30 km/h is 8.3 m/s, are you implying the driver reaction time is 2.5s? Or is this chart for mentally challenged drivers?
Iโm trying to figure this out too. Those distances seem really suspicious. At 30km/h, Iโm pretty sure I can stop my (admittedly small) car in less than 1 car length. Maybe half a car length, something like 2m? Way less than 9m.
And looking at 60km/h, thatโs 17m/s and they are claiming a 43m stopping distance. That would be like hitting the breaks and your car just slides on the pavement for 2.5 seconds, traveling the distance of an Olympic swimming pool, before stopping. Thatโs only reasonable in the worst possible driving conditions. Or maybe with an enormous and heavily loaded vehicle?
Or maybe Iโm being too optimistic here? Maybe these are numbers from actual accidents and in real life people hit the break slowly at first and stuff like that?
Sure, if someone says 3-2-1 brake and youโre expecting a test. But thatโs now how people react while driving every day.
I get that my performance will change depending on whether Iโm expecting a test or not. But I think if my car has its breaks slammed, itโs going to stop in less than 9m starting at 30km/h, regardless of whether itโs expecting it or not. Itโs the stopping distance that Iโm feeling is larger than it should be.
A couple questions. Is the stopping distance in this diagram the distance the car travels after the driver has completed their reaction time and started hitting the breaks? And where does the value from this distance come from?
I wouldnโt have thought to ask you before. A lot of times people just post things they find online that impact them in some way. But you seem to have a lot of knowledge that goes beyond just seeing this image.
And, anecdotally, I was driving late last night and an animal jumped out into the road ahead of me. I would like to avoid hitting an animal just as much as hitting a person. But I didnโt immediately slam on my breaks to stop the car as quickly as possible. I gradually squeezed that break pedal until I was rapidly slowing. So maybe my assumption about stopping distance is wrong. Maybe the car can stop faster, but when driven by average people it doesnโt, simply because average drivers donโt stop optimally.
Yep. 2.5s is the average perception reaction time. This includes
- Perceiving the person
- Understanding the situation and thinking about whether you need to stop
- Moving your foot to the brake pedal
Keep in mind, most people feel comfortable driving and not expecting to have to make an emergency stop at all times. Sure, youโd be ninja-fast if you were in some test environment where you expected the hazard and were trigger happy on the brake but thatโs not the real world.
A few US states, including California, have adopted a standard driver reaction time of 2.5 seconds. The United Kingdomโs Highway Code and the Association of Chief Police Officers ACPO Code of Practice for Operational Use of Road Policing Enforcement Technology use 3.0 seconds for driver reaction time.
