The Overtake Behind the Truck
You are on a two-lane rural road, one lane each way, posted 100 km/h. You are behind a B-double truck travelling at 90 km/h. The road ahead curves gently to the right, and you can see perhaps 300 m of clear road before the curve hides the rest. There is a broken white centre line. A car has been following you closely for several kilometres. You have been behind the truck for 20 minutes and are becoming impatient; you have an appointment in 40 minutes and are about 15 minutes from town. As you begin to move out to overtake, you see a faint shimmer of headlights far ahead, near the limit of your view around the curve.
1. Is this a safe overtake? Work through the time and distance, not just the view.
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No - this is not a safe overtake, and the faint headlights are the deciding factor.
Rough time and distance:
- To pass a B-double you must cover the truck's length plus your own plus a safety margin. A B-double can be around 25 m; with a 10 m car and margins, you need perhaps 60–80 m of relative travel to complete the pass.
- You are doing 100 km/h against the truck's 90 km/h, so your closing speed is only about 10 km/h, or roughly 2.8 m/s. Covering 70 m of relative distance at that rate takes about 25 seconds.
- At 100 km/h you travel about 28 m per second, so 25 seconds means roughly 700 m of road - far more than the 300 m you can see.
Add the oncoming vehicle: even if it is distant, it is closing at its own speed plus yours. Two vehicles approaching at 100 km/h each close at about 56 m per second. The overtake would put you in that closing path for most of its duration.
The broken centre line permits overtaking only when it is safe, not whenever it is legal to cross.
2. What role does the following car play, and what role does your impatience play?
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The following car removes your escape route. If you pull out and then abort, you must brake and return to the left lane - but a closely following car may be in the space you need, or may follow you out, compounding the situation. It also raises the temptation to 'commit' once you have moved out, which is exactly the wrong instinct. A safe overtake requires that you can abort cleanly.
Impatience is the more dangerous factor because it distorts the decision. Twenty minutes behind a truck and a looming appointment create a strong pull to accept a marginal gap. Recognise the symptoms:
- You are looking for reasons to go rather than reasons not to.
- You are treating 'I have waited long enough' as evidence of safety.
- The 15-minute buffer is being spent on stress rather than on a plan.
The correct reframe: the appointment is 15 minutes away and you are 40 minutes out. Overtaking unsafely might save 30 seconds; a crash or a head-on would cost the appointment entirely. The right response to impatience is to create time - accept the delay, and if needed call ahead - not to buy time with risk.
3. What should you actually do now, and what would make the overtake acceptable later?
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Now: stay in your lane, ease off slightly to increase your gap to the truck so you can see further past it, and let the oncoming vehicle pass and the curve open up. Do not begin the manoeuvre on a shimmer of headlights.
What would make it acceptable:
- A clear, straight section with sight distance comfortably greater than the distance you need to complete the pass - not merely 'no car visible right now'.
- No oncoming traffic confirmed, not assumed, and no side roads, crests, or bends within the overtaking zone.
- A sufficient speed advantage: if you must exceed the limit substantially to pass, the gap is not there. Better to wait for a section where you can pass decisively.
- Space to abort: no closely following vehicle that would block your return.
- A signal, a mirror and blind-spot check, and a smooth move out and back.
If none of these align before town, the correct outcome is to stay behind the truck. Arriving a few minutes late is the acceptable cost.