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Idaho driving lesson · Weather & Special Conditions

Winter driving and snowplows

A 4-minute lesson from the Idaho course. Read the rules and examples, follow the handbook page references, and check your understanding before you move on.

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Read time
4 minutes
Course unit
Weather & Special Conditions
Checkpoint questions
6
Source pages
109, 110, 113, 114, 115

On slippery roads, the keys to safety are slower speeds, gentler stops and turns, and longer following distances. Idaho winters can be severe, especially in the mountains, so be ready to get stuck.

2 car lengths

Stay this far behind a snowplow for every 10 mph you drive

Handbook p. 110 ↗

Around snowplows:

  • Don't pass unless absolutely necessary, and only when you can clearly see the road ahead
  • Never pass on the side where the plow is spraying snow; it can knock you out of control
  • Don't cut back in right in front of a plow; its blades can be hard to see
  • Don't brake suddenly in front of a plow; it can't stop as quickly as you
  • Abandon your car only if absolutely necessary, and leave it as far off the road as possible
Handbook p. 110 ↗

Winter driving tips:

  • Keep lights, tires, brakes, wipers, defroster, and radiator in top condition
  • Don't drive until windows are defrosted and clean; use non-freezing washer fluid
  • Don't use cruise control on wet or icy roads
  • Start slowly to test steering and braking; press the gas gently to avoid spinning tires
  • Start slowing at least three times sooner than normal for turns and stops
  • Avoid sudden steering and pump brakes gently (steady pressure with anti-lock brakes)
  • Use tire chains on very slippery roads
Handbook p. 113 ↗

Know the rule

Ice forms sooner and stays longer on bridges and overpasses, which are exposed underneath and get no ground warmth. Snow and ice also last longer in shaded spots.

Handbook p. 113 ↗

Know the rule

Studded snow tires may be used only from October 1 to April 30; ITD sometimes adjusts the dates for weather.

Handbook p. 114 ↗

Winter emergency kit:

  • Flashlights with extra batteries; a first aid kit; a pocket knife
  • At least one blanket or sleeping bag; extra gloves, socks, and a wool cap
  • A small sack of sand or cat litter for traction; a small shovel
  • Bottled water; energy bars or other non-perishable food
  • Booster cables; emergency flares; waterproof matches or lighter
  • A brightly colored scarf to attract attention; a map; a phone charger
Handbook p. 114 ↗

Know the rule

If you run the engine for heat, make sure the exhaust pipe is clear of snow. Tie a bright cloth to the antenna for snow crews.

Handbook p. 114 ↗

Know the rule

Tell someone your departure and arrival times, route, and where you'll stay. If stranded while heavy snow is falling, stay with your vehicle: most deaths happen when people leave, get lost, and freeze.

Handbook p. 115 ↗

Know the rule

For medical emergencies where roads haven't been plowed, call local or state police; they work with search and rescue and ITD.

Handbook p. 115 ↗

Put it into practice

You're driving 40 mph behind a snowplow spreading sand. Stay at least 8 car lengths back (2 for every 10 mph). If you must pass, do it only with a clear view ahead and never on the side where it's throwing snow.

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.

When following a snowplow truck, you should remain how many car lengths back per 10 mph of speed?
  1. 2 car lengths
  2. 3 car lengths
  3. 1 car length
  4. 4 car lengths

Answer: 2 car lengths

Stay two car lengths back for every 10 mph while following a plow.

Handbook p. 110 ↗
On slippery roads, you should start slowing down:
  1. only after skidding begins
  2. at least three times sooner than normal
  3. only slightly sooner than normal
  4. the same as on dry roads

Answer: at least three times sooner than normal

Begin slowing at least three times earlier than usual on slick roads.

Handbook p. 113 ↗
Ice tends to form first and linger longest on:
  1. wide intersections
  2. open straightaways
  3. freshly plowed lanes
  4. bridges and overpasses

Answer: bridges and overpasses

Bridges and overpasses lose ground warmth and ice up first.

Handbook p. 113 ↗
In some years, who may adjust the dates when studded snow tires are allowed?
  1. the Idaho Transportation Department
  2. each county sheriff
  3. the Idaho State Police
  4. local city councils

Answer: the Idaho Transportation Department

Studded tires are allowed October 1 to April 30, but some years ITD adjusts the dates due to weather.

Handbook p. 114 ↗
If your car breaks down in heavy snow, you should generally:
  1. leave the vehicle and wait nearby
  2. stay with your vehicle
  3. abandon it and flag down traffic on foot
  4. walk to find help immediately

Answer: stay with your vehicle

Most winter deaths occur when people leave their vehicle and get lost.

Handbook p. 115 ↗
It's safe to pass a snowplow on the side where it's actively spraying snow.
  1. True
  2. False

Answer: False

Never pass on the side where the plow is spraying snow.

Handbook p. 110 ↗
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