Excessive speed remains a substantial cause of a collision even where an intervening event (such as a momentary distraction) also contributed, provided the speed impaired the driver's ability to cope with the emergency. The correct counterfactual for assessing causation in speed cases places the hypothetical careful driver in the same position as the actual driver, not at a closer position implied by the slower speed. A three-year licence disqualification for aggravated careless driving causing three deaths is not manifestly excessive where the mandatory minimum is six months.
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