November of 2012 Senator Harry Reid’s motorcade was involved in a multi-vehicle accident in Las Vegas. The Senator was taken to the hospital with minor injuries. Two of the motorcade drivers were cited by the Nevada Highway Patrol for following too closely and making an improper lane change. Let’s look at following distances.

http://www.lvrj.com/news/two-drivers-in-sen-harry-reid-s-caravan-cited-in-crash-176899851.html

 A Typical Following-Distance Scenario

From 30 feet behind, the driver of the backup vehicle is driving at 30 mph (45 fps), the lead vehicle is moving at the same speed. Both cars approach a potential problem. The driver of the lead vehicle sees the problem applies his brakes.

The driver of the follow vehicle for whatever is not looking at the road; it takes one full second before he notices the lead vehicle is stopping and starts to react. My guess is that most who have driven in a motorcade have experienced this problem.

Step by step.

1. Once the lead car applies the brakes, it takes approximately 55 feet to stop the car at 30 mph.
2. That means the lead car is stopped 85 feet in front of a follow car (55 feet of stopping distance plus the 30 feet of distance between the cars). If the follow car’s driver is also moving at 30 mph, he is moving at 45 fps.
3. If the lead car is 15 ft. long, some quick arithmetic tells us that the rear end of the stopped vehicle is 70 feet away from follow cars front end.
4. Assuming a normal reaction time of .75 seconds, 33.75 feet is used up in reaction time (.75 seconds x 45 fps).
5. By adding the time and distance used during John’s one-second attention lapse ( 45 feet), of the follow vehicles driver we see he will not get his foot to the brake pedal before traveling 45 feet + 33.75 feet — or approximately 79 feet (45 Feet + .75 x 45 Feet).
6. Since it takes follow driver 79 ft. before he gets his foot on the brake, he will hit the lead car without ever touching the brake pedal — again, a life-changing experience and not something you want on your resume.

Scenario Two

If we use the same scenario, and add back that one second of diverted attention, an accident still occurs, even with the follow driver applying the brakes the instant he saw the tail lights of the lead car come on.

1. It still takes the driver of the lead car .75 seconds to reach the brake pedal, which is approximately 34 feet. It takes 55 feet to stop the car. Therefore, it takes 89 (34 plus 55) feet to stop the vehicle.
2. The rear end of the lead vehicle is still 70 feet from the follow car. The difference between Scenario One and Scenario Two is that, in this scenario, follow car driver will collide with the lead car while his foot is on the brake – still not good for the resume.  The problem? He was following too closely.

ABS or non-ABS braking, throwing out an anchor, dragging your feet, all the fancy braking techniques in the world won’t help if you follow too closely. So, when it comes to following another vehicle, it’s simple: Keep a safe distance between you and the car ahead.

How Much Space Should You Keep in Front of You?

One good rule is to keep at least one second for each 10 feet of vehicle length at speeds below 40 mph. For the average 20-foot car, this means if you’re driving below 40 mph, you leave two seconds of space between you and the car ahead.

Calculating How Much Space You Have

1. Pick a fixed object on the road (a shadow on the road, a pavement marking, or some other clear landmark).
2. When the car ahead of you passes the marking, count the seconds (one thousand and one, one thousand and two, and so on) until you reach the same spot.
3. Compare your count with the rule of one second for every 10 feet of length.
4. If you pass the landmark before the time is up, you’re driving too closely.

After a little practice, you’ll soon instinctively know how far behind you should drive.  Also remember that when the road is slippery, you need more space to stop.