When it comes to highway and infrastructure projects, earthworks performance is critical to long-term structural reliability. To manage this risk, engineers across the UK rely on the Specification for Highway Works (SHW), a framework that defines how materials must be selected, tested, and verified before use.
A key element of this framework has traditionally been Series 600, which governs earthworks construction and material suitability. Following the September 2025 update to the Manual of Contract Documents for Highway Works (MCHW), these requirements are now consolidated under CC 601, introducing a clearer structure while maintaining rigorous testing expectations.
In this guide, we explain what SHW Series 600 (now SHW CC 601) involves, why it’s important for highway engineering and wider construction projects, and how comprehensive laboratory and site testing helps project teams ensure compliance, manage risk, and deliver durable infrastructure.
Key Takeaways
- SHW Series 600 Earthworks has been replaced with CC 601, aligning with updates to the Manual of Contract Documents for Highway Works (MCHW).
- While primarily for roads, Series 600 SHW (now CC 601) is considered the default benchmark for residential and commercial earthworks across the UK.
- Comprehensive testing under CC 601 helps prevent structural failures in highway and infrastructure projects by ensuring all materials meet specific performance criteria.
- Working with UKAS-accredited partners like CTS ensures your results are traceable, accurate, and ready for regulatory audits.
- CTS provides bespoke testing packages that align with the latest Series 600 highways requirements across the entire project lifecycle.
Introduction to the Standards for Highways
The Specification for Highway Works (SHW) – Volume 1 of the Manual of Contract Documents for Highway Works (MCHW) – comprises a detailed set of specifications developed by National Highways (formerly Highways England / Highways Agency).
These documents govern the design, construction, and maintenance of the UK road network to ensure consistency, safety, and sustainability. For infrastructure teams, local authorities, and town planners, these standards represent the professional benchmark for quality assurance.
From Series 600 SHW to CC 601: What’s Changed?
The Specification for Highway Works (SHW) Series 600 is a technical specification within the MCHW that defines requirements for excavating, filling, and compacting earthworks on highway projects. It classifies material suitability and sets standards for slope construction, drainage, and fill placement, helping to ensure safety and quality.
Because it provides such a comprehensive framework, SHW Series 600 has become the default earthworks specification across the UK, frequently applied to residential and commercial developments. While the series remained largely unchanged for more than thirty years, it was revised in September 2025.
The core earthworks requirements are now set out in CC 601 (Earthworks), supported by CP 601, which provides instructions for specifiers. This update replaces legacy documentation with a clearer, more consistent structure to improve contract preparation, reflect current industry practice, and align with the updated Design Manual for Roads and Bridges (DMRB).
Technical Testing Within CC 601 (Formerly Series 600)
Within the MCHW, Series 600 (now CC 601) sets out the performance requirements that earthworks materials must meet before they can be used in highway construction. These requirements help engineers determine whether a material is suitable for its intended purpose, from general fill and drainage layers to structural support beneath heavily trafficked roads.
Because material performance cannot be reliably assessed through visual inspection alone, laboratory and on-site testing are essential for compliance with the specification. Testing provides the technical data needed to confirm properties such as strength, moisture behaviour, compaction potential, and long-term durability.
At CTS, our independent laboratories and site teams support earthworks testing across a wide range of material classifications. By analysing how materials respond to loading, weather conditions, and construction processes, we help project teams make informed decisions, manage risk, and maintain progress throughout the project lifecycle.
Acceptable Earthworks Materials
To apply the performance requirements set out in SHW CC 601 (Series 600), earthworks materials are first classified according to their intended use and physical characteristics. This classification helps engineers determine where a material can be used within a highway scheme and what level of testing is required to demonstrate compliance.
Take a look at the full list here.
Types of Testing
CC 601 (Series 600) defines both laboratory and on-site testing procedures, which together provide the evidence needed to approve materials for use and verify that earthworks are performing as expected during construction.
At CTS, we deliver the full range of testing required under the standard, generating the technical data that engineers and project managers rely on to support design decisions, maintain quality control, and keep projects moving. Key tests include:
Specialist laboratory testing:
- Particle size distribution test
- Plasticity index
- Moisture condition value (MCV)
- SMC and IDD of chalk
- Undrained shear strength
- Optimum moisture content, rammer and vibration
- California bearing ratio (CBR) test
- Los Angeles
- Small and large shear box
- Permeability
- Chemistry (sulphates, chlorides, pH, etc.)
On-site performance testing:
- End compaction – maximum dry density (nuclear, sand replacement, core cutter)
- Moisture condition value (MCV)
- Degree of pulverisation
- California bearing ratio (CBR)
- Hand shear vane
- Dynamic Cone Penetrometer (DCP)
- Light Weight Deflectometer
Why CC 601 Testing is Critical for Success
SHW CC 601 (Series 600) testing plays a central role in ensuring projects meet design expectations, regulatory requirements, and long-term durability targets. Key benefits include:
1. Safety and Structural Reliability
Rigorous testing identifies potential weaknesses in earthworks before they can lead to structural failure. By ensuring only compliant materials are used, SHW CC 601 helps infrastructure teams build road networks that can withstand heavy traffic loads and environmental pressures for decades.
2. Performance and Suitability
SHW CC 601 allows engineers to match the specific characteristics of a material to its intended application. Testing confirms whether a material has the necessary load-bearing capacity or resistance to frost and moisture, ensuring long-term performance in the field.
3. Quality Control and Cost Management
SHW CC 601 testing serves as a primary quality control mechanism. Detecting non-compliant materials early in the construction process prevents the need for expensive remedial work or project delays. It provides the "right first time" assurance that project managers require.
4. Regulatory Compliance
Following the Specification for Highway Works (SHW) promotes consistency across the industry. It ensures that every stakeholder, from the developer to the local authority, can be confident that the infrastructure meets national benchmarks for quality and accountability.
Choose CTS for Market-Leading Expertise
Delivering compliant earthworks under SHW CC 601 (formerly SHW Series 600) depends on reliable testing data, experienced interpretation, and consistent quality assurance throughout the project lifecycle. Independent materials testing helps teams confirm suitability, demonstrate compliance, and maintain confidence in construction outcomes.
CTS is dedicated to helping our clients solve complex earthworks challenges through technical excellence. We verify compliance with the WRAP (Waste and Resources Action Programme) Quality Protocol and support the latest updates to the Specification for Highway Works (SHW) Series 600, including the transition to CC 601.
Our routine sampling and testing services cover quarried, recycled, and IBA aggregates. With a network of UKAS-accredited laboratories, we provide the independent, traceable results you need for approvals, audits, and quality assurance. Whether it’s support for earthworks under CC 601 (Series 600), drainage under CC 500 (Series 500), or unbound pavements under CC 201 (Series 800), our team is ready to assist.
FAQs
What is the difference between Series 600 SHW and CC 601?
CC 601 is the updated designation for the earthworks specification within the Standards for Highways. It replaces the legacy MCHW Series 600 documents. While many of the technical testing methods remain consistent, the new structure improves clarity for contract preparation and reflects modern engineering standards.
Is Series 600 testing mandatory for residential developments?
While the Specification for Highway Works (SHW) was developed for national road networks, the SHW 600 Series (now CC 601) has become the industry-standard specification for almost all UK earthworks, including housing and commercial schemes. Local authorities and inspectors typically require evidence of compliance with these standards.
How does the September 2025 update affect current projects?
The new CC 601 and CP 601 documents apply to all new schemes moving forward. They replace the older Series 600 versions that have been in use for the last 30 years. CTS can help you review your current testing schedule to ensure it aligns with these modernised requirements and the updated method of measurement for highway works.