Following Distance on an Icy Highway at Night
It is 11 p.m. in January on Highway 2 north of Red Deer. Temperature is −18 °C and there is light snow. You are doing 100 km/h in the right lane. The pavement looks dark and wet but may be black ice in patches. A semi-trailer is 40 m ahead of you in the same lane, its trailer lights partly obscured by road spray. Its tires are throwing up a fine mist that is freezing on your windshield. You can see taillights of vehicles far ahead but not clearly. Your washer fluid is low and the wipers are starting to streak.
1. Is your current following distance adequate? Justify with numbers and identify the single biggest hazard.
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No - 40 m is far too close. At 100 km/h you cover about 28 m per second. A 40 m gap is only about 1.4 seconds - less than half the 3-second minimum for ideal conditions, and conditions here are far from ideal.
On ice, stopping distance can be several times the dry figure. Dry stopping from 100 km/h is roughly 60–70 m plus reaction distance (~28 m) - call it 90–100 m total. On black ice you might need 200 m or more. A 40 m gap gives you essentially no stopping margin if the semi brakes.
Biggest hazard: the semi's spray freezing on your windshield combined with streaking wipers and low washer fluid - it is degrading your forward vision exactly when you need it most, and you cannot see the road surface to judge ice. The partly obscured trailer lights also shorten the time you'd notice the semi braking.
The fix is to drop back to at least 4–6 seconds (roughly 110–170 m) and get your windshield clear before continuing at this speed; slow down if you can't.
2. The semi's brake lights come on. You are still 40 m back at 100 km/h. What is your sequence of actions, and what is the realistic outcome?
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Sequence:
- Release the accelerator immediately and brake firmly but smoothly - no slamming, to avoid locking/skidding on possible ice and to keep ABS working.
- Steer to maintain your lane; do not swerve into the left lane without checking - there may be a faster vehicle there.
- Brake in a straight line and accept that you may not stop in 40 m.
Realistic outcome: You likely cannot stop in 40 m from 100 km/h on a possibly icy surface. Your best case on dry pavement is ~90–100 m including reaction. So the honest answer is that this gap has already removed your ability to stop - your only remaining options are to reduce impact speed and look for an escape (a clear shoulder or lane) if one exists.
This is the lesson: the decision that mattered was made earlier, when you chose the gap. The correct judgement is to never let yourself be in this position - maintain 4+ seconds at night on winter highways so that when the lights come on, braking is a choice, not a hope.