Left turn across a cyclist in the blind spot
A driver is in a 12.5 m rigid truck, 2.55 m wide, heading east in the left lane of a four-lane road at 25 km/h, approaching a signalised intersection where they intend to turn left. A short left-turn slip lane and a kerbside cycle lane run along the left of the traffic lane; there is no bike box. About 8 m before the turn the driver checks the left convex mirror and sees a cyclist who has come up the inside and is now level with the truck's rear axle. The light ahead turns amber, the truck is 20 m from the stop line, the speed limit is 50 km/h, there is a car close behind, and a pedestrian is waiting at the corner.
1. Why is the cyclist in a dangerous position, and why is the cab clearing them not the point?
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The cyclist is level with the rear axle, which is where the truck's left blind spot is worst: the convex mirror may show them one moment and lose them the next as the cab rotates and the mirror angles change. The danger is not the cab clearing the cyclist; it is the back of the truck. A 12.5 m rigid off-tracks on a left turn, so the rear wheels and tail swing sweep inside the path of the front. Turning left now would cut across the cyclist's line and put the rear wheels through the space they are occupying. The amber light adds pressure to hurry, but at 25 km/h and 20 m from the line the truck can still stop.
2. What should the driver do right now?
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Ease off, do not accelerate to beat the amber, and do not swing left. Let the cyclist come through and clear the front corner before the truck turns. If the light is red by the time the truck reaches the line, stop and wait; the cyclist gets a head start and the turn is completed after they have gone. Keep the left indicator on so the cyclist knows what is intended, check the left mirror again before moving, and expect the car behind to stop rather than assume it will. If the turn has already started, stop and let the cyclist pass rather than completing a turn that closes the gap on them.
3. How should this driver approach the same turn next time?
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Check the left mirror before the slip lane, move as far left as is legal early and at low speed, and repeat the left convex mirror check before turning. The rule to hold on to is: never overtake a cyclist and then immediately turn left across them. Either stay behind or be fully ahead before the turn. On routes with a kerbside cycle lane, plan for riders coming up the inside whenever traffic slows, treat the mirror check as a two-stage habit rather than one glance, and report the location if the slip lane geometry keeps putting riders in the blind spot so the operator can raise it with the road controlling authority.