Dual Carriageways: Rules & Driving Test Guide (Skill 22)
Dual carriageways are included in some driving tests, and they are present on most driving routes taken in the weeks and months after passing. Understanding how to use them correctly is not just a test skill — it is a core road safety competency that affects every journey on a major road.
DVSA Skill 22 covers the full sequence: joining from a slip road, travelling at speed with correct lane discipline, overtaking safely, and leaving via a deceleration lane. Each element has specific technique that is assessed independently.
What Examiners Look For
On a dual carriageway, the examiner assesses whether you can match the speed of flowing traffic when joining. Joining at 30mph when the carriageway is flowing at 70mph creates a severe hazard for following traffic. You are expected to use the entire length of the slip road to build speed and join at a speed that is compatible with the traffic already on the carriageway.
Lane discipline is one of the most frequently faulted behaviours on dual carriageways. The examiner expects you to remain in the left lane except when overtaking. The moment you finish passing a vehicle, you should signal and return to the left lane. Remaining in the right or middle lane without overtaking is a specific Highway Code offence and a driving test fault.
Overtaking technique is assessed on the Mirror-Signal-Manoeuvre sequence. Check interior mirror, check right door mirror, check right blind spot, signal, move out, pass, check left mirror, signal left, return to lane. Each element must be present and in sequence.
Leaving correctly means using the deceleration lane for decelerating, not the carriageway itself. Braking hard in the left lane before the deceleration lane startles following traffic. The examiner wants to see you signal early, move into the deceleration lane at the countdown markers, and then reduce speed progressively.
The 5 DVSA Levels for Dual Carriageways
Level 1: Introduced
The pupil understands the layout of a dual carriageway — the central reservation, the lanes, slip roads, and deceleration lanes — and can identify them. They are not yet ready to drive on one.
Level 2: Helped
The pupil joins and leaves with active instructor support. They may need coaching through the acceleration phase, reminders about lane discipline, or intervention on the MSM sequence for overtaking.
Level 3: Prompted
The pupil drives on dual carriageways with occasional verbal prompts — “build your speed,” “you can return to the left lane now,” or “check your blind spot before moving right.” The overall approach is correct.
Level 4: Independent
The pupil joins, travels, overtakes, and leaves without instructor input. Lane discipline is maintained automatically. Errors are minor and self-corrected.
Level 5: Reflection
Test-ready standard. The pupil reads traffic flow before joining and times entry naturally. Lane discipline is automatic. They can explain every decision and anticipate upcoming exits well in advance.
Dual Carriageway Technique in Full
Understanding the Road Layout
A dual carriageway has two or more lanes in each direction, separated by a central reservation. Unlike a motorway, it may have at-grade junctions, roundabouts, and lower-speed sections. The speed limit is usually 70mph but can be 50mph or 60mph — always check the signs.
Do not confuse a dual carriageway with a motorway. Learner drivers can use dual carriageways but could not legally drive on motorways before the 2018 rule change allowing it with an ADI.
Joining: Using the Acceleration Lane
The slip road is your run-up. Use every metre of it. A common error is panicking and braking on the slip road when you see traffic — this makes the join far more dangerous because you arrive at the carriageway at a very low speed.
Assess the traffic in the left lane as you travel down the slip road. Identify a gap you can slot into. If the gap is clear, aim to arrive at that gap at the speed of the carriageway. If the gap is closing, adjust your speed slightly to slot in behind the vehicle.
Signal right before the give-way line to communicate your intention to join. Give way to traffic already on the carriageway — you do not have right of way. But do not stop on the slip road unless you absolutely must; stopping on the acceleration lane is dangerous.
Lane Discipline While Travelling
Default position: left lane. The only reason to be in the right lane is to overtake. Once you have overtaken, return to the left lane. If there is a long queue of vehicles to overtake, you may remain in the right lane while passing them — but the moment the left lane is clear alongside you, you should move back.
On a three-lane dual carriageway, the rightmost lane is for overtaking vehicles in the middle lane. The middle lane is for overtaking vehicles in the left lane. Many drivers incorrectly treat the middle lane as a default — this is middle-lane hogging and is both an offence and a driving test fault.
Overtaking on a Dual Carriageway
The MSM sequence: Mirror (interior, right door), Signal (right), Manoeuvre (check blind spot, move out, pass, check left mirror, signal left, return to left lane).
Match your speed to the vehicle you are overtaking as you pull alongside — do not slow down and sit beside them. Slow vehicles should be passed promptly and cleanly. After returning to the left lane, cancel your left signal.
Do not overtake where the right lane is blocked, where there are upcoming exits, or where traffic is joining from a slip road on the right.
Leaving: The Deceleration Lane
Begin preparing for your exit well before the countdown markers (300m, 200m, 100m before the exit). Check mirrors, signal left, and move to the left lane in good time.
At the countdown markers, move into the deceleration lane. You should still be at or near dual carriageway speed as you enter the deceleration lane — you reduce speed in it, not before it. Braking from 70mph to 30mph on the carriageway itself is dangerous.
Once in the deceleration lane, brake progressively and adjust your speed for the road type you are joining — a roundabout requires a much lower speed than a continuation of a 40mph road.
Common Mistakes and How to Avoid Them
| Mistake | Why It Happens | The Fix |
|---|---|---|
| Joining at too low a speed | Fear of high-speed traffic; braking on the slip road | Trust the acceleration lane; practise building to 60mph+ on the slip road with instructor guidance |
| Staying in the right lane after overtaking | Not noticing the left lane is clear; laziness | Make returning to the left lane part of the MSM routine — signal left as soon as you complete the pass |
| Braking before the deceleration lane | Wanting to slow down gradually from a long distance | Maintain speed until you reach the countdown markers, then use the deceleration lane for braking |
| Forgetting the blind spot before moving right | Rushed MSM sequence | Verbalise the sequence: “mirror, mirror, blind spot” before every lane change |
| Panic-stopping on the slip road | Low speed and a gap disappears | If a gap closes, adjust speed slightly to find the next gap — keep moving forward |
Practice Tips
Drive on quiet dual carriageways first. A rural dual carriageway with light traffic is a very different environment to a busy urban one. Begin on quieter roads and build up to busier sections over several lessons.
Practise the acceleration lane repeatedly. Ask your instructor to take several consecutive slip roads so you can practise the joining sequence multiple times in one lesson. Repetition is the fastest way to build confidence at speed.
Use a commentary drive. Narrate your lane choices, your overtaking sequence, and your exit preparation aloud. This surfaces gaps in your understanding more quickly than silent driving.
Count the countdown markers. 300m, 200m, 100m markers precede every exit. Knowing they are coming allows you to prepare rather than react when you spot the slip road appearing at the last moment.
Track Your Progress
Many pupils have their first dual carriageway experience very late in their training, which means they arrive at test standard without having had the chance to build genuine confidence at speed. Ask your instructor to include dual carriageway driving from around 15–20 hours in, even if it feels early. Earlier exposure makes a significant difference to confidence on test day.
Related Skills
- Country Roads (Skill 21) — the rural road skill that immediately precedes dual carriageways in the DVSA framework
- Motorway Driving (Skill 23) — the next step up, with higher-volume traffic and additional motorway-specific rules
- Road Types Skills Overview — see all road type skills in context