Skid resistance can be measured by various types of equipment, but all devices suitable for
routine use rely on measuring the forces generated when a rubber tyre or slider is dragged across
a wetted surface. The skid resistance offered by a surface is believed to be related to fine scale
texture, or “microtexture”, present on aggregate chippings and a method of measuring and
quantifying surface microtexture may therefore provide an indication of the skid resistance.
A programme of experiments is being undertaken by TRL Ltd for the Transport Research
Foundation to determine whether detailed imaging of the road surface has potential to be applied
to the determination of microtexture.
This report describes work carried out in the 2006-2007 financial year. Specimens of typical road
aggregates were photographed, using a linescan camera system, before and after artificial
polishing. Images of the aggregates in the different states of polish were examined automatically,
by developing bespoke software, to assess if a change in the microtexture could be detected and
linked to the measured change in friction on the specimen surface. The method for analysis,
including masking of the image to isolate aggregate surfaces, and the algorithms that examine
changes in image intensity, are briefly described. The correlation between parameters determined
from image analysis and friction measurements on the specimens is presented.

Want to know more about this project?