The purpose of this web page is to explain the obligations of highway authorities to provide and maintain signs to inform drivers of speed limits, so that drivers are able to check whether they may have a legal defence to a charge of exceeding a limit if those obligations have not been met. The requirements on highway authorities changed significantly on 22 April 2016, which could make it more difficult for drivers who were genuinely confused about the speed limit to obtain justice. The previous information on this website about speed limit signing requirements has thus been superseded, but it has been retained as archive material so that differences between the current and previous requirements can be seen.

The information that follows is not qualified legal advice — if, after reading it, you believe that you have been wrongly accused of exceeding a speed limit, you should seek professional advice from a solicitor with experience of motoring cases.

Legal requirements to install and maintain speed limit signs

The primary legislation which sets out the powers of highway authorities to introduce speed limits, and the requirements on those authorities to erect signs to advise drivers of the limits, is the Road Traffic Regulation Act 1984 (which will be referred to as 'RTRA84' from now on). The legal requirements for the signing of speed limits are set out in section 85 of the Act, and the relevant subsections are as follows:
(1)For the purpose of securing that adequate guidance is given to drivers of motor vehicles as to whether any, and if so what, limit of speed is to be observed on any road, it shall be the duty of the Secretary of State, in the case of a trunk road, to erect and maintain the prescribed traffic signs in such positions as may be requisite for that purpose.
(2)In the case of any road which is not a trunk road, it shall be the duty of the local authority -
 (a)to erect and maintain the prescribed traffic signs in such positions as may be requisite in order to give effect to general or other directions given by the Secretary of State for the purpose mentioned in subsection (1) above, and
(b)to alter or remove traffic signs as may be requisite in order to give effect to such directions, either in consequence of the making of an order by the Secretary of State or otherwise.
(4)Where no system of street lighting furnished by means of lamps placed not more than 200 yards apart is provided on a road, but a limit of speed is to be observed on the road, a person shall not be convicted of driving a motor vehicle on the road at a speed exceeding the limit unless the limit is indicated by means of such traffic signs as are mentioned in subsection (1) or subsection (2) above.
(7)The power to give general directions under subsection (2) above shall be exercisable by statutory instrument.
The statutory instrument referred to in subsection 7 is the Traffic Signs Regulations and General Directions (TSRGD). This document specifies the prescribed traffic signs mentioned in the Act and only signs authorised within TSRGD can be legally placed on a public highway. The regulations and directions within the document specify the circumstances under which highway authorities are allowed (or required) to use these signs.
Amendments and additions are made to TSRGD over time and occasionally a completely new edition is issued. The current version came into effect on 22 April 2016, at which time the previous edition (from 2002) and its subsequent amendments were revoked.
All editions of TSRGD prior to 2016 have been highly prescriptive about where speed limit signs must (or must not) be installed, so that a failure to comply could be cited by a driver as a defence to a charge of exceeding a speed limit. Note that subsections 1 and 2 of section 85 of RTRA84 refer to erecting and maintaining the ‘requisite’ signs to comply with the directions given by the Secretary of State (for Transport). Thus the purpose of TSRGD is to set out those requirements.
The 2016 edition, however, contains very few absolute requirements about the placing of speed limit signs. Instead, it gives highway authorities much greater flexibility about whether and where signs are used. A situation could develop over time, therefore, where speed limit signing becomes less clear and may vary significantly between different highway authority areas. This would increase the risk of drivers becoming confused and exceeding speed limits inadvertently. Any prosecutions arising would be more difficult to defend because TSRGD is so vague about what is ‘requisite’.
(The changes to TSRGD in the 2016 edition do not just apply to speed limit signing but also give flexibility to signing other types of traffic regulations, such as waiting restrictions. This webpage, however, is concerned only with speed limit signs.)

Speed limit signs

Every sign approved for use on the public highway in TSRGD is allocated a diagram number. The two signs most commonly used to indicate a maximum speed limit are diagrams and 671, as follows:
Diagram 670
Diagram 671
Diagram 670 can indicate any speed limit from 20 to 70mph (usually in multiples of 10mph) and the signs can be from 300mm to 1500mm in diameter. Diagram 671, sometimes known as the 'derestriction' sign, has the international meaning 'end of maximum speed limit'. In the UK, however, it has been given the meaning 'national speed limit applies', which means a 60mph speed limit on single carriageway roads and a 70mph speed limit on dual carriageway roads and motorways.
With the introduction in recent years of 20mph speed limit zones, diagrams 674 and 675 may be encountered, at the beginning and end of such a zone, as follows:
Diagram 674
Diagram 675

The bottom part of diagram 674 can show a road safety slogan instead of a place name or it may be omitted altogether. The top part of diagram 675 can show any speed limit from 20 to 70mph or it can show the 'derestriction' sign (diagram 671), as appropriate.
Very rarely, a minimum speed limit may be encountered. The signs to indicate the start and end of a minimum speed limit are diagrams 672 and 673, respectively:
Diagram 672
Diagram 673

Placing of speed limit signs

In previous editions of TSRGD, there were strict rules on where speed limit signs had to be placed. These rules included: Full details of the previous requirements can be seen in the archive material.
Direction 8 of TSRGD sets out the requirements for the placing of signs to indicate the beginning of a restriction, requirement, prohibition or speed limit. The first paragraph of direction 8 lists the diagram numbers of the signs to which the direction applies, including diagrams 670 and 674 (See above). The other paragraphs relevant to speed limits are as follows:

The new rules on placing speed limit signs

In the 2016 version of TSRGD, the rules governing the use of speed limit signs are set out in Schedule 10. The important points are as follows:  

Implications of the new rules

The new regulations and directions place no legal obligation on highway authorities to provide terminal or repeater signs at all. If terminal signs are provided, they have to meet some simple requirements, but nothing else.
It would clearly not be possible to enforce a speed limit if there were no signs whatsoever to inform drivers of it. In the absence of specific requirements, however, a driver prosecuted for speeding would have to take the financial risk of going to court to try to show that the signing was inadequate and he or she was genuinely unaware of the limit. Many people would be deterred by the prospect and would accept a fine or speed awareness course instead.
Particular situations where drivers could easily fall foul of an unknown speed limit are described below.
Street lighting defining a speed limit
Sections 81 and 82 of RTRA84 make it a criminal offence to exceed 30mph in a motor vehicle on a ‘restricted road’. A restricted road is defined as one where there is “a system of street lighting furnished by means of lamps placed not more than 200 yards (183 metres) apart”. (The meaning of ‘street lighting’ can create uncertainty about whether certain lighting systems comply with this definition and this will be discussed below.)
Drivers are expected to know that a system of street lighting means that a road carries a 30mph speed limit, unless signs show otherwise. So, when entering a built-up area from an unlit rural road, the start of the lighting system should be taken to mean the start of a 30mph limit in the absence of signs to the contrary. Under the new TSRGD, no terminal signs are required. However, it is not unusual for a higher speed limit, e.g. 40mph, to apply along lit, suburban sections of road before a 30mph limit comes into force closer to a town centre. In such a case, ways in which the relaxed requirements could confuse drivers are: On rural roads that are generally unlit, highway authorities will sometimes introduce street lighting for short lengths in the vicinity of junctions or other hazardous locations to improve safety at night. In most cases, the authority will have taken the legal steps necessary to remove the restricted road status that would otherwise have applied automatically. Under the old TSRGD, it was a requirement in such cases for diagram 671 (‘derestriction’) signs to be displayed to indicate to drivers that a 30mph speed limit does not apply.
It was not unusual for some highway authorities to fail to comply with this requirement and its absence in the new regulations will doubtless mean that more such locations will not be signed. This could again lead to confusion between regular and occasional users of a road about whether a 30mph limit or the national limit applies. Cautious drivers might slow down to 30mph while others would continue at 60mph (or 70mph on a dual carriageway). Large differences in speed between vehicles contribute significantly to road accidents, so confusion in these locations would be detrimental to road safety.
If a driver were prosecuted for exceeding 30mph on an unsigned length of lit rural road, they would need to check with the highway authority whether restricted road status had been removed. Depending on how long ago the street lighting was introduced and the quality of record keeping by the authority, this might be difficult or impossible to ascertain, leading to possible miscarriages of justice.
(It should be noted that RTRA84 excludes motorways from becoming restricted roads, so the presence of street lighting on a motorway does not create a 30mph speed limit.)
The definition of street lighting
It was stated above that the RTRA84 definition of a restricted road means one where there is a system of ‘street’ lighting with lamps not more than 200 yards (183 metres) apart. However, the ban on 30mph repeater signs on lit roads in both the old and new TSRGD applies to roads with a 30mph limit and a system of ‘carriageway’ lighting.
To understand the difference it is necessary to refer to the Highways Act 1980 (HA80). The carriageway is that part of the highway intended for the use of vehicles, as defined in section 329, so a system of carriageway lighting must be designed to illuminate the roadway itself and not just the footways. HA80, section 270, defines a ‘footway lighting system’ and a ‘road lighting system’ as follows:
"footway lighting system" means a system of lighting, provided for a highway, which satisfies the following conditions, namely, that either —
(a)no lamp is mounted more than 13 feet above ground level, or
(b)no lamp is mounted more than 20 feet above ground level and there is at least one interval of more than 50 yards between adjacent lamps in the system;
"road lighting system" means a lighting system that is not a footway lighting system.
Subparagraph (a) makes it clear that, where street lamps are less than 13 feet (3.96 metres) high, they constitute a footway lighting system, not a road lighting system, regardless of their spacing. (In this context, ‘road’ is synonymous with ‘street’ or ‘highway’, in meaning any part of the carriageway, footways and verges. Thus a carriageway lighting system would constitute a road or street lighting system, but a footway lighting system would not.)
Subparagraph (b) says that, where street lamps are between 13 feet (3.96 metres) and 20 feet (6.1 metres) high, they constitute a road lighting system only if there are no gaps greater than 50 yards (45.7 metres) between any pair of lamps in the system. Thus only street lamps higher than 20 feet (6.1 metres) automatically qualify as a street lighting system within the definition of a restricted road in RTRA84, provided they are no more than 200 yards (183 metres) apart.
In practice, lamps more than 20 feet (6.1.metres) high are normally only installed on roads used by significant amounts of through traffic. In residential areas, it is more normal for lamps to be between 13 feet (3.96 metres) and 20 feet (6.1 metres) high and spaced no more than 50 yards (45.7 metres) apart.
If any system of lighting does not comply with the height and spacing requirements to make it a ‘road lighting system’, then the road is not automatically a restricted road. RTRA84 does make provision for roads to be legally made into restricted roads that do not meet the basic definition, but in such a case the highway authority would need to make a traffic regulation order to that effect. In the absence of such an order (or the absence of a speed limit order other than 30mph), the road would be subject to the national speed limit.
Also, if a system of lighting only meets the definition of footway lighting, not carriageway lighting, but the road carries a 30mph speed limit by virtue of a traffic regulation order, then the ban on 30mph repeater signs does not apply.
Street lighting not illuminated at night
Repeater speed limit signs on street-lit roads with a 30mph limit are not permitted as the street lights themselves effectively set the speed limit. In recent years, highway authorities in pursuit of cost savings have been turning off some street lighting, either completely or for just part of the night. This has implications about the enforceability of 30mph speed limits where street lights are not illuminated during the hours of darkness.
There is case law in which prosecutions for exceeding a 30mph limit were dismissed because lighting systems had failed. Consequently, there may be a viable defence to a charge of exceeding a 30mph limit where street lighting had been deliberately turned off at night.


The implications of the new regulations as shown above may seem complex, which indeed they are. It must be stressed that these are the ABD's interpretation of the new regulations in the context of the primary legislation (Acts of Parliament). It is ultimately a court of law that interprets the legislation in individual cases, which is why it is essential for anyone wanting to challenge a speeding prosecution on the basis of inadequate signage to obtain legal advice from a solicitor specialising in motoring cases.

Government advice to highway authorities

In May 2016 the Department for Transport issued Circular 01/2016, which contains guidance to highway authorities on how to interpret TSRGD 2016. In the section on speed limit signs, it claims that the requirements regarding the provision of terminal signs at the start and end of a speed limit have merely been ‘relaxed’ and that at least one terminal sign is still required. It warns that any decision to reduce the number of terminal signs should be underpinned ‘by robust risk analysis’.
The circular further recommends that the siting of speed limit signs should have regard to guidance in Chapter 3 of the Traffic Signs Manual. This document is also a Department for Transport publication and its current edition dates from 2008. Its recommendations, therefore, are based on the requirements of the now superseded TSRGD 2002 and are similar to the interpretation of the 2002 regulations in the ABD's archive material. In addition to the positioning of terminal speed limit signs, Chapter 3 contains recommendations on their diameter and the distances from which they should be visible, according to the speed limit in force. It also contains recommendations on the spacing of repeater signs.
It is important to stress that Circular 01/2016 and Chapter 3 contain only guidance and do not have the force of law. While their recommendations could be cited as good practice by the defence if a speeding case goes to court, the prosecution could argue that failure to comply does not invalidate a speeding charge as no statutory requirement has been breached. The primary legislation (RTRA84) and secondary legislation (TSRGD 2016) contain no absolute requirements to provide terminal or repeater speed limit signs at all, contrary to the claim in Circular 01/2016.
If the intention of TSRGD 2016 was that at least one terminal sign should be placed at the start of any speed limit, as the Department for Transport claims, then it would have been a simple matter for an additional direction to have been included that might be worded:
“At the start of any speed limit, a minimum of one terminal sign must be provided.”
This would be straightforward and unambiguous, which begs the question as to why such a clarification of the legal requirement was not included. Readers will no doubt draw their own conclusions.