago
I don't have a source, it's just what makes sense to me - which at the end of the day, is how we all drive. As far as definitions for "car length" go, I feel that "average length of an actual car" is just as open to interpretation as "minimum safe length at which to follow a car" - really, these are both non-definitions. Today I've learned NEVER to reference "car length" online because it's a shitty and imprecise unit of measurement. In the future I will simply say "appropriate follow distance" even though that's highly variable too.
- giantg2 4y ago
  You could use actual distances with speed, or seconds behind. Either one can be an appropriate measurement and are used in things like Driver Ed courses. Car length may be variable, but is colloquially understood to be 15' give or take, but not more than 20'.
- pwinnski 4y ago
  Subaru is wrong for thinking you closing on a barely-moving car at speed is dangerous, and the entire internet is wrong for thinking "car length" refers to the length of a car. Two doesn't quite make a pattern, but it suggests one. You being obviously-wrong on the second point doesn't mean you're definitely wrong on the first, but I'd be more inclined to trust the automotive company with access to crash statistics than your "never wrecked a car yet" instincts, personally. Then again, I've known two people who both proudly proclaimed that they'd never even gotten a ticket before whose driving was so terrifyingly unsafe I wouldn't get into a car with them a second time, so maybe that's my bias.
- foobazgt 4y ago
  Safe follow distance is usually measured in time, not distance. It's a function of human reaction time plus your vehicle's ability to brake, which is mostly a function of its velocity (also greatly affected by tires and weight but there's far less variance there in passenger cars compared to personal variance in velocity). Most DOTs claim around 1.5s for reaction time, and then up to another 1.5s for braking at typical highway cruising speeds. So, 2-3s follow distance in total. Adjust down for low velocity and up for poor driving conditions.