Rules of thumb for determining a safe distance to be behind a vehicle:
(1) 1 car length for every 10 miles per hour of car speed
(2) 2 (or preferably) 3 seconds behind
where:
• 1 mile is 5,280 feet.
• 1 mile per hour is 1.46 feet/second.
• 15 feet can be used as a car length.
Assumptions when determining a safe distance:
(1) That the driver can respond in 1 second.
(2) That the cars are traveling at the same speed.
(3) That the cars are functioning the same.
Reasons to increase the safe distance:
(1) poor visibility (night, sundown, fog, snow, etc)
(2) slippery road surface (rain, ice, oil, or anything else reducing traction)
(3) slow response times (fatigue, illness, medication, intoxication, distraction)
(4) need to stop unexpectedly
(5) problems with brakes
(6) towing something heavy that increases the vehicle's momentum
