1998 GMC Jimmy Owner's Manual - Page 187

Braking Braking action involves perception time and reaction time. First, you have to decide to push on the brake pedal. That's perception time. Then you have to bring up your foot and do it. That's reaction time. Average reaction time is about 314 of a second. But that's only an average. It might be lesswith one driver and as long as two or three seconds or more with another. Age, physical condition, alertness, coordination and eyesight all play a part. So do alcohol, drugs and frustration. But even in 3/4 of a second, a vehicle m htravels 66 feet (20 m). moving at 60 mph (100 k / ) That could be a lotof distance in an emergency, so keeping enough space between your vehicle and others is important. Sometimes, as when you're driving on snow or ice,it's easy to ask more of those controlsystems than the tires and road can provide. That means you can lose control of your vehicle. And, of course, actual stopping distances vary greatly with the surfaceof the road (whether it's pavement or gravel); the condition of the road (wet, dry, icy); tire tread; thecondition of your brakes; theweight of the vehicle and the amount of brake force applied. 4-6