Roadwise States Louisiana Driving lessons Stopping distance & speed Louisiana driving lesson · Space, Speed & Stopping
Stopping distance & speed A 3-minute lesson from the Louisiana course. Read the rules and examples, follow the handbook page references, and check your understanding before you move on.
Read time 3 minutes
Course unit Space, Speed & Stopping
Checkpoint questions 6
Source pages 69, 70 Stopping takes three steps: seeing the hazard, reacting to it, and braking. The faster you go, the more ground each step covers, and braking distance and impact grow with the square of your speed.
Perception distance How far you travel from when your eyes see a hazard until your brain recognizes it. Average perception time for an alert driver: 3/4 second to 1 second.
Handbook p. 69 ↗ Reaction distance How far you travel after recognizing the hazard before you hit the brakes. Average reaction time is 3/4 to 1 second: 55 feet at 50 mph.
Handbook p. 69 ↗ Braking distance How far you travel while braking. At 50 mph on dry pavement with good brakes, about 158 feet.
Handbook p. 69 ↗ 268 feet Minimum total stopping distance at 50 mph in ideal conditions
Handbook p. 70 ↗ Know the rule
At 60 mph, your stopping distance is longer than a football field.
Handbook p. 70 ↗ Your stopping distance depends on: Your own reaction time Weather and road conditions The weight of the vehicle The condition of the brakes The type and condition of the tires Handbook p. 70 ↗ Know the rule
Mental and physical conditions, visibility and the hazard itself can greatly lengthen perception distance.
Handbook p. 69 ↗ Know the rule
High speeds greatly increase crash severity and stopping distance; slowing down reduces braking distance.
Handbook p. 70 ↗ Put it into practice
You speed up from 20 to 40 mph. It feels like twice as fast, but your braking distance and the force of any impact are four times greater.
Check your understanding Read the question, decide on an answer, then open it to check the explanation. These are Roadwise study questions based on the source handbook.
What is the approximate minimum total stopping distance at 50 mph on dry pavement? 268 feet 100 feet 450 feet 55 feet Answer: 268 feet
Total stopping distance at 50 mph, combining perception, reaction, and braking, is about 268 feet.
Handbook p. 69 ↗ At 50 mph, about how far does a vehicle travel during the driver's reaction time, before braking begins? 10 feet 55 feet 158 feet 268 feet Answer: 55 feet
Reaction distance at 50 mph is about 55 feet, separate from the braking distance.
Handbook p. 69 ↗ At 50 mph on dry pavement with good brakes, about how far does braking distance alone add? 55 feet 268 feet 158 feet 20 feet Answer: 158 feet
Braking distance at 50 mph adds about 158 feet on top of perception and reaction distance.
Handbook p. 69 ↗ If you double your speed from 20 to 40 mph, how much greater is the impact and braking distance? 2 times greater 8 times greater The same 4 times greater Answer: 4 times greater
Because impact force relates to speed squared, doubling speed quadruples the impact and braking distance.
Handbook p. 70 ↗ If you triple your speed from 20 to 60 mph, how much greater is the impact and braking distance? 9 times greater 3 times greater 6 times greater 12 times greater Answer: 9 times greater
Tripling speed increases impact and braking distance by a factor of 9, since force scales with the square of speed.
Handbook p. 70 ↗ The average driver's reaction time to a hazard is about: 3 to 4 seconds Less than 0.1 second 3/4 to 1 second 5 seconds or more Answer: 3/4 to 1 second
The handbook states average perception and reaction time is 3/4 to 1 second.
Handbook p. 69 ↗ Previous lesson Looking to the sides, rear & mirrors Next lesson Following distance: the 3- and 4-second rules More in Space, Speed & Stopping About the source Roadwise’s Louisiana course uses the driver handbook edition supplied with this study pack. This lesson cites source pages 69, 70. The linked PDF is a third-party mirror of the handbook, rather than a government-hosted page.
Open the handbook source PDF · View the source edition
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