Dual Carriageways

Dual Carriageways

Dual carriageways require a slightly different approach compared to normal, city driving. When driving normally, we learn to accelerate and brake gently. It is important to recognise that to use dual carriageways safely, the ability to accelerate and decelerate rapidly is required. This means using more gas when joining the dual carriageway, and leaving gear changes slightly later in order to take advance of the greater acceleration offered by lower gears. This is especially so if travelling up hill while accelerating. Don't be afraid to make some noise with the engine, and make full use of the lower gears to fight against gravity and get the speed up!

Once on the dual carriageway you will normally be travelling at higher speeds, up to 70 MPH. This can seem very fast at first, but you will quickly adjust to the higher speed and before long it will start to feel normal. There are a lot less hazards on dual carriageways compared to most other roads: no cyclists, no pedestrians, no parked cars, no bus stops etc. This makes it possible to travel at higher speeds while still planning ahead and staying safe. Once you exit the dual carriageway, however, there is a very important transformation that must take place: you must mentally adjust to the lower speeds that are required. 

When you leave a dual carriageway, your perception of speed can be heavily distorted. 30 or 40 MPH can feel very slow once you have adjusted to driving a higher speed. It is essential to recognise that, in many situations, 30 MPH is much too fast. For example, after leaving the dual carriageway you could find yourself approaching a junction such as a roundabout or a give way. Normally you would bring your speed down below 20 MPH on approach to one of these junctions, sometimes below 10 or even 5 MPH. Having just left a dual carriageway, however, 30 MPH can feel like a sensible speed to approach. Make use of your speedometer to inform you of your actual speed in these situations. Don't trust your instincts as they are likely to mislead you. 

Similarly, coming into a built-up area after leaving a dual carriageway requires a significant shift in your perceptions to ensure you are travelling at a safe and sensible speed, with enough time to plan ahead and prepare well for all potential hazards.

Slip Road - On

The slip road provides space for you to accelerate up to a speed that roughly matches the other vehicles already on the dual carriageway.

Look for the speed limit sign on the slip road. Although speed limits should not generally be thought of as targets, in this situation the speed limit can provide a good indication of the speed that other vehicles are likely to be travelling. So you can merge safely with the other vehicles, it makes sense to use the slip road to get close to this speed if possible. This means you will be accelerating more rapidly than you are used to in normal driving.

As always, you should know what is going on behind you before accelerating.
Joining dual carriageway from slip road

Position 


Some slip roads are divided into lanes, in which case the usual rules regarding lane discipline should be applied. 


Many slip roads consist of a single, wide lane. In this case, it is normal to proceed in the middle of the available space. If you need to overtake someone on the slip road, this should always be done on the right. Similarly, if another road user wishes to overtake you, move to the left and allow space for them to pass on the right.

 


Signal

Signal right to indicate your intention to join the main carriageway. This should be done nice and early to attract the attention of traffic already on the dual carriageway. By getting yourself noticed early, you will make it easier for everyone to facilitate a safe merge. This is especially true at night, when it can be very difficult to tell if another vehicle ahead is joining from a slip road or already on the main carriageway. An early signal makes all the difference in this situation.


Observations


As you get close to the main carriageway, you should already have your speed well up and your right signal on.


Use your right mirror to get an idea of how much space is available for you to merge into. If there appears to be plenty of space, all you need to do is have a quick glance into your right blindspot and, if definitely clear, ease into the left lane of the main carriageway.


If there are many other road users on the dual carriageway, you should find that they will do whatever is necessary to enable you to join. This may mean moving over to the right lane (look out for anyone giving a right signal), or they may simply adjust their speed a little to create space for you. It is at this point that you will be glad you got your speed up nice and early on the slip road. If you are travelling too slowly at this point, it can be difficult to get your speed up quickly enough to keep up with the other vehicles you are trying to merge with. If, however, the other vehicles are travelling more slowly than you are, it is a simple matter to adjust your speed down a little. Once your speed is matched to the other vehicles, you should find it is fairly straightforward to identify a gap and move into it.


Try to get as much information as possible using your mirrors, especially your right mirror. While it is important to check your right blindspot before committing yourself onto the main carriageway, it is also very important that you have your eyes on the road in front of you as much as possible, especially when travelling at higher speeds.


Only in vary rare circumstances, when the dual carriageway is very busy, might you find yourself unable to merge from the slip road without stopping and waiting for a gap.

 

On the dual carriageway

Once you have joined the dual carriageway, it is important to cancel your signal straight away so it does not mislead others into thinking you are about to change lanes. Focus on staying in the centre of your lane. As always, keep an eye on your mirrors so you know what is happening behind you, and try to maintain a safe, sensible speed for the conditions. Use the “two second rule” to keep a safe gap in front of you and ensure that you can stop safely at any time. If another road user gets too close behind you, increase the space in front of you so you have even more reaction time available. Remember to at least double stopping distances for wet weather, and increase them even more for icy or foggy conditions.

Slip Road - Off

Just as slip roads provide room to accelerate before joining the dual carriageway, they also provide space to decelerate after leaving. Use the slip road for this purpose; if possible, avoid slowing down before entering the slip road. Keeping your speed up will enable other road users behind you on the dual carriageway to maintain their speed while you prepare to exit.


When planning to exit, make sure you are in the left lane nice and early, preferably at least half a mile before the slip road begins. Look out for the signs which count down the distance to the slip road. Each diagonal line on the countdown signs represents one hundred yards, so the first sign indicates a distance of three hundred yards to the exit.


Check your mirrors and signal left as the countdown begins. Remember to maintain your speed while still on the dual carriageway.

 


Exiting

Cross the broken white line to move onto the slip road.


Once your vehicle has entered the slip road, cancel your signal and begin to slow down if it is safe to do so.


As always, use your mirrors to make sure you know what is going on behind you before slowing down.

 


On the slip road

Bring your speed down steadily, looking ahead to see how much space you have available.


Look either side of the slip road for signs. You may see signs warning you of a junction or other hazard ahead. You should see signs indicating a change of speed limit. Use this information to plan ahead, making sure you achieve an appropriate speed for whatever you are going to deal with next.


Remember, you are likely to be cutting your speed dramatically in this situation. This rapid change in speed can be deceiving, so make sure you look at your speedometer to check that you are slowing down sufficiently for the situation. Forty miles per hour can feel very slow indeed when you have just left a dual carriageway, but if you are approaching a junction then you almost certainly have a good deal more braking still to do.


As you decelerate, use the MSPSL routine to safely select the correct signal, position and speed for whatever is coming next. As usual, aim to take position on the left unless you have a sensible reason for doing otherwise.

 
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