Maintaining minimum distance between cars, bit confused.

Cellar_Door

I must be an idiot, I can't get my head around this.

I'm told the minimum safe distance to leave between vehicles travelling at 100km/hour on a dry road is 62 meters, and this is based on the "two-second rule".

At 100km/hour (aka 100,000 meters/hour), you're travelling 1666m every minute (dividing 100,000m by 60), and 27m every second (1666 divided by 60).
In two seconds you travel approx 55m. (27 x 2)

Where does the 62 figure come in? And then I'm told the normal stopping distance of a car travelling 100km/h on a dry road is 77 meters.

Do they simply add a bit extra to the two second rule, or am I missing something else entirely?

Witcher

http://theory-tester.com/questions/372

The figure of 62 metres is based on the two-second rule. If you follow the two-second rule, you will leave approximately 1 metre between you and the vehicle in front for every 1.6 km/h of your speed.

Greenmachine

It is also related to reaction time and braking time. It assume ideal driving conditions. I believe different time and distance are provide for wet conditions to illustrate this point.

ardmacha

Cellar_Door wrote: »

Where does the 62 figure come in? And then I'm told the normal stopping distance of a car travelling 100km/h on a dry road is 77 meters.

Do they simply add a bit extra to the two second rule, or am I missing something else entirely?

The two second rule is based on the vehicle in front braking sharply, not stopping dead. It gives you time to notice something has happened and brake, and your brakes and tyres may not be as good as the vehicle in front. Of course if the car in front stops dead, e.g. frontal collision, the distance may not be enough, but in this case hopefully you would start to brake sooner.