A special road safety problem is Split friction or μ (mu) - split; when the friction significantly differs between the left and the right wheelpath. The road may then not be perceived as hazardous when accelerating, cruising or even braking softly. But in a case of hard (emergency-)braking, the car will start to rotate over the wheelpath offering highest grip. Split friction may cause jack-knifing of articulated trucks, while trucks with towed trailers may experience trailer swing phenomena. Split friction may be caused by an improper road spot repair that results in high variance of texture (roads) and colour (thin ice on newly paved black spots thaws faster than ice on old greyish asphalt) across the road section.
To some extent, the risk for Split friction can be measured with a road profilograph, scanning the pavement texture in both the left and right wheel paths.