Speed and impact — Louisiana Permit Test
Speed and impact on the Louisiana permit test — 5 rules, each with the reason behind it and a question on it while it is fresh.
The rules
When you double your speed from 20 to 40 mph, the impact and the braking distance are 4 times greater.
Speed does not add up in a straight line: a little more speed means a much harder hit and a much longer stop.
When you double your speed from 20 to 40 mph the impact is 4 times greater. The braking distance is also 4 times longer.
Tripling your speed from 20 to 60 mph makes the impact and braking distance 9 times greater.
Three times the speed means nine times the stop, which is why highway crashes are so much worse.
Triple the speed from 20 to 60 mph and the impact and braking distance is 9 times greater.
At 80 mph, the impact and braking distance are 16 times greater than at 20 mph.
At very high speed a crash hits with many times the force, so a small mistake can kill.
Increase the speed to 80 mph and the impact and braking distance are 16 times greater than at 20 mph.
At 60 mph, your stopping distance is greater than the length of a football field.
Picturing a whole football field helps you see how much road you need at highway speed.
At 60 mph, your stopping distance is greater than that of a football field.
Stopping distance depends on your reaction time, weather and road conditions, vehicle weight, brake condition, and tire type and condition.
No single number fits every stop, because a wet road or worn tires add many feet.
The type and condition of the tires
On the test
If you double your speed from 20 to 40 mph, how much longer is your braking distance?
4 times longer. Speed does not add up in a straight line: a little more speed means a much harder hit and a much longer stop. Class D & E Driver's Guide, p.65: “When you double your speed from 20 to 40 mph the impact is 4 times greater. The braking distance is also 4 times longer.”
How this works
Most practice tests hand you a bank of questions and leave the manual somewhere else. This one puts them together.
You read one law and the reason behind it, then answer a question on that law while it is still fresh. Get it right and you move on; get it wrong and you have found the gap while it is cheap to fix, not on the morning of the exam.
Learning one rule at a time, and proving it immediately, is what turns a manual you skimmed into something you actually know — and it makes studying feel like getting somewhere rather than like waiting to find out.
What it costs
- One payment, once — not a subscription. Nothing renews and there is nothing to cancel, for an exam you sit one time.
- Free to start: a 10-question test and the first section of cards. No sign-up and no account.
- Paying opens the rest of the cards, unlimited full-length practice tests, and retests built from exactly the questions you got wrong.
- Every level up to Prepared — 3 tests passed in a row.
- Do the work, fail the real exam, and we refund you.
Where these come from
Every rule here is checked against Class D & E Driver's Guide, published by the Louisiana Department of Public Safety, and against the state code itself. Last checked 2026-10-04.
- src/assets/drivers-manuals/LA.pdf (Class D & E Driver's Guide, DPSMV2052 (R08/25), Louisiana Office of Motor Vehicles, retrieved 2026-09-14; sha256 pinned in SOURCES.json)
- src/assets/drivers-manuals/LA.pages.txt (the plain pdftotext fixture every citation here was cut from and verified against; sha256 pinned in SOURCES.json)
- src/assets/drivers-manuals/LA-exam.html (the OMV's Permits page, https://expresslane.la.gov/omv/drivers/personal-driver-s-licenses/permits/, archived 2026-10-04; the 40-question count)
- https://expresslane.la.gov/omv/resources/driver-manuals/
- https://expresslane.la.gov/omv/drivers/personal-driver-s-licenses/new-licenses/ (read 2026-10-04; "An 80% is the minimum passing score for the knowledge test.")