Technical Advisory Services for Traffic Speed Road Network Surveys

The structural condition of the strategic road network (SRN) is one of the fundamental indicators used to both plan and budget for the annual maintenance programme. Traditional methods for the collection of routine structural condition data use devices that operate at slow speed and require lane closures.

However, at the network level on the Strategic Road Network these have been replaced with a traffic-speed alternative called the 'Traffic Speed Deflectometer' (TSD). Routine network level structural condition surveys of the SRN with the TSD were implemented in 2010 under the TRASS (Traffic Speed Structural Condition Survey) contract.

TRASS is an end-result contract under which National Highway's TSD equipment is operated by a Consultant to deliver data to a specified format on defined lengths of the network. Technical support to the equipment and the survey, including quality assurance checks, are provided by a separate Consultant, called the Technical Advisor/Technical Auditor.

Following the success of the first network survey in 2010, further surveys were commissioned, as TRASS2 and TRASS3. TRASS4 commenced 2024 continues these routine surveys. In 2019 Highways England commissioned the construction of a successor to the TSD, which has been named SATTS (Structural Assessment Tool at Traffic Speed).

The device is a new generation of Traffic speed Deflectometer developed for National Highways by Greenwood Engineering of Denmark. It contains an advanced multi doppler laser measuring system that is capable of measuring in both nearside and offside wheel paths. The device was delivered in 2020, after which it was subject to acceptance testing and adaptation to support the research programme.

The acceptance was completed in early 2021 and research work has been progressed. The research work has demonstrated that the device is capable of delivering more detailed survey data and benchmark testing has been undertaken against the original National Highways TSD. Following the decommissioning of the TSD, the SATTS device is now utilised to deliver network surveys in the TRASS4 contract which commenced in 2024.

To provide independent assurance of the quality of the TRASS4 surveys, and safeguard the Company's SATTS equipment, National Highway's will commission a Technical Advisor/ Technical Auditor with responsibility to store and maintain the SATTS device (when not undertaking network surveys) and undertake Quality Assurance and Accreditation.