Speed impact braking distance — Alaska Permit Test
Speed impact braking distance on the Alaska permit test — 3 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 is 4 times greater.
People expect twice the speed to mean twice the damage, but the striking power grows much faster than the speed.
The impact is 4 times greater at 40 mph than at 20 mph.
Tripling your speed from 20 to 60 mph makes the impact and braking distance 9 times greater.
At highway speeds the road needed to stop grows far beyond what drivers expect, so small speed gains cost a lot.
Triple the speed from 20 to 60 mph and the impact and braking distance are 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 carries enormous force and stopping takes a huge distance, leaving almost no room for error.
Increase the speed to 80 mph and the impact and braking distance are 16 times greater than at 20 miles per hour.
On the test
How much greater is the impact of a vehicle at 40 mph than at 20 mph?
4 times. People expect twice the speed to mean twice the damage, but the striking power grows much faster than the speed. Alaska Driver Manual, p.33: “The impact is 4 times greater at 40 mph than at 20 mph.”
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.
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- 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 Alaska Driver Manual, published by the Alaska Department of Administration, and against the state code itself. Last checked 2026-10-04.
- src/assets/drivers-manuals/AK.pdf (Alaska Driver Manual, REV.10/2025, Alaska Division of Motor Vehicles, retrieved 2026-09-14 and re-checked 2026-10-04; sha256 pinned in SOURCES.json)
- src/assets/drivers-manuals/AK.pages.txt (the plain pdftotext fixture every citation here was cut from and verified against; sha256 pinned in SOURCES.json)
- https://dmv.alaska.gov/credential-services/drivermanual/ (read 2026-10-04; links the manual)
- https://dmv.alaska.gov/credential-services/instruction-permit/ (read 2026-10-04; states no count or mark)
- https://dmv.alaska.gov/credential-services/your-first-alaska-drivers-license/ (read 2026-10-04; states no count or mark)
- https://www.akleg.gov/basis/aac.asp?media=print&secStart=2.90.010&secEnd=2.90.990 (2 AAC 90, read 2026-10-04; 2 AAC 90.420(h)(2) sets the knowledge test's retest wait and no figure)