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Truck handling: blind spots, off-tracking, rear overhang and stopping distance
A truck is taller, longer, wider and heavier than a car, so it has its own dangers. The textbook covers them under "driving to suit the truck's characteristics" and "speed and driving". This page explains each one, why it matters and how to drive.
Last updated: 2026-10-12
At a glance
- 4groups: height, length, width, blind spots
- 9×impact force when speed triples
- 28 mtravelled in 1 second at 100 km/h
- 17 mtravelled in 1 second at 60 km/h
1. Height
- The gap looks longer than it is. From a high seat you see a lot of road, so it is easy to follow too closely. Keep a longer gap.
- You can miss the car right in front. When another truck is further ahead, your eyes lock onto it. It speeds up, you speed up, and you hit the car in between. When the light turns green, check that the car directly ahead has moved.
- Rollovers happen on curves, in turns and in strong wind, especially on bridges. A high load makes a rollover on a curve more likely.
- Underpasses below railways or roads (高架下) have height limits. Know your truck's height and never enter if it is taller. Open-bed trucks can be taller once loaded.
- Keeping too far left on a narrow road can hit signboards or shop eaves.
2. Length: off-tracking (内輪差) and rear overhang
内輪差 (ないりんさ, inner wheel difference) means that in a turn the rear wheels run inside the path of the front wheels. The longer the truck, the larger it is, so a left turn can catch two-wheelers, cyclists and pedestrians on the left, and leaving a customer's site can hit walls or gates.
Some drivers swing right before turning left to avoid this. The textbook says you must not: it still catches two-wheelers, and it can hit an oncoming vehicle (one lane each way) or a vehicle behind in the right lane (two or more lanes). The right way is to keep to the left edge, check the left and left rear, then turn.
リヤ・オーバーハング (rear overhang) is the part of the body behind the rear axle. Because it is long, the tail swings out to the opposite side in a turn and can hit following or oncoming vehicles. Turning right, check the left mirror; turning left, check the right mirror. Pulling out from a bay next to a guardrail, let the car behind pass, then steer gradually.
3. Width: narrow roads and curves
- Meeting an oncoming vehicle on a narrow road: check the left mirror and the safety window (安全窓) for pedestrians and cyclists.
- If it is clear, move left watching for overhead signs, stop and let the other vehicle go first. Do not think "my truck is bigger, they will stop".
- Check that nothing is coming from behind before moving off. A cyclist you blocked may come out on the truck's right.
On a narrow curve with one lane each way, part of the body can cross into the oncoming lane. Watch the centre line in the right mirror.
4. Blind spots (死角, しかく)
- The left side and left rear have areas no mirror shows, and cyclists on the pavement slip into them easily. When turning left, stop before the crosswalk and look left and right.
- The safety window low in the left door exists to remove the blind spot. Do not block it with newspapers or boxes; covering it with a curtain is prohibited, even against the sun.
- A van body (バン型) is blind behind. Before reversing, get out and look; if someone can guide you, use them. Even with a rear camera (バックアイカメラ), check with your own eyes.
5. Speed and stopping distance
| Idea | Key point |
|---|---|
| Impact force (衝撃力) | Proportional to the square of speed: 3 times the speed means 9 times the force. A heavy truck makes it larger still |
| Centrifugal force (遠心力) | Also grows with the square of speed and with weight. A high load can roll over on a curve |
| Stopping distance (停止距離) | = reaction distance (空走距離, until the brakes start to work) + braking distance (制動距離). Braking distance grows roughly with the square of speed |
| Distance per second | About 17 m at 60 km/h and about 28 m at 100 km/h. A short glance at a slip or phone is dangerous |
| Hydroplaning | Fast driving in rain can make steering and brakes stop working (ハイドロプレーニング現象). Slow down in rain |
6. Brake fade on long descents
On a long downhill, using the foot brake too much overheats the linings, friction drops and the brakes stop working. This is フェード現象 (brake fade). Use the engine brake in a low gear and the exhaust brake, and use the foot brake as little as possible. If the gear slips out on a descent, slow down or stop at once with the foot brake, then put it back in gear. An overloaded truck is even harder to slow downhill.
7. Semi-trailers: jackknifing
On a semi-trailer, hard braking or sudden steering can fold the tractor and trailer into a "く" shape (ジャックナイフ現象). It is specific to semi-trailers, not all trucks; it happens more easily at bumps or changes of slope, and when overloaded.
Practise
Free exams 1-3 include items on 内輪差, swinging right before a left turn, rear overhang, the safety window, impact force, brake fade, rear cameras and strong wind. Take the 3 free exams, read the sample questions with answers and learn 内輪差, 死角 and 安全窓.
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FAQ
What is 内輪差?
The inner wheel difference: in a turn the rear wheels run inside the path of the front wheels. The longer the truck, the larger it is, so left turns can catch cyclists and pedestrians on the left.
Should a long truck swing right before turning left?
No. The textbook rules this out: it can catch two-wheelers and hit oncoming traffic or a vehicle behind in the right lane. Keep to the left edge and turn.
Which mirror do I check for the tail when turning right?
The left mirror. The rear overhang (リヤ・オーバーハング) swings to the side opposite the turn; when turning left, check the right mirror.
What is brake fade?
On a long descent, too much foot braking overheats the brakes until they stop working. Prevent it with the engine brake and exhaust brake.
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