Sideway-force Coefficient Routine Investigation Machine (Briefing)

The majority of surface dressing being carried out across Devon is due to the failing of

skid resistance which has been identified through SCRIM® ..... So what does that mean?:-

SCRIM® stands for Sideway-force Coefficient Routine Investigation Machine. It is a specialized road survey system used primarily in the United Kingdom (and many other countries) to assess the skidding resistance of road surfaces12. Here’s how it works:

1. Purpose:

• The SCRIM® road survey helps measure the wet skidding resistance of a road surface. By assessing skid resistance, authorities can take proactive measures to reduce accident rates.

• Skid resistance is particularly crucial during damp or wet conditions, as it affects vehicle traction and braking performance.

1. Measurement Principle:

• The SCRIM® machine uses the sideway force principle to measure skid resistance.

• Here’s how it works:

• A freely rotating wheel with a smooth rubber tire is mounted mid-machine in line with the nearside wheel track of the vehicle.

• The wheel is angled at 20° to the direction of travel.

• A controlled flow of water wets the road surface immediately in front of the test wheel.

• As the vehicle moves forward, the test wheel slides along the surface, measuring the frictional forces.

• The resulting data provides insights into the road’s skid resistance.

1. Data Analysis and Reporting:

• The raw data collected using SCRIM® is analysed using specialized computer programs.

• The key output is the sideway-force coefficient (SFC), which quantifies skid resistance.

• Two common metrics derived from SCRIM® data are:

• Mean Summer SCRIM® Coefficient (MSSC): Calculated from three test runs spread evenly throughout the testing season.

• Characteristic SCRIM® Coefficient (CSC): Obtained by testing three different seasons over three years1.

1. PTS and SCRIM®:

• PTS (PTS International Ltd) operates SCRIM® vehicles for various clients, including Highways England and local authorities.

• PTS completes surveys on motorways, major A roads, and urban networks, covering approximately 17,000 km of lanes annually.

• Their cloud-based software allows data to be viewed promptly after collection, improving road safety by identifying deficient sites sooner.

In summary, SCRIM® plays a vital role in maintaining road safety by assessing skid resistance and informing maintenance decisions.