ACO | Six-Part Series – Part 2 | Sharing the Load: Understanding Load Classification for Better Highway Drainage

In part two of this new six-part series, authored by Terry Wilkinson, Specialist Design & Application Engineer at ACO Water Management, we look at how to take a water positive approach by focusing on load classification and how it helps engineers create sustainable highway drainage systems.

Specifying drainage channels with the appropriate load class is a key part of developing successful highways projects. Highways and infrastructure engineers will recognise its significance for avoiding potential dangers and designing out risk in highway development projects.

Engineers will also be familiar with the fallout of incorrect drain specifications when dealing with the resulting economic and environmental losses incurred from uncontrolled surface water. Yet, despite the widely acknowledged importance of correct load classification by industry professionals, there still appears to be some confusion among engineers when navigating the specifications for certain highway projects.

In a survey by ACO of 100 highways and infrastructure engineers, just over half (56%) agreed that they fully understand the specification needs for highways works in relation to linear drainage channel and combined kerb drainage load classification. Interestingly, only 28% ‘strongly agreed’, with the other 28% only ‘somewhat agreeing’.

The Manual of Contract Documents for Highway Works (MCHW) and Design Manual for Roads and Bridges (DMRB) are the go-to reference points for engineers when considering the drainage required for specific systems. But there are other considerations to keep in mind.

This is because design standards vary between locations and road types when designing a new system. As a result, an in-depth understanding of load classification should be cross-referenced with each project’s design requirements.

Navigating Load Classification and Avoiding Misunderstanding

The complexity of highway projects requires engineers to have a broad understanding of possible drainage problems and their solutions.

If system failure and highway disruption are to be minimised, the load class of drainage channels needs to be based on traffic and application. Otherwise, what could happen is the drainage channel fails prematurely, and sunken or damage drains then causes the surrounding environment to suffer, and the natural water cycle to be disturbed.

The knock-on effect is that surface water is not managed in the way that it was intended, potentially causing unsafe conditions for motorists and highway users. Not only this but it creates additional and unnecessary costs.

By developing a strong understanding of load requirements, engineers can confidently design out risk and choose the best drainage solution for their project. That being said, there is also an element of interpretation involved when choosing drainage channels and the load class they should meet.

This is where highways engineers should seek help from water management companies, such as ACO, which can take the guess work out of choosing load specifications and equip engineers with tailored advice and techniques moving forward in project design. This includes the provision of technical drawings, hydraulic calculations, and AutoCAD detailing.

As well as getting confident with identifying and managing load class specification, engineers should look to maximise their water positive highway designs through a holistic approach to drainage solutions. In upcoming editions of this series, we will talk further about other areas of highway design such as software tools and product application while providing best practice advice.

For more information on ACO Water Management and its range of drainage and water management solutions, click here.