How to Determine Car Braking Distances

Careful computations of car braking distances are required to determine the exact measurement for adequate braking. Braking distance in its mathematical format doesn't take into account weather and road conditions. In addition, this calculation doesn't consider the mechanical condition of the car. Other factors, such as driver awareness, health and level of impairment (if at all), help determine braking distance. Calculating car braking distance includes computing both thinking distance and actual braking distance. Knowing your car's braking distance is a good tool to use in conjunction with safe-driving practices.

Instructions

1. Determine your individual thinking distance. This distance is the amount of time required for you to see an obstruction in front of your car and react to it by pressing the brake. Thinking time includes the first step of realization and then reaction time. In the case of braking, thinking distance includes the time it takes the driver to move her foot from the gas to the brake. In general, this value is roughly proportional to your vehicle speed in miles per hour. For example, if you are driving at 30 mph, thinking distance is 30 feet.

2. Consider the typical-sized vehicle's average braking distance. Stopping distance can be figured by using a general formula, in which X = speed.: X(squared)/20 = braking distance in feet.

3. Determine your braking distance by figuring your speed and multiplying it by itself. Then divide by 20. For example, 30 mph times 30 mph divided by 20 equals 45 feet. This figure is your braking distance.

4. Add thinking distance to your braking distance. For a car traveling at 30 mph, the thinking distance is 30. The braking distance for the same car is 45 feet (see step 3). The result is an overall stopping distance of 75 feet, or 45 feet + 30 feet.

5. Consider that braking distances increase exponentially with increased speed. In addition, visibility plays a great role in braking distances. Nighttime braking is very different from daytime braking. Add in inclement weather and the stopping distance increases.

Tips & Warnings

• Only use braking distance calculations as a general determination of your car's braking distance. By no means does this computation dictate the braking results of every single situation you might face as a driver.