Stopping distances, the two-second rule, wet and icy roads, and contraflows — the Safety Margins topic and its Highway Code rules.
What does this topic cover?
Space management: the two-second rule and its wet/icy multiples, the stopping distance table, aquaplaning, skidding surfaces (wet leaves, diesel spills, loose gravel), and keeping margins in fog, contraflows and queues.
Which Highway Code rules should I revise?
Rule 126 (stopping distances and separation — the single most tested rule), 227–231 (wet weather, ice and snow), 234–236 (fog), and 288–290 (roadworks and contraflow systems, where narrow lanes shrink your margins).
Test yourself on Safety Margins
Free Safety Margins practice questions in the official four-option format, with explained answers and Highway Code references.
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What are the typical stopping distances I must learn?
20 mph: 12 m · 30 mph: 23 m · 40 mph: 36 m · 50 mph: 53 m · 60 mph: 73 m · 70 mph: 96 m. Each splits into thinking distance plus braking distance.
How much do conditions change stopping distances?
Wet roads at least double them (four-second gap); ice can multiply them by ten. Speed is the biggest factor — braking distance grows with the square of speed.
Revise the rest of the syllabus in the 14 DVSA topics directory, or sit the full free mock theory test.