This document is published by National Highways.

This document supersedes TA 12/07, TA 16/07, TA 56/87, TA 82/99, TA 84/06, TD 07/07, TD 24/97, TD 35/06, which are withdrawn.

This document forms part of the works specification. It does not purport to include all the necessary provisions of a contract. Users are responsible for applying all appropriate documents applicable to their contract.

This document contains design requirements for traffic signalling installations.

The assumptions made in GG 101 [Ref 3.N] apply to this document.

It is assumed that the parties reading TD 101 are aware of additional documents to those within the DMRB; The Department for Transport (DfT) prepares general advice, some of which is applicable to motorway and all purpose trunk roads. Of these documents, the most relevant are Local Transport Notes (LTN), and Traffic Advisory Leaflets (TAL), which mostly cover topics that apply to local rather than strategic roads, but some are of general relevance.

It is assumed that a traffic signalling engineer will be part of the review process throughout all stages of traffic signalling design.

Where there is a requirement in this document for compliance with any part of a "British Standard" or other technical specification, that requirement may be met by compliance with the Mutual Recognition clause in GG 101 [Ref 3.N].

1.1 This document outlines traffic signalling installation design requirements that shall be implemented on all new or modified traffic signalling installations.

1.2 This document shall be implemented forthwith on all schemes involving traffic signalling installations on the Overseeing Organisations’ motorway and all-purpose trunk roads according to the implementation requirements of GG 101 [Ref 3.N].

1.3 The requirements contained in GG 101 [Ref 3.N] shall be followed in respect of activities covered by this document.

2.1 All electrical work must comply with The Electricity at Work Regulations 1989 UKSI 1989/635 [Ref 7.N].

2.2 All electrical work on traffic signalling systems shall comply with the Requirements for Electrical Installations. IET Wiring Regulations, BS 7671 [Ref 5.N].

2.3 Security threats to traffic signalling systems must be mitigated in accordance with the requirements of The Network and Information Systems Regulations UKSI 2018/506 [Ref 8.N].

2.4 Where evident, security threats to traffic signalling systems shall be assessed, documented, mitigated and managed.

NOTE Examples of security threats to traffic signalling systems can include compromised roadside equipment, in-station equipment, and system software.

2.5 Risk to the existing communications infrastructure by the introduction of new traffic signalling equipment shall be avoided.

2.6 A metal theft risk assessment shall be undertaken at the design stage.

2.6.1 Where a metal theft risk assessment highlights a risk, corresponding measures should be put in place to provide protection to the infrastructure against the risk of theft or damage.

2.7 The design of the traffic signalling installation must meet the requirements of the TSRGD UKSI 2016/362 (TSRGD) [Ref 9.N].

2.8 The design of the traffic signalling installation shall meet the requirements of the Traffic Signs Manual Chapter 6 TSM Chapter 6 2019 [Ref 12.N].

3.1 The applicable provisions of the Construction (Design and Management) Regulations 2015 UKSI 2015/51 [Ref 6.N] must be complied with throughout the life-cycle of the scheme.

3.2 In order to identify and confirm the expected outcomes of the traffic signals installation(s), a consultation shall be arranged with the Overseeing Organisation.

3.2.1 As part of the consultation, the overall objectives and benefits from carrying out the traffic signalling installation should be defined.

NOTE Example objectives and benefits of a traffic signalling installation can include improved journey time reduction, customer experience, safety benefits, and accessibility.

3.3 The extent of the brief for the traffic signalling installation(s) to be undertaken shall be approved with the Overseeing Organisation and recorded.

3.4 A design file for the traffic signalling installation shall be held by the Overseeing Organisation.

NOTE The responsibilities for ownership of the design file are in line with Construction, Design and Management (CDM) regulations UKSI 2015/51 [Ref 6.N], or in Northern Ireland The Construction (Design and Management) Regulations (Northern Ireland) NISR 2016/146 [Ref 2.N] throughout the life-cycle of the scheme.

3.4.1 All aspects associated with the design and implementation process of traffic signalling installations should be agreed with the Overseeing Organisation.

NOTE Agreeing the extent of the brief with the Overseeing Organisation ensures effective planning.

3.5 Consultation with the adjacent authorities to the traffic signalling installation(s) shall be carried out.

3.5.1 The consultation with the adjacent authorities to the traffic signalling installation should agree on the following points:

NOTE Consultation with the adjacent authorities to the traffic signalling installation can help to achieve design and installation acceptance.

3.6 Site conditions shall be assessed prior to commencement of traffic signalling installation design and recorded in the design file.

3.6.1 Site conditions may be assessed by desktop study (reviewing previous reports), video surveys, site visit, ecological surveys, interview surveys, walking, cycling & horse-riding assessment and review, traffic counts and speed surveys.

3.6.2 An assessment of the surrounding environment should be performed to ensure the sensitivity of the landscape, heritage and local community are not detrimentally affected by the traffic signalling installation design.

NOTE 1 An assessment of the surrounding environment can be achieved through a desktop study of the area and a risk assessment.

NOTE 2 A video survey to review traffic and other user behaviours is an example of an assessment of the surrounding environment.

3.6.3 The compatibility of traffic control equipment with existing traffic signalling installations that are being modified should be determined.

NOTE Traffic control equipment can include bus priority systems, CCTV and variable message signs (VMS).

3.6.4 Modifications to existing traffic signalling installations, records of junction history, previous assessments and any known issues should be reviewed.

3.7 The traffic signalling installation design shall define a control strategy.

3.7.1 To determine the optimal control strategy, location of the site, other existing signals, road speed and junction type should be assessed by undertaking appropriate modelling.

3.7.2 Determination of the optimal control strategy may be discussed with the Overseeing Organisation.

3.7.3 The chosen control strategy should take into account the compatibility with existing traffic signalling equipment in order to optimise functionality and performance.

3.8 The detection method shall be selected as part of the traffic signalling system design.

NOTE 1 The accessibility of the site and the chosen detection method can have an impact on the safety of the maintenance operatives.

NOTE 2 Site conditions, such as adjacent vegetation growth, can impact on the chosen detection method.

NOTE 3 Detection methods can be below or above ground.

3.9 Overall junction reserve capacity shall be a contributing factor for the chosen control strategy at the design stage to allow for future additional use.

3.9.1 The potential reserve capacity provided in the chosen control strategy should be based upon local knowledge at the design stage.

NOTE Known and planned future developments and improvement schemes can impact on reserve capacity.

3.10 The traffic signalling installation design shall promote and enable safe site maintenance and inspection.

NOTE 1 The maintenance and inspection requirements can inform the design of the traffic signalling installation.

NOTE 2 The regimes of equipment manufacturers can be used to inform the design of the traffic signalling installation.

3.11 Traffic signalling equipment shall be in accordance with the Traffic Open Products And Specifications (TOPAS) requirements TOPAS [Ref 11.N].

NOTE Traffic signal displays, road markings and variable message signs, in legal terms, are ‘traffic signs’ and subject to the UKSI 2016/362 (TSRGD) [Ref 9.N].

3.12 Traffic signalling equipment shall be selected to maintain performance, in accordance with equipment specifications, throughout its life-cycle.

3.12.1 Maintenance schedules should be assessed to ensure the performance of the traffic signalling equipment is suitable for the environment in which it is installed.

3.13 The components of the traffic signalling equipment shall be compatible with the traffic control equipment for each installation.

3.13.1 For modifications to existing installations, new traffic signalling equipment should be compatible with the existing installation.

3.14 Traffic signalling installations with pedestrian facilities must be designed to make provision for disabilities and specific age groups (elderly and children) in accordance with the Public Sector Equality Duty in the UKPGA 2010/15 Clause 149 [Ref 1.N]. In Northern Ireland the equivalent legislation is Section 75 (Statutory duty on public authorities) of Part VII (Equality of opportunity) of the Northern Ireland Act 1998 UKPGA 1998/47 [Ref 4.N]

3.15 An assessment shall be made at the design stage as to whether the interaction of the traffic signalling installation with walkers, cyclists and horse-riders is needed.

3.16 Where the interaction of walkers, cyclists and horse-riders affects the traffic signalling installation, the requirements of GG 142 [Ref 14.N] shall be met.

NOTE Traffic signalling installation measures to make provision for disabilities and specific age groups can include tactile indicators, audible signals, dropped kerbs and tactile paving.

3.17 Public transport systems that have an impact, or can be impacted, by the traffic signal installation shall be identified for integration to the system at the design stage.

3.17.1 The integration of the traffic signalling system to public transport systems should include priority measure, location and access to boarding.

3.18 All traffic signalling installations shall include a method of remote monitoring.

3.19 The traffic signalling installations shall enable the Overseeing Organisation to remotely monitor the status of the installation.

3.20 The chosen method of remote monitoring the traffic signalling installation shall allow operational and fault reporting to be achieved.

NOTE Operational and fault reporting of the traffic signalling installation can be achieved via mobile or fixed communication connection.

3.21 The need for any passive safety elements within the traffic signalling installation, including any electrical isolation system, shall be reviewed at the design stage.

3.21.1 The risk factor for passive safety elements, based on severity and likelihood, should take into account the traffic signalling installation aspect arrangements and the wind speed for the area.

This document is published by National Highways on behalf of Department for Infrastructure, Northern Ireland.

This document supersedes TA 12/07, TA 16/07, TA 56/87, TA 82/99, TA 84/06, TD 07/07, TD 24/97, TD 35/06, which are withdrawn.

This document forms part of the works specification. It does not purport to include all the necessary provisions of a contract. Users are responsible for applying all appropriate documents applicable to their contract.

This National Application Annex contains the Department for Infrastructure, Northern Ireland specific requirements related to traffic signalling system design.

The assumptions made in GG 101 [Ref 1.N] apply to this document.