Merging Onto a Motorway Behind a Slow Truck
You are entering a 110 km/h motorway via an on-ramp that becomes an acceleration lane. Your car is at 80 km/h. Ahead in the left lane is a B-double truck travelling at about 95 km/h, and its rear trailer is roughly level with the end of your acceleration lane. Behind the truck, a gap of about three car lengths is closing because a sedan is overtaking in the right lane and will pull back into the left lane shortly. The acceleration lane is ending in about 150 metres. It has been raining and there is spray from the truck. You have a probationary licence and must display P plates.
1. Should you accelerate to merge ahead of the truck or adjust to merge behind it? Give your reasoning.
Read the worked answer
You should adjust to merge behind the truck, not try to beat it.
The truck's rear trailer is already level with the end of your lane, so accelerating to get ahead would mean passing a B-double in a short distance while the lane runs out. A heavily loaded truck at 95 km/h will not slow to let you in, and cutting in front of it leaves almost no gap - a truck needs far more distance to stop than a car, so pulling in close ahead is dangerous.
The closing gap behind the truck is the deciding factor. A sedan is overtaking and will soon return to the left lane, so the space behind the truck is temporary. The safest plan is to ease off, let the truck pass, match speed to the traffic flow, and merge into the gap behind it once the sedan has settled. Merging behind is a controlled, low-risk move; forcing in ahead is a gamble.
2. What speed should you aim for as you merge, and why is matching traffic speed important here?
Read the worked answer
Aim to merge at close to the speed of the traffic already in the lane - around 95–100 km/h - once you have a clear gap behind the truck. Merging far slower than surrounding traffic creates a speed difference that other drivers cannot easily judge.
You are currently at 80 km/h with about 150 metres of lane left. Use that distance to build speed smoothly so that when the gap opens you are travelling at a comparable speed, then slot in. Do not stop at the end of the acceleration lane; stopping there with traffic approaching at 95 km/h is extremely hazardous.
The wet surface and spray mean you should also leave a larger following distance once merged, and avoid sitting in the truck's spray where your visibility is reduced.
3. The sedan in the right lane is overtaking. How does that affect your merge and your observation routine?
Read the worked answer
The sedan's move means the left-lane gap behind the truck is not yet available - it will open only after the sedan completes its overtake and settles back. You must not merge into that space while the sedan is still alongside or moving across.
Observation routine: check your right mirror and blind spot for the sedan, watch the truck's indicators and position, and keep monitoring the gap behind the truck. Signal your intention early so surrounding drivers know your plan. Only when the sedan has clearly completed its lane change and the gap is stable should you accelerate into it.
If the gap does not open before the lane ends, slow and prepare to stop or yield at the end of the acceleration lane rather than forcing a merge - but with 150 metres and a closing gap, easing off behind the truck should let you merge safely.