Driver location signs

METRICATION:  90% complete
	Metric	Non-metric
	Distance marker posts in kilometres	Junction names don’t use metric distance information
	Driver location signs in kilometres

Distance marker posts

Since at least the 1970s, motorways have had distance marker posts installed at 100 metre intervals at the edge of the hard shoulder. They are also installed alongside many all-purpose trunk roads.

Distance marker posts provide location reference points which are used by road maintenance and emergency services. For drivers that become stranded, they are also marked with an arrow pointing in the direction of the nearest emergency telephone.

The numbers on the post show the motorway or road number, the carriageway (in standard highways parlance of ‘A’ away from London, and ‘B’ towards London, or in the case of the M25, ‘A’ for clockwise and ‘B’ for anticlockwise), and a zero reference point which is the distance from the designated start point of the road in kilometres, to one decimal place.

Driver location signs

By the early 2000s, drivers were increasingly relying on their mobile phones for contacting emergency services on motorways, rather than making use of less convenient roadside emergency telephones.

This meant that the driver location information which was previously relayed automatically by the roadside phones, was now having to be provided by drivers themselves.

The location information on distance marker posts is not always easy for drivers to find, especially at night. Reading the marker posts usually necessitates getting out of the vehicle. The Highways Agency realised that a new approach was needed.

In 2003, newly designed driver location signs were installed on the M25 on an experimental trial basis. Signs were installed at 500-metre intervals. In common with the distance marker posts which they complement, locations were shown in kilometres to one decimal place.

A Highways Agency public information leaflet – 2008

Following the success of the 2003 trial, on 1 March 2007, The Secretary of State for Transport signed the authorisation necessary for the installation of driver location signs on motorway and all-purpose trunk roads throughout England.

By 2010, driver location signs had been installed throughout the English motorway network, and on many A-roads.

Driver location signs first appeared in the TSRGD in the 2016 revision, but have not yet been installed on motorways in Scotland or Wales.

Motorway junction names

Motorway junctions in the UK have historically been named according to the order of their occurrence from the motorway’s start point. Thus the first junction along the ‘A’ carriageway would be named ‘J1’, and the next junction ‘J2’, and so on. This method of naming junctions has three notable shortcomings:

• The junction name provides no inate distance information. It is not possible to know the distance between one junction and the next.
• When new junctions need to be added to an existing road, the number sequence breaks down and supplementary letters are needed, e.g. J10A on the M6.
• Junction numbers create an imprecise secondary location method, that is incompatible with the kilometre-based system used for distance marker posts.

All of these shortcomings can be addressed by the adoption of metric junction names:

• For instances where the letter ‘J’ is currently used, and to make a distinction from the old naming system, new junction names could use the letter ‘K’. This would also serve to indicate that the junction name refers to its kilometre position. The numerical part of the junction name would then simply be the whole number part of the nearest distance marker post’s kilometre reference. The distance in kilometres between one junction and the next could be found simply by subtracting the smallest junction number from the largest.
• When new junctions are needed, they can be named as per the existing junctions, without any need for supplementary letters.
• The same single location reference system can be used for both junction names and distance marker posts.

The adoption of a metric junction naming system brings additional benefits that are not possible with the current naming system:

• Driver location signs will be imparted with an extra use. Their use will no longer be restricted to emergencies. Driver location signs will be useful as countdown markers to a driver’s destination junction.
• As drivers become familiar with the new metric names of the junctions in their locality, they will also be learning the distances in kilometres between these places.

Some examples of motorway junctions using metric junction names

M6			M25
Current name	Metric name		Current name	Metric name
J21	K302		J16	K102
J21A	K306		J17	K110
J22	K309		J18	K112
J23	K314		J19	K116
J24	K316		J20	K118
J25	K318		J21	K122
J26	K322		J21A	K123
J27	K329		J22	K129
J28	K341		J23	K134

In the examples above, using the metric junction names alone, it can be deduced that the distance between junctions K329 and K341 of the M6 is 12 km. The existing junction naming system does not provide this benefit.