The Overtake Behind the Slow Truck
You are driving a sedan on a straight section of the Highlands Highway. Ahead of you is a heavily loaded truck travelling at about 35 km/h. The speed limit is 80 km/h. You have been stuck behind it for several minutes and you are late. The road has a single lane in each direction with a solid white centre line. Visibility ahead is good for about 300 metres. You can see a slight dip in the road about 150 metres ahead where an oncoming vehicle could be hidden. Your passenger urges you to 'just go'. There is a light drizzle and your tyres are about four years old with moderate tread.
1. Should you overtake now? Work through the factors one by one.
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No - this is not a safe overtake. Go through it systematically:
- Road marking: a solid white centre line means overtaking is prohibited. That alone rules it out.
- Sight distance: the dip at 150 metres can hide an oncoming vehicle. You cannot see the whole overtaking distance is clear.
- Speed differential: closing from 35 km/h to 80 km/h and passing a long truck takes time and distance - far more than a glance suggests.
- Surface and tyres: drizzle plus four-year-old tyres with moderate tread means reduced grip and longer braking.
- Pressure: being late and a passenger urging you on are not reasons. They are exactly the conditions in which bad overtakes happen.
The correct action is to stay behind, keep a safe gap, and wait for a legal overtaking opportunity - a broken line with clear sight distance and no oncoming traffic.
2. The truck driver flashes their indicators and slows to let you past. What do you do?
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Treat the signal as a hint, not permission. The truck driver cannot see the road ahead of you as well as you can, and cannot guarantee the far side is clear.
- Do not overtake across a solid line just because the truck slowed. The marking still applies.
- Check for yourself: mirrors, blind spot, oncoming traffic, the dip in the road, and whether the line has become broken.
- Only proceed if you can see the entire overtaking distance is clear and the marking permits it.
- If any of those conditions are not met, stay put. A courtesy flash does not transfer responsibility to the other driver.
3. What following distance should you keep behind the truck, and why does the drizzle matter?
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Use a time gap, not a fixed number of metres. In good conditions, aim for at least a three-second gap; in drizzle, on worn tyres, extend it to four seconds or more.
To check: pick a fixed object the truck passes (a post, a sign) and count 'one thousand, two thousand…' until you reach it. If you arrive before the count finishes, you are too close.
Drizzle matters because:
- It reduces grip, lengthening braking distance.
- It reduces visibility through spray thrown up by the truck.
- Worn tyres channel water less effectively, raising the risk of aquaplaning.
A bigger gap also gives you a better view past the truck, which is what makes a future overtake safe.