Motorways vs. Dual Carriageways—What’s the Difference
At Oxon Driving Tuitions, one of the questions we often get from learners is: “What’s the difference between a motorway and a dual carriageway?” Many assume it’s simply the number of lanes—motorways have three or more, and dual carriageways have two. However, the reality is a bit more complex, and understanding these differences can help you become a safer and more informed driver.
Understanding Dual Carriageways
The term dual carriageway is often misunderstood. While “dual” does mean two, it doesn’t refer to the number of lanes but rather the number of carriageways—the separated sections of road for opposing directions of traffic. A central reservation (which could be a barrier, grass verge, or kerb) divides these two carriageways. Each can have one lane or multiple lanes, but the presence of two physically separated carriageways is what defines it as a dual carriageway.
What Is a Motorway Then?
A motorway is a type of road that has been specifically built to motorway standards. This status is defined not by the number of lanes it has, but by its design and the rules that apply to it.
In fact, not all motorways are dual carriageways! For example, the A38(M) in Birmingham operates with a tidal flow system and is still classified as a motorway despite not having separate carriageways in the usual sense.
Design and Safety Differences
Here are some key differences between motorways and A-roads, even when both have a 70 mph speed limit:
Slip Roads: Motorways typically have longer, better-designed slip roads to allow drivers to build up speed safely before merging. A-roads may have shorter slip roads or even junctions with traffic lights.
Hard Shoulders: Motorways include a hard shoulder for emergency stops—something A-roads don’t always have. Some modern motorways, however, now use the hard shoulder as a live lane during peak times.
Lay-bys and Parking: You’ll often find lay-bys on A-roads, but not on motorways. On motorways, stopping is only permitted in emergencies, usually in designated emergency refuge areas.
Fewer Junctions: Motorways have fewer entry and exit points compared to A-roads, which reduces the chance of collisions and helps maintain a smooth flow of traffic.
Signage: Blue signs indicate a motorway. In contrast, green signs are used on A-roads. Motorway signs also give more advanced warning for upcoming junctions and directions.
Rules and Restrictions
There are strict rules about who can use a motorway. According to Rule 253 of the Highway Code, the following are not allowed on motorways:
- Pedestrians
- Cyclists
- Motorcycles under 50cc
- Holders of provisional motorcycle licences
- Agricultural vehicles
- Certain slow-moving or oversized vehicles
- Mobility scooters and powered wheelchairs
Previously, learners were also not allowed on motorways. Fortunately, that has changed. Now, learner drivers can drive on the motorway as long as they are accompanied by an approved driving instructor in a dual-controlled car. This is a great opportunity for learners to gain valuable experience in a safer, more forgiving environment, especially when learning how to use slip roads.
However, if you’re being supervised by a family member or friend (on a provisional license), motorway driving is still not permitted.
Speed Limits for Different Vehicles
Speed limits aren’t the same for every vehicle. For example:
- Motorhomes over 3.05 tonnes:
- 60 mph on a dual carriageway
- 70 mph on a motorway
- Goods vehicles over 7.5 tonnes (England & Wales):
- 60 mph on both motorways and dual carriageways
- Goods vehicles over 7.5 tonnes (Scotland):
- 50 mph on dual carriageways
- 60 mph on motorways
So it’s not just the type of road that matters, but also what vehicle you’re driving and where in the UK you’re driving it.
Who Can Use the Right Lane on a Motorway?
According to Rule 265 of the Highway Code, not everyone is allowed to use the right-hand lane (the “fast lane”) of a motorway. For example:
- Vehicles towing trailers
- Goods vehicles over 7.5 tonnes
These must stay in the left or middle lanes and must not use the far right lane unless directed to do so by traffic signs.
How to Identify a Motorway
While most motorway names begin with an “M” (like M40 or M25), some are part of A-roads but have motorway status, such as the A1(M). The easiest way to know you’re on a motorway is by looking at the directional signs—motorway signs are always blue.
In Summary
Understanding the difference between motorways and dual carriageways is more than a matter of counting lanes. It’s about knowing the road’s layout, its rules, and who can legally use it. As a learner, becoming familiar with both types of roads—under the guidance of a qualified instructor—can give you greater confidence and a broader skillset as a new driver.