Southampton Road Recycling Programme

Southampton City Council was facing a familiar challenge across parts of its network: roads requiring resurfacing every five years, despite repeated investment. 100mm thin asphalt overlays were addressing surface condition, but not the underlying problem of failed foundations.

Working with BBLP in Southampton, Roadways suggested a design review and instead of repeating 50–100 mm resurfacing every few years, Roadways delivered a 315 mm standards-compliant reconstruction, including a strengthened ex-situ HBM foundation, for the same overall cost and programme duration. By addressing the failed structure rather than the surface, the scheme achieved materially lower whole-life risk and industry benchmarking indicates up to 60–70% lower embodied carbon compared with traditional deep reconstruction.

The Challenge

Historic construction in Southampton meant much of the existing asphalt was contaminated with coal tar, classed as hazardous waste. This meant removed asphalt could not be recycled through conventional hot asphalt processes and excavated material was typically sent to landfill as a hazardous waste at significant cost instead. This made deeper layers reconstruction unaffordable within the available budgets.

As a result, roads were being resurfaced with 50-100mm of new asphalt as a short-term measure. Repeatedly resurfacing roads with failed foundations is no longer technically or environmentally defensible at network scale. It drives repeated disruption, unnecessary waste and carbon while failing to resolve the root cause of deterioration. In urban streets constrained by services, a more intelligent and standards-compliant approach was required, one that improved structural performance without excessive excavation.

Beyond cost and disruption, the existing approach carried escalating risk. Tar-bound asphalt created a hazardous waste disposal liability, reliance on landfill introduced regulatory and commercial exposure, and repeated thin resurfacing increased programme risk and whole-life maintenance uncertainty.

Consequently, the client required a solution that reduced risk, whole-life cost, disruption and remained fully compliant with the operative Specification for Highway Works, including legacy Series Clause 948/BS references where applicable, or equivalent provisions in the updated 2025 MCHW, and could be delivered with cost and programme certainty.

The Roadways Solution

Roadways proposed a deep road recycling approach that worked within existing specifications rather than departing from them. By rethinking logistics, material handling and foundation design Roadways delivered a full foundation rebuild for the same overall budget previously spent on repeated resurfacing.

The existing tar-bound asphalt and failed foundation layers were removed and back-hauled to Roadways’ Sussex depot using vehicles that would otherwise have returned empty. The material was processed through Roadways’ fully computerised recycling facility and reused within HBM / CBGM foundation layers, blended with cement and GGBS. This approach enabled reconstruction to an optimised and controlled depth of approximately 315mm, sufficient to achieve the required structural performance with fewer layers and significantly less excavation than a traditional full reconstruction (typically ~ 700mm) before the application of a thin asphalt surface course.

Materials were processed and produced at Roadways’ fully-computerised recycling facility inSussex, supporting efficient delivery across the South East of England.

As a result of carrying out the correct engineering and not patching symptoms, the sustainability of the scheme was exceptional. This was as a direct result of solving the root cause in the foundation failure, reducing unnecessary excavation in urban streets with buried services, recycling site-won materials into structural layers and avoiding landfill and virgin aggregate.

By converting hazardous waste liability into a controlled and certified construction material, the solution reduced disposal risk, removed landfill dependency and delivered a structurally durable outcome within accepted standards. Industry research and materials-only benchmarking indicate that recycled HBM/CBGM foundation solutions can deliver around 60-70% lower embodied carbon compared with traditional full depth (~ 700mm) reconstruction. This is driven by the elimination of landfill, avoidance of virgin aggregate and reduced material movement.

The methodology was based on established UK specifications and accepted material standards. No departures, trials or experimental techniques were required, and quality was maintained through controlled production and testing.

Delivery Outcomes

• 100% of excavated materials reused within the new road structure

• Reduced construction layers and controlled excavation depth

• Strong quality assurance through controlled production and testing

• Faster delivery despite curing requirements

Commercial and Programme Performance

• Spencer Road delivered at approximately £250k

• Ozier Road delivered at approximately £300k

• Up to 40% cost saving compared with traditional reconstruction

• Programme shortened by around three weeks on Spencer Road

• Reduced disruption for residents and road users

Carbon and Resource Outcomes

• Zero material sent to landfill, despite tar contamination

• Over 1,400 tonnes of waste diverted from landfill

• More than 1,250 tonnes of virgin aggregate avoided

• Elimination of empty return trips through back-haulage

• On the Spencer Road scheme alone, over 11.5 tonnes of CO₂ was saved from materials production and waste disposal avoidance, driven by recycling ex-situ 100% of site-won materials into HBM foundation layers and eliminating landfill and virgin aggregate import

Following the successful delivery of Spencer Road and Ozier Road, the same standards-led recycling approach has been repeated across multiple schemes in Southampton, forming a wider road recycling programme delivered repeatedly without changes to standards, need for bespoke approvals, or altered delivery models.

This project showcases how applying existing standards intelligently can reduce cost, risk and disruption while delivering durable highway infrastructure. By focusing on logistics, materials and foundation performance, rather than increased spend, Roadways delivered a solution that is commercially credible, specification-compliant and proven at scale.