Speed, stopping distance and space
Total stopping distance has three parts: perception distance (the time to see a hazard and recognize it), reaction distance (an alert driver needs about three-quarters of a second to react), and braking distance. A loaded truck at highway speed needs more than a football field to stop.
Speed matters more than most people think. Double your speed and your braking distance grows about four times. Weight matters too, but not how you'd expect: an empty truck can take longer to stop, because brakes, tires and springs are built for heavy loads and an empty truck has less traction.
Keep at least one second of following distance for every 10 feet of vehicle length at speeds under 40 mph. Above 40 mph, add one more second. A 40-foot truck needs 4 seconds below 40 mph and 5 seconds above it. Count the seconds after the vehicle ahead passes a fixed point.
If someone tailgates you, don't speed up or brake-check them. Open up more space in front of you so you can slow down gradually, and let them pass.
