How to Organise a SCRIM® Survey

Define the Network and Strategy

• Establish a Skid Resistance Policy: Create a formal policy outlining the overall approach to managing skid resistance on the road network, including roles, responsibilities, and performance indicators.
• Define the Survey Network: Clearly identify which parts of the highway will be subject to routine SCRIM® testing (e.g. principal, strategic, and main distributor roads), often based on traffic flow and accident risk.
• Set Site Categories and Investigatory Levels (ILs): Categorise road sections based on factors such as road geometry (bends, gradients), approaches to junctions and crossings, speed limits, and accident history. Assign appropriate Investigatory Levels.

Survey Logistics

• Procure a Survey Contractor: Engage a contractor, such as WDM Limited, who can provide certified SCRIM® vehicles and data processing services. Ensure the Survey Contractor has accredited SCRIM® vehicles by checking the Roads Liaison Group website. As part of the procurement process, ask for evidence of previous accreditation and the collection and submission of ongoing QA data.
• Develop an Annual Programme: The skid resistance of road surfaces can fluctuate within a year and between successive years, while maintaining a similar general level over a longer period. By smoothing these fluctuations caused by seasonal effects, sites exhibiting lower skid resistance can be identified more accurately.
• Plan the Timing of Surveys: typically annually within specific seasonal periods (early, mid, or late summer), to allow for the calculation of the Characteristic SCRIM® Coefficient (CSC). Another approach is to use a year correlation of a single main survey run using a correction factor derived from seasonal surveys of control sites; the Mean Summer SCRIM® coefficient.
• Supply the Survey Contractor with a GIS file of the survey network.

Surveying and Data Processing

• Conduct Surveys: The survey contractor should comply with BS7941: part 1 and apply a Quality Management system for the collection and processing. SCRIM® vehicle performs continuous measurements of the road surface’s skid resistance.
• Ask the contractor to supply the accreditation certificate for the survey vehicle used to undertake the SCRIM® survey covering the period for which the survey was undertaken. If in doubt, check the Roads Liaison Group website.
• Validate and Process Data: The contractor processes the raw data, correcting for variables and speed, then calculates the seasonally corrected SCRIM Coefficients.
• Import into Asset Management System: Integrate the processed data into the highway authority’s asset management software (e.g. UKPMS / PMS) for analysis and comparison against the pre-determined ILs.

Analysis and Planning Action

• Identify Deficient Sites: Flag all locations where the measured SCRIM® coefficient is at or below the assigned Investigatory Level.
• Prioritise Investigations: Use a risk-based scoring system that combines skid resistance deficiency magnitude, crash data (specifically wet-road skid-related collisions), and other site-specific factors to rank sites for further investigation.
• Undertake Investigations: Conduct desktop and site visits to high-priority locations to confirm conditions, identify contributing factors, and determine appropriate remedial actions (e.g., surface retexturing, resurfacing, routine maintenance or installing warning signs).
• Programme Remedial Works: Schedule and fund necessary remedial works, prioritised by risk, as part of the overall network maintenance programme.
• Maintain Records: Keep detailed records of all survey results, investigations, and actions taken to demonstrate compliance and provide a legal defence in case of incidents.