UK roads surfaced with stone mastic asphalt (SMA) may be causing accidents. Pistonheads reports that police investigator Jim Allen tested the surface in dry conditions, performing severe braking maneuvers. Sgt. Allen discovered that his car's tires, heated by friction, melted the SMA surface. The vehicle then "surfed" on top of the molten bitumen, adding to "normal" braking distances. The problem has been acknowledged by several European countries, although only Ireland has prohibited the use of SMA on roads with a speed limit over 30mph.