Slip Roads

What are they?

Slip roads are roads intended to help you increase or decrease your speed when joining or leaving a carriageway, or more often a motorway.

When you realise that on a motorway, vehicles will be travelling around 70MPH, you want to be pretty close to this speed when merging with the traffic so that you don’t become a hazard to traffic already on the carriageway.

You could call a slip road "A Change Speed Lane", because most of the time it is a stretch of road intended to be used to either accelerate up to an appropriate speed, or decelerate up to a junction, there are occasions when a slip road will turn into it's own road.

Speed limits to be aware of when changing roads

You can find slip roads all over the UK, there are some things to think about when joining a slip road, like will the slip road merge onto the carriageway or become a lane itself?, The speed limit on the carriageway and whether or not it is safe for you to join. You should start by knowing the speed limit on the carriageway, this will be shown on a signpost on the slip road so that you are aware of the speed that traffic is already travelling at.

Next you need to see how the slip road will merge onto the carriageway,

have a look at the figures below:

Figure 1

Figure 1: The left lane of slip road becomes a lane itself, and the right lane merges with traffic.

Figure 2. The right lane of slip road becomes a lane itself, whilst the left lane of slip road merges with traffic.

Figure 2

Figures 1 and 2 will be seen when using a slip road to join a motorway, when looking at figure 1 you can see that the slip road comprises of 2 lanes,

with the left of the two lanes becoming a lane itself on the motorway and therefore you won’t have to worry about joining,

(but you should still check your right mirror when joining).

If you use the right of the two slip road lanes then you will have to give priority to traffic already on the motorway.

Figure 3

Figure 3 is a reverse of this situation, where the left lane of the slip road has to give way to the right lane of the slip road, you should always look at slip road signs as this will prevent any confusion when the slip road comes to an end.

Check out the typical slip road sign for a dual carriageway shown in the above picture, notice the difference of angle of the road you are on in the sign on the carriageway, and on the slip road as it merges, this denotes the road you are on as straight up.

Notice the sign informing you that you will be joining traffic and the relatively short amount of space you have to join the traffic already on the carriageway.

This type of slip road warning sign is typical on a dual carriageway (rather than a motorway), you should make sure you don’t go over the hatched markings to join traffic.

Slip roads come in all shapes and sizes so use your initiative, don’t completely focus on your right mirror to see if you can join because you might run out of slip road and collide with the kerb.

Its worth checking your right shoulder briefly before joining to make sure there isn’t a vehicle in your blind spot, and if its appropriate you should try to get as close to the speed of the traffic already on the carriageway so you can filter in comfortably without becoming a hazard.

With careful planning you should never have to stop on a slip road unless there is heavy congestion already on the carriageway.

Also, never assume someone will give you way when you join.