When you’re driving behind a large truck, you should leave more space than you would behind a car, typically at least a 4‑second gap in good conditions and more as speed or risk increases. This extra distance lets you see the road ahead and gives you time to brake if the truck stops suddenly.

Core rule of thumb

  • In normal, dry conditions on open roads, aim for:
    • At least 4 seconds of following distance behind a large truck at highway speeds.
    • Increase to 5–6+ seconds if:
      • You’re going faster
      • Traffic is dense
      • You feel boxed in or visibility is reduced
  • Use the “seconds, not meters” approach:
    1. Pick a fixed object ahead (sign, pole, bridge).
    2. When the back of the truck passes it, start counting: “one‑thousand‑one, one‑thousand‑two…”.
    3. Your vehicle should not reach that object until at least “one‑thousand‑four”.

Why trucks need more space

  • Trucks are very heavy, so they need a longer stopping distance than cars at the same speed.
  • Sitting close behind a truck:
    • Blocks your view of traffic and hazards ahead.
    • Puts you in a “no‑see” zone where the truck driver may not know you’re there.
    • Increases the risk of underride (a car sliding under the truck’s rear) if there’s a sudden stop.

When to leave even more distance

Increase your following distance beyond 4 seconds (often 6–8 seconds) when:

  • It’s raining, foggy, icy, or the road surface is poor.
  • You’re going downhill (both you and the truck will need more space).
  • You’re tired, distracted, or unfamiliar with the road.
  • The truck is carrying heavy or unstable loads (logs, cars, tankers, etc.).

A simple safety mindset: if you’re close enough that you can’t see the truck’s mirrors clearly or can’t see past the truck, you’re too close —back off until you have a generous time gap.