How do we identify a dual carriageway?

 

Despite contain the word “dual”, a dual carriageway can have 1, 2, 3 or even 4 lanes on each side!

 

Likewise, a single carriageway can have more than one lane!

 

Confused yet?

 

It’s best to classify roads not by the number of lanes, but by their appearance.

 

A single carriageway is one piece of road containing traffic travelling in both directions with no physical barrier dividing each side.

 

A dual carriageway is two separate pieces of road divided by some kind of central division that separates the traffic travelling in opposite directions. The central division can be a metal barrier, grass verge, pavement, bushes etc.

For now, we’ll look at how we use dual carridgeways, later in this course we learn more about road identification and how to apply the National Speed Limit.

Let’s look at the three areas will need to learn to use dual carriageways.

           

Joining - General driving - Exiting

 

Joining a dual carriageway 

There are three main ways we’d expect to join a dual carriage way.

• From an entry slip road
• When a single carriageway or Motorway merges into a dual carriageway
• Emerging from a minor road onto a dual carriageway

 

Entry slip roads

An entry slip road will often come from some type of junction.

 

It’s a joining lane to give us a chance to meet the pace of the established traffic before joining the dual carriageway.

 

We can use our MSPSL routine to join safely

 

Mirror

We check our interior and right mirror

 

Signal

We signal our intentions to join, note that we are not signalling to say we are moving over straight away, we are just letting the established traffic know we are looking to join. If they see us signalling, they may help facilitate our join by moving over or changing speed to help out.

 

Position

We move just to the left of lane one, making sure not to cross the slip lane give way line.

 

Speed

We adjust our speed to meet a gap in the traffic.

 

Look

We check our right mirror and blind spot for a suitable gap before moving onto the carriageway. We need to be 100% sure we are not pulling over into another vehicle.

 

When we are on the carriageway, we check our interior mirror before changing speed.

 

When joining, we want to fit into a gap and not move into anyone’s safety margin (a safety margin is the distance in front of a moving car that it needs to come to a safe stop, we’ll go into more detail about safety margins later in the course).

 

If we need to squeeze into a gap and compromise our safety margin, we must reclaim this safety margin as soon as possible.

 

In most cases, you will join with no problems, you’ll adjust your speed to the pace of the traffic, cars might even move over or slow down to help you join.

 

Remember, the established traffic has right of way, we must not cross the give way line at the end of the slip road if it may cause another vehicle to slow down or change lanes unexpectedly.

 

 

If you can’t find a gap, stop at the give way line and wait for a suitable gap, you will need to consider accelerating faster to meet the pace of the traffic.

 

Dual carriageway ahead

Another way we can join a dual carriageway is when the road merges from a single carriageway or Motorway.

 

We’d expect some signs to warn us of this road change ahead including.

 

            “Dual Carriageway ahead”

            “Keep Left”

            “National speed limit sign”

 

As we join the dual carriageway, we will keep to the left as the lanes divide into two unless we want to pass slower traffic.

 

If increasing speed, we should check our interior mirror before speeding up

 

Joining from a minor road

If a minor road (side road) meets a dual carriageway, we must observe any signs on approach. We would likely see a blue “dual carriageway ahead” sign and maybe a “no right turn sign” if there is no gap in the central barrier allowing a right turn.

 

This diagram shows a central reservation with a gap in, so we can turn left or right (We are the yellow car).

 

When we turn left we need to make sure we find a suitable gap before pulling out. When turning right, we need to make sure when crossing oncoming traffic, we can also join the other side of the dual carriageway in one movement, unless there is a safe spot in the central reservation to sit and wait.

 

This also applies if going straight ahead by crossing the carriageway.

Driving on a dual carriageway 

Like any road, we need to observe the speed limit and drive at a safe speed.

 

The national speed limit on a dual carriageway for cars is 70mph (unless indicated otherwise)

 

We must also maintain a safe distance from any vehicles in front of us. To measure our breaking distance, we can use the 2 second rule. We’ll look at this in more detail later in the course.

 

If there is more than one lane, we should use the left lane for normal driving.

 

Our position in the lane should be central, between the lane markings (as opposed to 1 meter from the kerb)

 

If we need to overtake slower traffic, we should pass using using a lane to the right.

 

We should not pass slower traffic using the left lane (undertaking) unless traffic in the right lane is signalling right to exit the dual carriageway by making a right turn.

 

We can also pass slower traffic on the left with caution, if the natural flow and pace of the traffic means the left lane is moving faster than the right. This often happens when there is a traffic jam ahead.

 

When we overtake, we can use the MSPSL routine.

 

If we are travelling on a dual carriageway and see traffic ahead slowing down suddenly, we should switch on our hazard lights to warn others behind.

 

If we breakdown on a dual carriageway, we must try to move over to the left lane or hard shoulder to stop, we must switch on the hazard lights and place a hazard triangle 45 metres behind our car.

 

You and any passengers should exit the car and move to a safe place off of the road to the left.

Exiting a dual carriageway

As there are three ways to join a dual carriageway, there are three ways to exit.

 

Exit slip roads

Sometimes referred to as “deceleration lanes”. They give us the chance to wind down our speed before meeting the junction.

 

We should look to move into the left lane at least half a mile before our exit, sooner if the traffic is heavy.

 

We can lookout for the green III, II & I countdown markers.

 

300 yards, 200 yards & 100 yards (100 yards is about 90meters)

 

We can move into the exit slip using our MSPSL routine and enter the slip lane at the earliest opportunity. 

 

We should not apply our brakes to slow down until we have crossed the threshold line of the exit slip road.

           

End of Dual Carriageway

A two lane dual carriageway can end by merging into a one lane single carriageway. (sometimes a dual carriageway can expand into a Motorway "Motorway Ahead")

 

We’d expect to see some signs:

 

“Merge in turn”

“End of dual carriageway” red triangle

Arrows painted on the ground.

 

When we merge in turn, we need to check the wing mirror in the direction of the merging traffic.

 

We should observe the new speed limit when exiting the dual carriageway.

 

Exiting into a minor road

Depending on if there is a right tun lane or gap in the central reservation, we may only be able to exit a dual carriageway to the to the left.

 

We should give plenty of warning to traffic behind with an early signal as we will need to reduce our speed considerably if the exit has a sharp bend.

 

If we can exit to the right, we must ensure we have a sufficient gap when crossing oncoming traffic and appreciate the potential high speeds of that traffic, making it more difficult to judge a suitable gap.

 

In both cases, we can use MSPSL to exit the dual carriageway