Right Hook Behind a Turning Tractor-Trailer
You are eastbound at about 40 km/h in a 50 km/h zone on a two-lane street in Dartmouth. A painted bike lane runs along the right side. Ahead of you, a five-axle tractor-trailer has its right signal on and is slowing for the intersection; as it slows it drifts about a metre left, toward the centre line. A cyclist in a helmet and dark clothing is coming up behind you in the bike lane at roughly 25 km/h and will reach the truck's right side at about the same moment you would. The trailer carries a faded 'caution: wide right turns' sticker and a row of small convex mirrors along the cab. On the far corner a pedestrian is waiting to cross. The lane to your left is occupied by a moving car.
1. Why does the truck drift left before turning right, and what does that mean for where your car should be?
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A long wheelbase cannot follow a tight right turn from the right-hand lane, so the driver swings left first to open up the arc; the rear wheels then track inside the path of the front wheels, cutting across the corner and across the bike lane. The space that appears on the truck's right during the swing is not a gap, it is the part of the road the trailer is about to occupy. The safe position for your car is well back, several car lengths behind the trailer, so you are visible in the cab mirrors and completely outside the swept path. Do not move up into the space beside the cab, do not try to squeeze past on the right, and do not assume the driver has seen you. The convex mirrors help the driver, but they do not eliminate the large blind spot along the right side of a five-axle unit.
2. The cyclist is moving up your right side toward the truck. What do you do, and what is outside your control?
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You cannot control the cyclist's decision, but you can avoid becoming part of the problem. If you accelerate to stay alongside, you close the space the cyclist needs and become a third vehicle in a squeeze between a trailer and a bike lane, which is how right-hook collisions happen. The correct move is to slow deliberately, open a large gap, and let the cyclist either stop behind the trailer or pass clear of it before you commit to anything. Hold back far enough that if the cyclist has to swerve or brake, there is room. Do not sound the horn at close range as a first response, since a startled cyclist can swerve into traffic. Your job is to be predictable, visible and slow, and to give the cyclist an escape route rather than taking it away.
3. The lane to your left is occupied and the truck is now mid-turn. Is passing on the left an option?
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No. Passing a heavy vehicle while it is turning is unsafe from either side. On the left you would be moving into the space the cab has just vacated and may swing back into as the driver straightens out, and the moving car already in that lane removes the room anyway. A tractor-trailer's turn also takes far longer than a car's, so the time you would spend alongside is long enough for the driver to lose sight of you. The whole manoeuvre buys a few seconds. Wait behind the trailer until it has completed the turn and its trailer is straight in the new road, confirm the cyclist and pedestrian are clear, then proceed normally. Patience at this intersection costs you perhaps fifteen seconds; the alternative is the classic underride or side-swipe collision.