STOP MEASURING DISTANCES. You can't judge them, you can't remember them, and you have to know your speed to use them anywhere near accurately.
Just have two seconds between you and the car in front. Always. You're already looking forward. Wait for them to pass something, count to two. And, yes, drivers DO do that: anyone with a brain that realises if they can't come to a complete stop before the car in front does then they are going to die.
That's two seconds between you and the stationary obstacle or the next car in the queue too. If you don't have two seconds and HE doesn't have two seconds, you're too close. Because he'll whack the object (as in the demo) and you still can't stop because he never stopped normally as if braking.
The guy in the comment above counted three between seeing the car and anything being done. So not only did you blow through your entire braking distance, but 50% over again, without even reacting, let alone pressing the brake.
Where the 2 seconds as a base minimum distance for a complete idiot that's "minus lookahead" is enough to see and stop in if you're driving anywhere near sensibly, and "revealing" something less than 2 seconds away means you weren't paying attention.
2 seconds at 70 mph is 62.5m. That's the MINIMUM distance you should have between you and a car in front travelling at the same speed. Though it can take 3-4 seconds in a modern car to come to a complete stop even in ideal conditions (but more like 2.5-3 on a well-maintained one) at worst, hitting a surprise stationary object you'll reduce the impact speed to a fender-bender not certain-death. At best, you'll have time to move around the obstacle entirely. However that's the MINIMUM. The utmost lowest limit. The least you can do and still be vaguely safe by the laws of physic and a well-maintained car and absolute attention on the road.
And magically the "2 second rule" pretty much works no matter what speed you're doing, as it scales with speed!
Seriously have we all just forgotten how to drive?