Why it matters: The three-colour traffic light: green, yellow, red — and its limits

Misjudging yellow is dangerous in both directions: braking too late causes an emergency stop and a rear-end collision behind you; proceeding too eagerly through a light that has been yellow too long costs you a fine and can leave you stranded mid-junction just as the light turns to allow crossing traffic through at a busy roundabout in Alkmaar.