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Manitoba Commercial: Speed, following distance and braking

Speed, weight and stopping force, the danger zone, the four-second rule and length-based count, traffic tempo, tailgaters, the 90 m rule, slow-moving vehicles, snubbing and control speed, retarders, ABS and runaway lanes.

  • 14 questions
  • Topic drill
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Speed, following distance and braking · Question 1Score 0/0

Which vehicles may display the slow-moving vehicle sign?

Study reference: MPI Professional Driver's Manual (PDF, Dec. 2025), Ch. 2 Efficient and safe vehicle operation — Speed-weight-distance, Following distance, Traffic tempo, Braking, Engine retarders, Runaway lanes

All 14 questions in this test

Every question and its answer choices. The correct answers and explanations appear when you take the test above.

  1. Which vehicles may display the slow-moving vehicle sign?

    1. Those travelling below the speed limit
    2. Any truck climbing a steep grade
    3. Those travelling at 40 km/h or less
    4. Any vehicle wider than 2.6 m

  2. May engine retarders be used during an MPI road test?

    1. Yes, but only in cities
    2. Yes, they are required on hills
    3. No, they are not allowed on road tests
    4. Only for the Class 1 road test

  3. Your bus is 11.5 m long. Under ideal conditions, what following count should you use?

    1. Four seconds
    2. Five seconds
    3. Two seconds
    4. Three seconds

  4. What is the 'control speed' on a downgrade?

    1. Half of the vehicle's top speed
    2. Speed with rpm just under governed in the chosen gear
    3. The highest speed from which the brakes can still stop the unit
    4. The posted speed limit for the hill

  5. Besides slowing down, how can you shrink your danger zone?

    1. Keep your foot on the accelerator
    2. Turn on your hazard lights and sound the horn
    3. Cover the brake when a hazard may develop
    4. Shift into a higher gear

  6. Your ABS engages during a hard stop. What should you do with the brake pedal?

    1. Keep steady pressure; do not pump it
    2. Use only the trailer hand valve
    3. Pump the pedal quickly and repeatedly
    4. Release it completely, then reapply

  7. If both the weight and the speed of your truck double, how much braking force is needed to stop in the same distance?

    1. Eight times as much
    2. Sixteen times as much
    3. Four times as much
    4. Twice as much

  8. You pass a sign requiring trucks to stop and check brakes. What must you do?

    1. Slow down and check your gauges while moving
    2. Stop only if your brakes feel weak
    3. Use the retarder instead of stopping
    4. Stop, check the brakes and record it in the log book

  9. What does the '8 in 3' rule mean when snubbing the brakes on a downgrade?

    1. Drop eight gears within three seconds
    2. Keep speed 8 km/h below the limit for three km
    3. Brake eight times every three minutes
    4. Slow by about 8 km/h in about three seconds

  10. How should you drive into a runaway lane?

    1. Brake hard and turn sharply into the lane
    2. Shift into neutral and coast into the lane at an angle
    3. Foot off the gas, hold tight, steer straight up
    4. Enter it only after the vehicle has slowed

  11. How can driving much slower than traffic tempo create a hazard?

    1. It forces traffic to use the shoulder legally
    2. Others may tailgate or pass unsafely and cut in
    3. It stops other drivers from changing lanes
    4. It always saves fuel and lowers risk

  12. Outside a restricted speed area, how close may a truck follow another truck or highway bus?

    1. No closer than 90 m
    2. No closer than 30 m
    3. No closer than 150 m
    4. No closer than 60 m

  13. What following distance should an ambulance or van driver keep?

    1. A minimum of three seconds
    2. A minimum of four seconds
    3. A minimum of two seconds
    4. One vehicle length per 15 km/h

  14. On a long grade, the application pressure rises with each snub, from 9 to 20 to 30 psi. What does it signal?

    1. Brake fade; act at once before brakes fail
    2. That the compressor is overfilling the tanks
    3. Normal warming of the brakes on a grade
    4. A faulty gauge that can be ignored

Speed, following distance and braking: key rules to remember

Our summary of what the official handbook says on this topic, in our own words. Read it before or after the practice questions above, then check the original chapter. Read the official chapter ↗

Ch. 2 Speed, weight and the danger zone (pp. 26–27)

  • Doubling weight needs double the braking force; doubling speed needs four times; doubling both needs eight times.
  • The danger zone is the area ahead in which you cannot stop; it grows with speed and on rain, snow, ice or gravel.
  • Slowing down shrinks the danger zone; so does covering the brake when a hazard may develop.

Ch. 2 Following distance and traffic tempo (pp. 28–30)

  • Ambulances and vans: at least a four-second following distance.
  • Buses, trucks and truck-trailers: round the length to the nearest metre and divide by three, but never use less than four seconds.
  • Lengthen the count on rain, snow or ice.
  • Driving faster than traffic tempo removes your stopping space and adds lane changes and fatigue; driving slower invites tailgating and unsafe passing.
  • Large-vehicle drivers depend on outside mirrors; help a tailgater pass and stop gradually.
  • Outside a restricted speed area, regulated vehicles, trucks, highway buses and vehicles towing equipment must not follow within 90 m of each other.
  • On an upgrade with a passing lane, slower vehicles must use the right lane.
  • The slow-moving vehicle sign may be shown only by vehicles travelling 40 km/h or less.

Ch. 2 Braking (pp. 31–33)

  • A level stop normally takes one brake application, eased off at the end.
  • On ice without ABS, lightly release or pump the brakes so the wheels do not lock.
  • Choose a lower gear before a steep downgrade and keep the vehicle in gear; control speed is the downhill speed with rpm just below governed speed.
  • Snubbing: brake to slow about 8 km/h in about three seconds, then release ("8 in 3"); do not let speed rise more than 8 km/h above control speed before snubbing.
  • Where signs require a brake check, you must stop; record the stop in the log book.
  • Engine retarders are used along with snubbing; avoid unnecessary use in cities; choose the gear before the grade; retarders may not be used on road tests.
  • With ABS, brake normally and keep steady pressure; do not pump; ABS cycles up to five times a second.
  • Balanced braking: the foot valve applies trailer brakes at the same pressure as the tractor; the hand valve applies them alone.
  • Over-braking in curves or on ice without ABS can cause a jackknife or skid.
  • Runaway lanes are soft gravel, ash or wood-chip lanes for trucks with failed brakes: foot off the accelerator, hold the wheel tightly, steer straight up the lane.
  • Rising application pressure with each snub on a long grade (for example 9, 15, 20, 30 psi) is a warning of brake fade; act at once.

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