Adjusting speed for roads, weather and sight distance

Key points

1. Stopping from 60 mph takes over three times the distance needed at 30 mph.

   Source: Handbook p. 59

   “stopping at 60 mph does not take twice the distance as it takes at 30 mph, but over three times the distance.”
   Montana Driver Manual, Handbook p. 59

2. On a wet road slow about 10 mph; on packed snow cut your speed in half; on ice slow to a crawl.

   Source: Handbook p. 60

   “On a wet road, reduce your speed about 10 mph. On packed snow, cut your speed in half. Use snow tires or chains when the road has snow on it. On ice, you must slow to a crawl.”
   Montana Driver Manual, Handbook p. 60

3. Studded tires are not allowed June 1 through September 30.

   Source: Handbook p. 60

   “Studded tires are not allowed June 1 through September 30.”
   Montana Driver Manual, Handbook p. 60

4. Tires can start hydroplaning above about 35 mph on a wet road, and in heavy rain can lose all traction at about 50 mph.

   Source: Handbook p. 60

   “When the road is wet, most tires have good traction up to about 35 mph. However, as you go faster your tires will actually start to float on a film of water. This is called hydroplaning. In a heavy rain, your tires can lose all traction with the road at about 50 mph.”
   Montana Driver Manual, Handbook p. 60

5. If your tires lose traction on water, ease off the gas and keep the wheel straight.

   Source: Handbook p. 60

   “Ease your foot off the gas pedal ■ Keep the steering wheel straight”
   Montana Driver Manual, Handbook p. 60

6. In a skid, stay off the brake, ease off the gas and steer where you want to go.

   Source: Handbook p. 60

   “Stay off the brake - Until the vehicle slows, your brakes will not work and could cause you to skid more. ■ Take your foot off the accelerator to slow and look where you want to go.”
   Montana Driver Manual, Handbook p. 60

7. At 50 mph it can take about 400 feet to react and stop; at 30 mph about 200 feet.

   Source: Handbook p. 63

   “At 50 mph, it can take about 400 feet to react to something you see and bring your vehicle to a stop. That is about the length of a city block. ■ At 30 mph, it can take about 200 feet to stop.”
   Montana Driver Manual, Handbook p. 63

8. If heavy rain, snow or fog limits you to about 200 feet of view, you cannot safely go faster than 30 mph.

   Source: Handbook p. 63

   “you may not be able to see much more than 200 feet ahead. When you cannot see any farther than that, you cannot safely drive faster than 30 mph.”
   Montana Driver Manual, Handbook p. 63

9. Use the four second sight distance rule: if you reach a fixed object before counting to four, slow down.

   Source: Handbook p. 64

   “If you reach the object before you finish saying “four-one-thousand,” you need to slow down. You are going too fast for your sight distance.”
   Montana Driver Manual, Handbook p. 64

10. If you see an animal, slow down and be ready to stop. If you cannot avoid it, do not swerve sharply.

    Source: Handbook p. 61

    “If you see an animal, slow down and be prepared to stop. If there isn’t time to stop or avoid the animal, do not swerve sharply.”
    Montana Driver Manual, Handbook p. 61

Numbers to know

3 questions from the Montana practice test

1. 1. If your tires lose traction on standing water, what should you do first?

   1. Ease your foot off the gas pedal
   2. Brake hard while turning toward the shoulder
   3. Turn sharply toward the nearest lane
   4. Shift into a higher gear and accelerate
   Show answer

   Ease your foot off the gas pedal. When water separates the tires from the pavement, lifting your foot from the accelerator helps the vehicle slow without adding a sudden braking or steering demand. The manual also advises keeping the wheel straight and postponing a stop or turn until the tires grip again. Hard braking while turning can worsen the loss of control, and acceleration keeps the tires moving across the water film. Use the sensation of a light or unresponsive steering wheel as your cue to ease off the gas and wait for traction to return.

2. 2. What does hydroplaning describe?

   1. A tire losing air after striking a pothole
   2. Tires floating on a film of water and losing contact with the road
   3. A vehicle overheating while driving through rain
   4. A controlled braking method for slick pavement
   Show answer

   Tires floating on a film of water and losing contact with the road. Hydroplaning occurs when speed on a wet roadway causes tires to float on a film of water rather than maintain normal contact with the pavement. That loss of traction can make steering feel ineffective and can become complete in heavy rain, especially with worn tires. A puncture, overheating, or deliberate braking technique describes a different problem. The strongest prevention cue is speed: slow down in rain or whenever the road is wet, then avoid abrupt steering and braking if traction begins to disappear.

3. 3. If heavy rain, snow, or fog limits visibility to about 200 feet, how fast may a driver safely travel?

   1. The posted limit, regardless of what can be seen
   2. No faster than 30 mph
   3. At least 50 mph to clear the weather quickly
   4. Any speed below 70 mph if headlights are on
   Show answer

   No faster than 30 mph. The manual says that when heavy rain, a snowstorm, or thick fog limits visibility to about 200 feet, a driver cannot safely travel faster than 30 mph. Headlights improve visibility to others but do not make an unsafe speed acceptable. The posted limit and a high-speed escape strategy ignore sight distance. If the downpour prevents safe driving at all, pull off in a safe place and wait for conditions to improve.

Source: the Montana Driver Manual, Chapter 5: How to Drive Safely. This lesson is a plain English summary, not the law itself; where it differs, the manual and the statute govern. Last checked 2026-09-27.