Highway Sign – Ross Atkin Associates

The Highway Sign is a support for temporary road signs. It is made from recycled plastic (in a closed-loop system) and replaces a steel A-frame and sandbag, reducing both the manufacturing and usage carbon emissions and the negative impacts on street users.

P.F. Cusack

P.F. Cusack (Tool Supplies) Ltd are a manufacturer and supplier of roadworks equipment. They are the UK’s leading stockist of these items with five depots around the country supplying contractors working for most of the utilities and many local authorities.

Background

The brief for this project was to replace the small steel A-frames and sand bags that are commonly used to support temporary road signs on low-speed roads and streets, in particular those in urban contexts. Our own work, doing both general on-street shadowing research with disabled people, and specific roadworks-focused research in the development of the Sight Line System, had identified several ways these signs negatively impact street accessibility. Ongoing work by Michael Barratt MBE at Transport for London (TfL) focused on engagement with disabled people to remove accessibility barriers created by roadworks had also identified a series of issues associated with the use of A-frames and sandbags on London’s streets. These issues are:

Long cane users can easily get their canes trapped (and possibly broken) between the legs of the A-frames (or any sign that doesn’t have either a continuous base or a tapping rail at a low level between the legs).
The sandbags can fall off, presenting a trip hazard and meaning the sign falls over (another trip hazard + missing sign).
The weight of the sandbags depends on how much sand was put in so there might not be enough weight to resist the wind loading causing more falls (2).
If the A-frames end up left on the street with no sign face on they are difficult to see and can do serious damage to any cyclists or motorcyclists that hit them. I’m aware of at least one fatality.
The A-frames take up a large amount of space on the footway restricting movement around them.

The A-frames, which are scaled-versions of the huge ones used on Motorways, had become widely used for two reasons:

Safety auditors are asking for signs to be positioned higher up (so they are not obscured by taller SUV-type cars).
Requirements for more and different kinds of signs mean that the companies setting lots of them up prefer to use signs where different sign-faces can be fitted to a single support.

Materials

As well as reducing the negative impacts of use of the sign supports on street users, we were also keen to reduce the impact of both manufacture and use on carbon emissions. To do this we selected materials that could be reclaimed from existing traffic management products that Cusack could get back from their customers at end of life.

This process is much more straightforward for a company like Cusack, operating in an industry where they sell thousands of units to a handful of customers, than it is for consumer products where companies typically sell a handful of units to thousands of individual customers. Cusack have built a recycling plant where used roadworks cones, signs and barriers are received, separated by material and ground up, with different materials sent to different manufacturing plants to be made into new products.

Development

The key design and development challenges were:

Producing a base that would minimise its negative impact on footway users, whilst providing an adequate footprint and ballast to resist overturning due to wind.
Producing a support structure that was compatible with the thousands of existing sign faces currently in circulation but could be easily manufactured by blow moulding.

We settled on a design comprising two blow-moulded components (a post and piece with arms) and an injection moulded base, profiled internally to allow multiple bases to be stacked on a post to support larger sign faces in high winds.

Getting the design right required two visits to the wind tunnel at the Building Research Establishment and lots of advice and design reviews from the lovely people at the blow moulding factory to understand the intricacies of designing for that process.

Impact

Highway signs were piloted for eight weeks from January 4th 2024 by Murphy’s and Thames Water on and around Palmerston Road, a high footfall area and major bus corridor, in the London Borough of Waltham Forest. The period of the trial included storms Isha and Jocelyn which included gusts up to 50 kt (58 mph). Of 40 signs deployed there was only a single fall, on the night with the highest winds.

“Overall view from site that this is a game changer as no sandbags are required – they look good on site and the performance on site was exceptional given the location we had set the signage up. It is easy to assemble and to dismantle – it increases our capacity to carry more equipment and reduces our risk where sandbags due to lack of filling, spillage or managing the supply of them. This is an outstanding product.”

– Murphy’s / Thames Water Trial Report

A Life Cycle Assessment conducted on the Highway Sign, based on manufacturing the units primarily from recycled traffic cones and barriers (or end-of-life Highway Signs) indicated that manufacturing each unit emits the equivalent of 3.7kg of CO2 emissions (These are primarily generated by the electricity used in the manufacturing process and so will drop as the UK electricity grid decarbonises). The A-frames it replaces contain 12kg of steel, with the manufacture of this alone emitting the equivalent of 21.2 kg of CO2 emissions. This means purchasing a Highway Sign instead of a steel A-frame provides an 83% reduction in manufacturing carbon emissions.

In addition each Highway Signs is 49% lighter than the steel A-frame and (correctly filled) sandbag, which leads to a reduction in CO2 emissions of just over 1g for every mile it is moved in use. The reduced weight means more signs can be carried on a vehicle, halving the number of vehicle movements (and the associated externalities) to set up a large job.