Have you ever had someone in front of you swerve out of the way, leaving you facing a stopped car? It's exciting, let me tell you. The idea of safe following distance is predicated on the car in front of you not being able to defy physics when they stop, presumably their braking power is similar to yours.
Sure. But, in this case, there were three+ cars. The Tesla that stopped, the car immediately behind the Tesla swerved, and the third car ran into the Tesla.
The driver of the third car claims there was nothing he could do. That's baloney, as the car that was EVEN CLOSER to the stopped Tesla was able to react. Fact is, he was following too close and/or not paying attention, and crashed.
I agree that the third car is almost certainly at fault. "Didn't have time to stop" is nonsense in every case except if some idiot cuts into your lane within your safe stopping distance and then immediately brakes.
Drivers need to think of every vehicle as being in a moving block[1] signalling system with each block being ~290m long (actual vehicle in the middle of this block) in wet conditions at 110kmh-1[2] and ~230m long in dry conditions at 110kmh-1[2]. No vehicle should ever enter another vehicles moving block. Obviously the type of vehicle, tires, road surface material, etc can reduce (or extend) those required block lengths, but you generally have to assume worst case scenario because how are you to know whether another vehicle has bald tires or is operated by a person who is fatigued or distracted and taking much longer to respond than they should.
If the driver of car 3 could not see past car 2, and car 2 hadn't realised the Tesla had stopped, and instead swerved out the say 1 second / 90 feet (assume 60mph) before collision, that would give car 2 traveling at a reasonable gap no more than 3 seconds / 270 feet to recognise what was going on and stop.
Should have recognised something odd (a broken down car) within 1.5 seconds, leaving 1.5 seconds to slow down.
Applying brakes from 60mph would mean you'd still be traveling over 40mph when you hit the back of the car.
Thus you need to give more than 2 seconds if you can't see beyond the car in front
Yes. But because I was following at a safe distance from the car in front, that gave me adequate time to slow down and stop without hitting the stopped car.
Safe following distance isn't predicated on defying physics, it means assume the car in front might stop dead for any reason - hitting an unseen obstacle, swerving to reveal an obstacle, sudden mechanical failure, animal collision, whatever. The distance you need to react and stop is around 100 metres at 70mph. Therefore, that's the distance you should keep from the car in front.
As a bonus, it gives any tailgaters more time to notice you're slowing down too. Hopefully this means you're less likely to get pancaked between two cars.
>Safe following distance isn't predicated on defying physics, it means assume the car in front might stop dead for any reason
No, it's based on assuming the car in front might brake at standard non-physics-defying rates at any time. The 'safe' following distances that are advised don't allow for encountering stationary objects. That's why they're called following distances, as in, you're following another vehicle that obeys the laws of physics.
Imagine you're following - at a safe distance - a vehicle. The driver of the vehicle you're following doesn't notice that the car ahead of them is emergency braking. They notice at the last second and swerve around it to avoid a collision.
You are then face to face with a nearly-stationary object which was concealed from you by the vehicle ahead of you.
From your perspective, it fell from the sky. If you don't swerve, a collision is unavoidable.
I think we are in agreement with the the situation, I just disagree and think you're either driving too fast or following too close. Your logic leads to pile ups, as in the event of a pile up, a car stops dead unexpectedly infront of you and you have nowhere to swerve.
I can't speak for the USA, but in the UK, if someone swerves and you rear end a stationary object, you are at fault. Indeed if you rear end another vehicle, you are nearly always at fault (unless e.g. they pulled in front of you then immediately slammed the brakes).
Stopping distance at 70mph is about 100m and "The safe rule is never to get closer than the overall stopping distance". This is a minimum - in adverse conditions the distance should be even greater.
This means when you see the stationary object, you're about 100m away, which is adequate time to stop IF you're paying attention and your car is well maintained (we have annual MOTs to ensure this).
I don't know about the USA, but in the UK our stopping distances assume the car might become stationary at any point. That is, they are actually stopping distances - not following distances. If you follow closer than that on your test, you will fail.
Frankly, I can never imagine seeing an empty football field worth of space between two cars on a busy freeway. Even if you attempt to create such a space, other drivers will fill it.
This assertion about following distance feels purely theoretical for busy freeways.
Caveat: I drive in the UK so driving quality may be different here. I always maintain adequate stopping distances on busy motorways. People do fill those gaps occasionally and it does result in me driving slightly slower on average by a couple mph maybe, but it's perfectly possible to maintain a gap.
A lot of experienced drivers here claim it's impossible too, but there's a good way to know that it's not: on your driving test, you'll fail for following too closely, so most people manage to keep an adequate stopping distance for the test. Following closely is usually a habit picked up when someone becomes a more confident driver.
The real reason is probably people don't want to take the tiny average speed hit or find it unfair that they keep letting people in.
