Like the difference between sneakers gripping a gym floor and boots sliding on black ice, this measures how much one surface resists sliding against another. In crash analysis, it helps estimate how well tires held the road, how quickly a vehicle could stop, and whether a driver likely skidded, spun, or lost control. A higher number usually means more grip; a lower one means a slicker surface and longer stopping distance.

That matters because insurers and defense experts often build their story of a wreck around speed, braking, and road conditions. If they use the wrong coefficient of friction for wet pavement, gravel, slush, or worn asphalt, they can make a driver look faster, less careful, or more at fault than the evidence really supports. On rural Maine roads, where the Maine State Police may be working a scene far from specialized reconstruction support, early assumptions can harden into the official version.

For an injury claim, this number can affect liability, comparative negligence, and damages. It may be tied to skid marks, tire condition, weather, and roadway maintenance records. Along coastal stretches of US-1, dense fog can already complicate visibility; if the road was also damp or slick, a disputed friction value can become a major battleground. A careful review by an independent expert may expose a weak insurance denial or a flawed accident reconstruction.