Knowing your speed limits

The Highway Code states that 'you must not exceed the maximum speed limits for the road and for your vehicle'.

What speed it is safe to drive at is a continuous decision making process. And to that extent, is a more difficult judgement to make. Drivers rightly consider poor lane discipline, failure to signal, driving too close and other errors to be poor driving. There is some reluctance to accept that driving too fast is also poor driving, but it is and there is a need to alter that thinking.

The diagram below shows the speed limits that are applicable to your vehicle. You can also view this table by clicking on the following link Highway Code - speed limits table

Who has responsibility for speed limits?

A central body called the Highways Agency sets speed limits on the motorway and trunk road network. The Government provides advice (Department for Transport) to traffic authorities (County, District and Borough Councils, but not Parish Councils) on the setting of local speed limits.

It is for those authorities to decide what the most appropriate speed limits for their roads are, based upon local considerations and circumstances. This would usually reflect factors such as accident history, traffic flows, road traffic mix, levels of adjacent development and road geometry. They can set speed limits from 20mph to 70mph inclusive.

Speed limits at road works

These are often lowered at road works. There are valid reasons for doing this. The safety of those dedicated to repairing our road network is paramount and therefore vehicle speeds will need to be lowered where workmen are likely to be present.

In addition, the carriageway will be narrowed to allow work to progress. Such narrowing will inevitably mean it is appropriate to reduce vehicle speeds. Lower speed limits will help to achieve this.

Dual carriageways

There is sometimes some confusion as to what a dual carriageway is, especially for those vehicles restricted to speed limits below that for cars, such as HGVs and coaches.
In short, a dual carriageway is a road that is separated by a central reservation. A central reservation is anything other than a pedestrian refuge that separates vehicles going in one direction from vehicles going in the other direction.
It should be noted that, although it is more usual to have two or more lanes in each direction, the number of lanes is not specified, i.e. it is the presence of a central reservation rather than the number of lanes that determines whether or not a road is a dual carriageway.

Different speed limits and how to recognise them

20mph speed limit

The 20mph speed limit is predominately used in urban areas.
Commonly you will see them in town centres, high streets, residential roads and in the vicinity of schools. The aim of this limit is to reduce vehicle speeds that allows for the presence of vulnerable road users such as cyclists, children and the elderly.
More often than not a 20mph speed limit will come in the form of a ‘zone’. A zone will contain traffic calming features, usually road humps that force drivers to reduce their speed to around 20mph.
Research on the effectiveness of these zones has shown that casualties can fall by up to 70% where they have been introduced.

30mph speed limit

This speed limit is predominately used in urban areas (and more recently in many villages) and is usually indicated by the presence of a system of street lights.
The existence of street lights is the way we recognise this speed limit and it is the reason why you do not see, apart from where the limit starts, 30mph repeater speed limit signs.
Some believe this to be an odd way of indicating a speed limit, but really it is simple. If there are street lights and no signs to the contrary, a 30mph speed limit is in force.
There are a number of unlit roads where a 30mph speed limit applies. In these circumstances the traffic authority must place 30mph repeater signs.

40mph and 50mph speed limits

These two speed limits were introduced in the 1970s and are predominately used in non-built up areas or in built up areas where a higher speed is both safe and appropriate.
In addition to signing the beginning of the speed limit, traffic authorities must also place speed limit repeater signs at regular intervals along the length of road being enforced. The driver should therefore be in no doubt of what the speed limit is for the road being driven on.

National speed limit

This is indicated by a round sign showing a white background with a diagonal black stripe across it.
For the majority of vehicles it means 60mph on single carriageway roads and 70mph on dual carriageway roads (as detailed above, some vehicles are restricted to lower speed limits).
This speed limit works on the same principle as the 30mph speed limit in that it is not signed apart from where the speed limit starts. It is predominately used along the rural road network.
Again, recognising it is simple. Where there are no street lights and no signs to the contrary, the national speed limit is in force.
The speed limit on a motorway is 70mph unless otherwise indicated.

Department for Transport

More information on road safety can be found by clicking on the link below:

Department for Transport - Road Safety