A New Era for the MCHW: Empowering Innovation While Upholding Safety Standards

For decades, the Manual of Contract Documents for Highway Works (MCHW) has been the cornerstone of how we design, build and maintain England’s motorways and all-purpose trunk roads.

It has long provided a rigorous, prescriptive framework to uphold safety and performance, yet, in doing so, it has often constrained the industry’s ability to innovate, particularly when it comes to embedding sustainable practices.

With many structures in our road network dating back to the 1960s and 70s, the time for change has come. In collaboration with Transport Scotland, the Welsh Government and the Department for Infrastructure in Northern Ireland, National Highways has ushered in a newly updated MCHW – one that reflects the urgent need for innovation, flexibility and carbon reduction across the UK’s strategic road network.

Complex Challenges Require Creative Solutions

The UK’s highway infrastructure faces mounting challenges from ageing assets to rising environmental pressures and increasingly complex engineering requirements. A modernised MCHW is central to solving these problems.

The development process was a sector-wide effort, involving consultation with more than 100 organisations. The outcome is a streamlined, digitally accessible suite of specifications designed to support best practice, enable alternative materials, and remove barriers to modern construction techniques, all while maintaining the rigorous safety standards on which the MCHW was built.

What’s Changed in the New MCHW?

The revised MCHW introduces:

• Rationalised specifications with clearer roles for constructors and specifiers.
• Full alignment with the Design Manual for Roads and Bridges (DMRB).
• Compatibility with multiple contract types and procurement models.
• Integration with digital tools and machine-readability, improving accuracy and efficiency in contract documentation.
• New contract specification templates, enabling smarter project planning and execution.

These updates ensure the MCHW remains future-ready supporting innovation, while safeguarding delivery.

Driving Down Carbon Through Specification

One of the most significant developments in the new MCHW is its embrace of lower-carbon materials. Updated pavement specifications now promote sustainable alternatives such as:

• Stone Mastic Asphalt (SMA): A new prescriptive SMA specification, using specific polymer-modified binders, offers enhanced durability and longer service life, yielding whole-life carbon savings.

• Cold Recycled Bound Material: Now approved for use in high-traffic areas, this material enables in situ recycling, minimising transport and energy demands, and delivering substantial carbon reductions.

Importantly, these materials have already undergone successful trials across the strategic road network, reinforcing confidence in their performance and durability.

Performance-Based Flexibility: A Fundamental Shift

The move towards performance-based requirements allows contractors to meet essential safety and durability outcomes while choosing the most efficient, low-carbon methods and materials. Examples include:

• Earthworks specifications now focus on outcomes such as strength, stiffness and hydraulic conductivity, enabling greater flexibility in how these are achieved.

• Backfilling standards for retaining walls now allow work to proceed once structural strength is achieved, replacing the previous fixed 14-day delay.

This flexible approach supports the industry’s drive towards net zero carbon emissions by 2040 across all construction and maintenance activities.

Opening New Market Opportunities

Beyond the technical benefits, the updated MCHW is also about unlocking opportunity. By reducing prescriptiveness, the specification opens the door to more competition, innovation, and market diversity. Contractors are now better placed to showcase new methods and approaches, creating a healthier, more forward-looking supply chain.

The road network is vital to the UK economy. As the demands on it evolve, so too must our frameworks for delivering improvement. The new MCHW provides a foundation not only for safer and greener roads but for an industry culture that prizes ingenuity, collaboration and sustainable progress.