Probably in the sense that at a slower speed, op would have been able to avoid the bad driving from the other driver. Assuming that OP was driving at 60kph originally, a 15kph slower speed equates to a roughly 0.75 extra seconds of reaction time (assuming braking acceleration is roughly 7.5m/s2). Given that an average humans reaction time is somewhere between 0.25-0.5 seconds, that means 15kph speed difference would have allowed OP to react and affect the situation. Even at higher initial speeds, 15kph gives your more than half a second extra time.
The momentum point is very valid. But the slower speeds provide more time for drivers and others to react. That in turn gives you much more time to break and scrub off that extra momentum.
At 50kph your reaction distance is about 15 meters, at 25kph it’s half that at 7.5meters. (Assuming reaction time of 1 second, which seems to be a realist value).
7.5 meters is quite a bit of distance, and in a busy city will make a lot of difference.
Good driving doesn't have that much to do with your reaction time. 40% slower to respond, with a well planned drive, is a lot safer than 40% faster driving too close.
Well no; speed does increase severity in the case of a collision as you say, but it also directly impacts your stopping distance, even at the same level of alertness/reaction time/etc. If a kid runs out in front of your car, you are both more likely to hit them at 30 mph than 15 mph (due to not being able to stop in time) and more likely to kill them having hit them.
Even if you still crash, the extra second of braking time can take off ~10-15 mph [0], which at 60 mph V(t=0) is ~40% of the energy that would otherwise dissipate into your car and the cars you hit.
It is not just a matter of reaction times. It is mostly of stopping without harming you, which at 70mph is rather difficult if the vehicle in front brakes too hard.
I've been involved in at least two accidents that were out of my control, one involving a car, and it was obvious in both cases that going slower saved my ass. I can see that below a certain speed you get more wobbly, but she seems to have been going in excess of 30 mph, at which point your own reaction time becomes the biggest issue.
The relative speed difference of 130km/h means you're closing in on the traffic in front of you at 36m/s. That doesn't sound like much but if you consider how long it takes from checking the mirror to changing lanes, that's often just not enough time. Numerous times I've had the situation where I checked the mirror and by the time I've changed lanes, some car almost rear ended me. Relative speed differences like that are just a recipe for disaster and the only way to fix that is to make the fast car go slower.
> which part of the fatalities happened > 130kmph?
Usually (not always) you realize that something bad is going to happen so you are going to brake. Let's assume there is an obstacle in front of you that is 150m away. After a reaction time of 1 second, and with continuous braking over 100m you are able to get from 180kmh to 100kmh at time of impact, but if you had started from the generally suggested 130kmh, you would have stopped 40m before the target (assuming -8.83m/s^2 braking acceleration).
Not wanting to rub salt to your wound but there is a difference between able to tell if a car went fast or slow, or definitely slower than the speed limit, or exactly 58.4km/h.
Speed determines time to stop including stopping distance and reaction time. For every second of reaction time per 10kmph you add about 4 meters of distance travelled before you even hit the brakes. So best case if you aren't looking at your HVAC, at 50kmph you will start the stopping process in about 28 meters, and at 60kmph it will be 33.3m and take longer to stop once you hit the pegs.
Doesn't sound like heaps but that is actually your margin for error, just 4m. If something jumps out in front of you at 28 meters away, at 50 you will have had 4 meters to stop, which modern cars can do, and at 60 you will hit them at the full 60kmph. The Australian government has some great road safety clips on the subject, I might try and find them.
It's absolutely not nonsense, I suggest taking some basic high-school physics.
Reaction time is the time for the vehicle to come to a stop, not for the driver to first notice an issue.
At 60 mph it will take many meters and seconds to deaccelerate, assuming the driver can take exactly the correct action:
Estimate here is about 4 seconds, under perfect conditions. 5 seconds is more than reasonable, considering you also need to realize the other driver is acting erroneously.
Or weather/road conditions. Reaction time is irrelevant if you happen to be driving over an irregular/wet/oily/sandy/etc section of roadway at the moment maximum braking force is demanded.
It has a lot to do with reaction times as well. At higher speeds you've already run into the idiot swerving into your lane (or whatever) by the time your brain processes image.
There is a threshold where the speed will likely injure, not kill. It's prudent to keep below or near that speed, so you have at least time to bring your car down that speed when braking, if not managing to come to a halt.
Breaking distance and collision energy scale with square of the speed. So reduction from 70 to 60 is 27% reduction.
Also minimal safe distance is 3 seconds at your current speed. If you can't keep that distance because of traffic - you should slow way down, not to 60 km/h but much lower. So either your comparison isn't fair or the person doing 60 km/h with 2 seconds of gap is the reason the road is unsafe, not the traffic.
It's interesting that the car was exceeding the speed limit of 35 mph. I would assume the car would stay at or below the speed limit. Who gets the speeding ticket in this case? Does 5 mph affect the reaction time such that it could have noticed and taken evasive action?
I agree with your instructor. That said, modern cars can stop in /much/ shorter distances than previously, largely thanks to improvements in tire technology.
Nearly every production vehicle available today can brake from 60mph in less than 140ft, more performance oriented vehicles can do so in under 120ft. The standards for “safe stopping distance” used in the US triple this distance to account for slowed reaction time because drivers are not attentive.
Realistically less than doubling these figures is correct for attentive drivers. 60mph is 88 feet per second, and 1 second is plenty of reaction time for an attentive driver, meaning 200-240ft total stopping distance, closer to double the distance the vehicle is capable of rather than triple.
So if the visibility is less than 200-240ft, you should be going slower than 60mph. 240ft isn’t very far in a car though, it’s roughly the distance traveled in 3 seconds at 60mph. There’s certainly some country roads I’d slow down on, but if you’re paying attention you’re well good on most.
For what it’s worth, the average reaction time of a gamer is 150ms, so a full second is plenty of margin of error.
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