Well, yea, actually it would. Because the vehicle would detect the movement long before I do. And even in that situation, hit the brakes is the right answer.
> every other car could slam on their brakes at any time
Or veer out of the way of an obstacle you can't see, leaving you to either similarly veer or collide with it. IOW, do not assume you only need to account for your own reaction time; rather assume the vehicle in front of you can instantly stop moving and you must account for both your reaction time and your vehicle's stopping distance.
That might be less than ideal if you were going downhill. Or if you had accelerated to maximum speed, were heading toward an intersection, and planned to hit the brakes before you got there.
That calculation would probably be wrong anyway, unless you have a lot of practical experience with emergency braking. I constantly underestimate my reaction times.
I didn't say you can't drive a car without being cautious.
I said you can't drive it without constantly braking the moment you detect an object, irrespective of what the object is doing. (e.g. moving into or away from the driving path).
i.e., just because an object was detected 6 seconds before impact did not mean the car ought to have started braking at that moment. It could be that the object was 200 feet away and moving away from the car's driving path, 6 seconds before impact. It'd be absolutely ridiculous to brake in that situation.
We have no information about this context, e.g. the car's data or determinations within the 6 second window. We only know it detected an object 6 seconds before impact.
It appears like the person I was replying to implied 'the braking distance was 180 feet, but the person was 380 feet away, thus uber could have prevented killing this woman had it not shut off the brakes'. In reality, the 6 second figure isn't relevant. What is relevant is the context that allowed a reasonable driver/AI to determine at a particular point in time, that the car should have slowed/braked. And we don't have that information yet. That's what I'm interested in.
I always wondered if you need less than two seconds if you're behind a vehicle that can't stop very fast (e.g., a large truck). Your superior stopping rate could make up for the decreased reaction time.
But the sensors and actuators that are keeping him in his lane would surely fire the brakes far faster and harder than he would while reading his magazine.
In fact, since human reaction time is on the order of 200ms, the car could likely see what's going on, double-check, and then hit the brakes before he noticed what was going on, even if he were paying rapt attention and expecting you to slam on the brakes.
What is the reaction time of these systems? There are papers on the Internet but they are behind paywalls (that I could probably get through if I were an automotive engineer).
They can't detect me slowing down before I start slowing down. So if it's t-4 until impact and I'm still moving at full speed, they would need to start braking now if they can't stop in 4s (assuming the worst case that I continue on my current trajectory).
That being said, I'm happy to find my assumptions about stopping time are incorrect and a car traveling at 25mph can stop in less than a second. So on busy NYC streets this wouldn't be an issue. Even at 50mph it appears that stopping time is sub 3s, so the vehicle could probably have avoided this collision if it were running a more intelligent program.
Perhaps you would be so kind as to contend with what I actually said. I did not actually say a human would have stopped in time. I said a human would have braked and swerved.
The car can begin to brake right away, and must certainly be expected to have a faster reaction time than a human. Whether it started to brake seems like the most important question here.
It wouldn't work for everything, but you can cut that time by preemptively reacting to conditions. Say you're going around a blind corner, you can start slowing just because your visibility is lower and you don't know what's over there. Or you can see cars who intend to move over several lanes at once and kamikaze into the lane ahead of you and slow down because you know that all the people in front of you are likely to brake due to this.
There are quite a few scenarios where I spot trouble before it happens and have an effectively negative reaction time with respect to whatever is causing people ahead of me to brake.
How would they be able to quickly take the wheel and brake if something happens? I think the opposite is true, if you need longer reaction time it's probably a bad idea to not be fully immersed in the driving until an accident is imminent.
> When the vehicle ahead emergency brakes or stops you have the growth of size of the target to gauge by. That's not much movement, until the last moment when it's far too late to evade.
You see the brake lights up, and as long as you're alert and keep some distance you're going to be alright. If you're not alert and/or driving too close you hit it.
Yeah, but you have to be following the car in front of you at a distance that takes into account your reaction time and the actual braking distance. This time, the guy slammed on his brakes because of a yellow light which is maybe not a good reason... but it could have easily been someone running the red light, some kid running out into the street after a ball, the car's wheel flying off, etc.
reply