Speed, Following Distance & Overtaking

Adapting your speed to conditions

You must always be able to stop within the distance you can see to be clear ahead. That means reducing your speed below the posted limit for rain, fog, ice, snow, a poor road surface, heavy traffic, poor lighting, or anywhere your view is blocked — a parked truck, a bend, the crest of a hill.

The two-second following distance

The test for a safe gap is simple: could you still stop if the car ahead slammed on its brakes right now? To measure it without guessing, lock onto something fixed up the road — a signpost, a patch of shadow, anything that won't move — and start a slow count the instant the car ahead reaches it: 'twenty-one, twenty-two.' Rolling past that same spot before you're done counting means the gap was never big enough.

As a rough guide in meters: about 25 m at 50 km/h, 35 m at 70 km/h, 45 m at 90 km/h, and 65 m at 120 km/h. In rain, fog, or on a slippery road, double that gap to three or four seconds.

Reaction distance, braking distance, and stopping distance

There's a gap most drivers never think about: the stretch of road eaten up between spotting danger and actually pressing the brake. Call it the reaction distance, or thinking distance — either way, the car doesn't slow down a bit during it, full speed the entire time. Faster driving stretches this gap out: around 15 metres at 50 km/h, 27 metres at 90 km/h, 36 metres at 120 km/h, and none of that even counts the braking itself yet. Anything that dulls a driver's reflexes — alcohol, drugs, exhaustion, a distracted mind — stretches this same gap even further.

Braking distance picks up exactly where reaction distance leaves off: the clock starts the instant the pedal is actually pressed and stops only once the car has come to a complete halt. Speed inflates this number too, and a wet surface always stretches it further than a dry one would. Stack the two distances on top of each other — thinking plus braking — and the sum is what's called stopping distance: everything the car covers between first spotting trouble and finally sitting still.

ABS and tyre condition

What ABS (anti-lock braking system) actually buys you isn't necessarily a shorter stopping distance — it's control. By stopping the wheels from locking and skidding under hard braking, it lets you keep steering the car through an emergency stop instead of sliding wherever momentum takes you. The distance itself may end up about the same as hard braking without it, and even with ABS working perfectly, a wet road still demands more room to stop than a dry one does.

None of that matters, though, if the tyres underneath the car aren't up to the job. The law draws the tread-depth line at 1.6 mm — but treat that number as the bare floor you never want to approach, not a target to coast down to. Beyond tread, pressure matters just as much: keep it at whatever figure the manufacturer specifies, and nudge it a bit higher before a long motorway trip or whenever the car is loaded down with extra weight.

Overtaking versus passing

The word 'overtaking' carries a precise legal meaning, and it hinges entirely on whether the vehicle ahead is moving. A car sitting still — whether parked at the curb or halted in traffic — doesn't trigger overtaking rules at all when you steer around it; that manoeuvre is just passing, a different legal category, and the restrictions this chapter walks through don't apply to it the same way.

Signalling an overtake

Think of it as four beats rather than one motion. Confirm the coast is clear, then signal left — the indicator comes on before you drift, not during. Make the sideways move into the left lane, and once you're settled there, kill the indicator; it's done its job. Pull past the vehicle. Only once it's genuinely behind you does the right indicator come on, clearing the way for you to settle back into your original lane.

Before you overtake

A handful of questions deserve honest answers before you commit to pulling out: Have the mirrors and the blind spot actually been checked, not just glanced at? Has your intention been signalled? Is the road ahead genuinely open all the way through the manoeuvre and back into your lane — enough that nobody coming the other way has to touch their brakes or swerve? Two rules bracket the whole thing regardless of the answers above: the speed limit stays in force even mid-overtake, and pulling out is off the table entirely if someone behind you is already in the process of overtaking you.

Where overtaking is always prohibited

• The vehicle you're eyeing to overtake is doing any of three things near a marked pedestrian or cyclist crossing: closing in on it, easing off its speed, or already stopped there.
• On or approaching a level crossing — this one lifts only in two situations: barriers are fitted, or working signals there are showing the white light that means proceed.
• On or approaching a junction where you're the one who owes priority — either because priority-to-the-right cuts against you or because a give-way situation applies. Your own priority road (B9) status, or a B15 sign covering that exact junction, is what frees you from this one.
• Anywhere the road ahead hides itself from you well enough that certainty about it being clear just isn't possible — a blind bend, the crest of a hill — the ban applies on its own merits, no sign required to trigger it. It steps aside only when the road is laned and you're able to finish the whole overtake without your wheels ever touching the solid line dividing the two directions.
• There's a specific hazard the rules name outright: three vehicles nose-to-tail all overtaking at once, known locally as 'tripleren.' It only becomes illegal, though, in one precise scenario — a car overtaking a car that's overtaking something else. Swap that middle vehicle for a motorcycle or a two-wheeled moped, and the same manoeuvre is perfectly legal on a two-way road. Move the whole scene onto a one-way road with three or more lanes running your direction, and even car-overtaking-car-overtaking-car opens back up.

Overtaking on the right: the exception

Left is the default side for overtaking, full stop — but a traffic jam rewrites that rule. Once several lanes have slowed to a crawl or stopped outright, the side you pick to squeeze past a stopped or crawling vehicle stops mattering. That freedom belongs strictly to queued traffic, though; try the same move on an open road with normal flow and it's still treated as an offence.

Two more doors open for a right-side overtake even without a queue backing things up. Door one: the car ahead has pulled visibly left and flagged a left turn with its indicator — you may slip past on the right, but the strip beyond a solid white edge line and any cycle track are still off-limits for it, while a levelled verge remains fair game. Door two concerns trams specifically: passing one is a right-side job by default, and you only shift to the left when the right-hand gap is genuinely too tight or something fixed — a parked car, an obstacle — is sitting in it, and even then only once it's actually safe to do.

Returning to your lane between two overtakes

Picture a plain single-lane road with one lane running each way — that's the setting where tackling overtakes back-to-back isn't allowed. Clear the first vehicle, tuck back into your own lane the moment it's safe to do so, and only then set your sights on the next one ahead. The one carve-out: two slow vehicles bunched close enough together that squeezing back in between them would itself be the dangerous move — in that specific case, treating both as a single overtake is fine.

That right-lane-in-between rule loosens up considerably once the road itself changes shape. Give a two-way road four or more lanes total, and chaining overtakes together is fine provided you never wander out of the lanes belonging to your own direction. A one-way road drops the requirement entirely, for the simplest reason possible: there's no oncoming traffic to protect against in the first place.

When following a lane is not overtaking

Sometimes what looks like overtaking from the outside isn't legally overtaking at all — it's just lane discipline. Pick whichever lane actually serves where you're headed, and drift ahead of traffic crawling in a neighbouring lane as a side effect, and no overtaking rule has been triggered, provided you're in one of these settings: inside a built-up area, on a one-way road carved into multiple lanes, or on a two-way road carrying four-plus lanes with at least two dedicated to each direction. Simply obeying an F13 or F15 lane-choice sign toward wherever you're going falls under this same umbrella.

F15 — motorway lane-destination sign: straight-down arrows show through lanes, angled arrows show a lane leaving at the next exit

C35 — from this sign to the next junction, no overtaking of a motorcycle, an animal-drawn vehicle, or any vehicle with more than two wheels

Don't mix these two up — C39 has a narrow target, catching only heavy goods vehicles above 3.5 tonnes, while C35 casts a much wider net: it bans overtaking for absolutely every driver, cars included, all the way to the next junction.

C37 — end of the restriction imposed by C35

A C35 restriction ends either at the next junction, or earlier at a C37 sign — whichever comes first. This restriction can also be applied over a longer stretch as a 'zone', with matching start-zone, distance, in-zone repetition, and end-zone signs, in which case it stays in force throughout the zone rather than only until the next junction.

C46 — end of all local restrictions imposed on moving vehicles (cancels C33, C35, C39, and C43 restrictions at once)

This single sign can end several running restrictions — a speed limit, an overtaking ban, or both — at once, and is only used where that end point does not already coincide with a junction or a motorway access point.