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Beyond Safety in Highway Guardrailing

Beyond Safety in Highway Guardrailing

Highway guardrailing performs a variety of important tasks in different locations.

In urban areas, guardrailing is typically used along the kerb-line of high-density shopping streets; at the entrances and/or exits to transport interchanges; at road intersections; pedestrian crossings; school entrances and exits; central reservations; and, on pedestrian refuge islands.

Guardrailing has also been introduced at a number of sites as a way of keeping vehicles off the footway and to discourage parking where there was evidence of pedestrians being masked by parked cars.

In these high traffic environments, guardrailing is used along the edge of footways to provide guidance to pedestrians, and ensure optimum safety, reducing the risk of accidents by preventing pedestrians from walking on the carriageway or crossing at dangerous places, in accordance with the Highway Code.

Beyond pedestrian usage, guardrailing features extensively on major trunk roads and motorways, helping to protect maintenance teams accessing electrical boxes at the side of the carriageway; on concrete capping beams running along the top of sheet pole retaining walls; on concrete headwalls for drainage outlets into balancing ponds; on parapets, bridges and elsewhere. These structures ensure protection for road maintenance teams accessing these areas, helping to prevent accidents and falls from height.

Guidance on Pedestrian Guardrailing (PGR)

Section 66 of the Highways Act provides powers for a highway authority to provide, maintain, alter and remove guardrailing in a highway, but no dedicated UK guidance exists to define the overall criteria for installation. Decisions are typically based on good engineering judgement in conjunction with any available guidance and in the light of local circumstances. 

To that end, the Department for Transport’s Local Transport Note 2/09 provides guidance that local authorities may choose to adopt, including a description of the development of policy guidance on pedestrian guardrailing; an assessment procedure for the evaluation of the need for the installation or removal of pedestrian guardrailing, particularly at pedestrian crossings and road junctions; and encouragement for authorities to consider developing and using an audit trail, recording decisions and actions taken when considering pedestrian guardrailing schemes.

Meanwhile, the current British Standard for pedestrian guardrailing is BS 7818: “Specification for pedestrian restraint systems in metal”. This is a technical design standard that specifies the requirements for the construction of pedestrian and other non-vehicle user restraint systems in metal for use on roads and highways. It also includes useful guidance on the layout and intervisibility of restraint systems.

Fabricated or a Tubular Guardrailing?

Of course, safety is the paramount concern for engineers. But other supporting factors also merit consideration, especially when the choice is between a fabricated or a tubular structure assembled using standard tube and fittings. Notably, ease and speed of installation, high corrosion resistance and adaptability should all figure and be assessed as part of the specification process.

When it comes to ease and speed of installation, then guardrailing constructed using standard tubes and fittings is proven to be 20% less expensive than fabricated structures.

Kee Safety has carried out a comparison study on a typical 16m structure – one assembled using standard tube and fittings from the Kee Safety range whilst the other was fabricated on site, connected using traditional welded joints.

The study shows that the Kee Safety structure provided a 41% saving in labour which contributed to an overall 20% cost reduction in assembly time. Working with a tube and fittings type solution also eliminates the hidden costs associated with fabrications, such as, the requirement for tailored fabrication drawings, extra site visits, transport and the cost of welding consumables. You can watch a video to learn more about advantages of tubular stuctures vs. fabricated structures.

Corrosion Resistance

An additional benefit of tubular structures is corrosion resistance.

The Zinc Millennium Map (1998-2000) details the background atmospheric corrosion rates of zinc across the UK and Ireland. Given sufficient time, oxygen, and water, any iron mass eventually converts entirely to rust and disintegrates, and in marine atmospheres (category 3 environments) the Map shows that untreated steel will uniformly corrode at up to 170 microns each year.

Using information from the survey, and deeming the structure unsafe following local corrosion of 25%, we have identified that the average life of a structure using corrosion resistant hot dip galvanised fittings, such as the Kee Klamp® range of fittings, will be 37 years in a category 3 town, for example, Newcastle Upon Tyne. This compares to 4.7 years for a fabricated structure, featuring a uniform 3.2mm weld.

Kee Klamp® Fittings Used in Road Safety Guardrailing

Kee Safety supplies the leading Kee Klamp fittings for a range of road safety guardrailing applications. This comprehensive selection of simple to use, galvanised malleable cast iron fittings allows pre-cut lengths of standard tubing (from 21.3mm to 60.3mm) to be quickly and easily connected together. The end result is a finished structure with uniform appearance which meets guaranteed design loads and British Standard requirements, as well as meeting high corrosion resistance demands.

All fittings within the range incorporate an integral socket screw which locks the fitting securely onto its tube to give an excellent slip load performance. The extensive range ensures that they can also cope easily with any changes in direction or gradient, and accommodate requirements for quickly adapting or extending an existing structure.

Of course, optimum road safety for pedestrians, cyclists and maintenance teams is the main driver behind the specification of safety guardrailing. However, providing a structure that is quicker and more cost-effective to assemble as well as being safer for longer will pay dividends. Ultimately, it will be cheaper in the long run as well which makes sense for highway engineers and local authorities, especially those designing structures for more testing environments, close to the sea.