A driver switches on the turn indicator at the same instant they begin moving the wheel into the turn. Why is this unsafe?

Why C is correct

A turn signal is communication, and communication that arrives as the event begins arrives too late. Someone who has already committed to passing you, or who has already stepped off the kerb, cannot undo that decision in the half second your indicator takes to light. Signalling early exists so that other people can finish what they have started — completing an overtake, or arresting their own approach — before your path changes. On highway approaches the same logic stretches much further out, because closing speeds mean your intention has to be legible seconds ahead rather than metres.

Why the other options are wrong

A. Indicators are only needed when a vehicle is visible behind you

Waiting for a visible vehicle behind assumes hazards only ever arrive from there. Pedestrians, oncoming left-turners and drivers further back who misread your intentions all depend on the same signal.

B. Turn signals are advisory, much like hazard flashers

Advisory equipment would serve no purpose at all. Turn signals must be fitted to the vehicle, and using them is a legal duty on the driver rather than a courtesy offered to others.

D. It is not unsafe — signalling within the manoeuvre is sufficient

Timing within the manoeuvre is precisely the failure. The signal then announces that you are turning rather than that you intend to, and intent is no longer useful information to anyone nearby.

On the road

A driver waits for a gap to cross traffic from a side street. The car ahead signals only as it swings, far too late for the pedestrian already crossing the near side. Same intention, communicated at a different moment, entirely different result.

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