UK driving terms explained

The theory test uses words that nobody uses anywhere else. Here is what each one means, why it matters on the road, and the practice questions that test it.

Anti-lock braking system (ABS) A system that stops the wheels locking under heavy braking so you can still steer — not a shorter stopping distance. 25 practice questions → Aquaplaning Riding on water rather than road, when the tyres cannot clear standing water fast enough. 8 practice questions → Blind spot The area around your vehicle that none of your mirrors show you, which is why a shoulder check exists. 38 practice questions → Box junction Criss-cross yellow lines you may only enter when your exit is clear — with one exception for turning right. 6 practice questions → Buffer lane A lane kept deliberately empty in high winds, usually on an exposed bridge, so a vehicle blown sideways has somewhere to go instead of hitting traffic. 4 practice questions → Bus lane A lane reserved for buses during the hours shown on the sign — and open to everyone outside them, unless the sign shows no hours at all. 21 practice questions → Catalytic converter An exhaust component that converts the most harmful gases into less harmful ones. 6 practice questions → Clearway A road where you must not stop at all — not to wait, not to set down, not for a moment. 10 practice questions → Coasting Rolling with the clutch down or out of gear, which quietly removes most of your control. 11 practice questions → Contraflow A stretch where traffic runs on the opposite side from normal, usually to keep a road open through roadworks. 21 practice questions → Crawler lane An extra lane on a long uphill gradient, so slow heavy vehicles do not hold up everything behind them. 10 practice questions → Cycle lane A marked lane for cyclists: a solid white line means keep out during its hours, a broken line means avoid it if you can. 19 practice questions → Dipped headlights The normal night setting: enough light to drive by, aimed low enough not to blind anyone. 56 practice questions → Dual carriageway Two carriageways separated by a central reservation — which is what makes it dual, not the number of lanes. 84 practice questions → Engine braking Letting the engine slow the vehicle through the gears, instead of making the brakes do everything. 11 practice questions → Fifth wheel The coupling that joins an articulated tractor unit to its semi-trailer, and carries part of the trailer’s weight. 10 practice questions → Fog lights Extra-bright lights for seriously reduced visibility — and a dazzle hazard the moment the fog lifts. 33 practice questions → Hard shoulder The strip at the far left of a motorway, for emergencies only — except where a smart motorway is running traffic on it. 97 practice questions → Hazard warning lights All four indicators flashing together — a warning that you are an obstruction, not a licence to park where you like. 69 practice questions → Humpback bridge A steeply arched bridge that hides the road beyond it — and can ground a long vehicle on the crown. 8 practice questions → Level crossing Where a road crosses a railway on the flat — the one place where being slow to clear is catastrophic rather than inconvenient. 30 practice questions → Maximum authorised mass (MAM) The heaviest a vehicle is legally allowed to be once it is loaded — the vehicle itself plus fuel, driver, passengers and load. 28 practice questions → Mini-roundabout A roundabout painted on the road: the same give-way-to-the-right rule, in much less space and with far less time. 11 practice questions → Mirrors, signal, manoeuvre The routine behind most of the judgement questions: look, tell people, then act — in that order. 8 practice questions → MOT test The annual roadworthiness and emissions test, required once most vehicles reach three years old. 34 practice questions → National speed limit The white circle with a black diagonal does not mean one number — it means the limit for that road and your vehicle, which are not the same thing. 127 practice questions → Pelican crossing A light-controlled crossing the pedestrian starts, with a flashing amber phase that means give way if anyone is still crossing. 22 practice questions → Puffin crossing A crossing with sensors that watch the pedestrians, so the lights hold until the crossing is actually clear. 8 practice questions → Red route Red lines instead of yellow, with stricter rules: a double red line means no stopping at any time. 11 practice questions → Reflective road studs The coloured studs in the road surface that tell you, in the dark, which lane you are in and what is beside you. 14 practice questions → Retarder An auxiliary braking system on heavy vehicles that slows the vehicle without using the service brakes. 19 practice questions → Skidding Loss of grip — and almost always something the driver did, rather than something the road did. 39 practice questions → Slip road The road you join or leave a motorway by — and the place to get your speed right before you arrive. 32 practice questions → Stopping distance Everything between seeing a hazard and being stopped: your reaction distance plus the distance the brakes need. 40 practice questions → Tachograph The device that records a professional driver’s driving time, breaks and speed — and the evidence if the limits are broken. 52 practice questions → Tailgating Following too closely — which removes your own reaction room and does nothing to the driver in front. 11 practice questions → Third party insurance The legal minimum: it pays for the harm you cause to other people, and nothing at all for your own vehicle. 27 practice questions → Toucan crossing A light-controlled crossing where cyclists may ride across alongside pedestrians — "two can" cross. 10 practice questions → Tram A vehicle running on rails in the street: it cannot steer, it is nearly silent, and it usually has priority. 25 practice questions → Two-second rule A way of checking your following gap without measuring anything: two seconds in good conditions, double it in the wet, far more on ice. 11 practice questions → Tyre tread depth The legal minimum for cars is 1.6 mm across the central three-quarters, all the way round. 12 practice questions → Zebra crossing Black and white stripes with flashing yellow beacons, where pedestrians get priority once they have stepped on. 25 practice questions →