As part of its regular contribution to Highways magazine, the Institute of Highway Engineers (IHE) takes a look at new guidance on passive safety for Intelligent Transport Systems equipment.
The IHE's Passive Safety Electrical Guide 2021: Electrical requirements for passively safe ITS roadside installations to BS EN 12767 was written by Alistair Gollop FIHE MIET (pictured).
The passive safety guidance document was produced to assist highway and road authorities, consultants and contractors who design and implement roadside ITS equipment deployments, such as traffic signals. It is an advisory best practice document, to provide guidance regarding the implications that are posed by the electrical safety requirements for the majority of passively safe ITS roadside installations. It should be read in conjunction with BS EN 12767:2019 Passive safety of support structures for road equipment.
The necessity for the IHE Passive Safety Electrical Guide 2021 has been heightened due to changes in the current version of the BS EN 12767 standard, which no longer includes electrical requirements in the National Annex.
Due to the complexity of cable arrangements found in typical ITS installations such as traffic signals, this omission poses potential problems to practitioners undertaking the design, specification or management of ITS equipment. It is not unusual to have a mix of cable types with multiple cores for numerous electrical circuits within roadside equipment.
The guide examines why impact electrical isolation (IEI) systems should be considered when designing any roadside ITS installation, including those mounted on passively safe or traditional structures. It looks at why an IEI system may be required in addition to standard electrical protective devices, the different types of IEI solutions, which are commercially available in the UK, and how the selection of the type of pole and column should influence the IEI technology used.
Using real world examples, it illustrates these issues and sets out best practice solutions for the provision of IEI implementations for different classes of passively safe structures. It also examines underpinning issues such as effective risk assessments, extra-low voltage (ELV) installations and other supporting infrastructure which should be considered while designing installations to provide an effective overall package that works as expected if hit by a vehicle.
The vision of the IHE is simply ‘to be the Institute of choice for Highway Engineers’ and has been registering engineers and technicians with the Engineering Council since 1972 and accrediting academic courses since 1989.
Its mission is to provide professional development opportunities, support and leadership for individuals to achieve and maintain professional recognition.
As part of this approach, the Institute has published a range of guidance documents which cover a diverse range of topics.
The new Guide joins other recent publications, such as the Sign Structures Guide 2021 and the Traffic Control and Information Systems documents which are available to freely download from the Institute of Highway Engineers website.
Alistair Gollop is a long-term proponent of passively safe roadside ITS installations, due to his work on the strategic road network in England, where he has witnessed the issues associated with vehicles striking traditional steel poles and columns. Because of this, he was part of a ‘crash friendly’ initiative at Mott MacDonald and UK Roads, where the ‘Passive Revolution’ undertook a large number of real crash demonstrations for both traditional and passive structures, as part of an educational programme to provide highways engineering practitioners with examples of how these different types of structures perform when struck by vehicles.
During this time, Alistair wrote the 'Electrical Connections for Traffic Signals' chapter within David Milne’s Designing Safer Roadsides – A Guide for Highway Engineers Manual which was published in 2008.
Above: a passively safe traffic signal pole struck by an errant vehicle Impact sensor within a cable termination enclosure in a passive traffic signal pole
