I'd make that 3 seconds. Longer at high speeds, if the roads are slippery or if you drive a heavy vehicle. You can shave that figure down a notch if you're in a long column of slow moving vehicles ("bumper-to-bumper"), but be aware of the risks involved.

1 second would make a serious violation of our local traffic laws and the ticket if caught is quite stiff. Less than 1 seconds and you're borderline to serious legal trouble (you go to court, not just a ticket) and loss of driver's license. Your local laws may differ.


Remember that you shall be at a mental state of very high alert AND have the foot ready on the brake pedal to have reaction times less than 1 second. If you don't suspect anything in particular to happen, expect 1.5 seconds or more. At least 1.5 seconds is the realistic reaction time in your every day scenario, not the "I train myself to show how quick I can react in this test"-figure.

Then why don't you crash more often if you need this long to react? It is because traffic usually follows a predictable pattern: You put your foot on the brake when you expect you'll need to slow down. I am talking about the time you need to react when something unexpected happens.


It is not just a question of YOU being able to stop. There is also a vehicle behind you. If you have a gap of 3 seconds you can stop much more smoothly. This reduces the risk of being rear ended because the guy on the phone behind you does not have your superior awareness and reaction time.

The next time you're driving, count start counting thousand-and-one, thousand-and-two, thousand-and-three when the rear end of the car in front of you passes a sign post or other reference point. Stop counting when you reach that reference point. If you can't make it to two you probably won't be able to stop if that guy unexpectedly slams on his brakes - you'd hit him for sure. Make it to three and it gives you a much better margin for the unexpected.