Flame spread characteristics over the fuel-spilled and/or snow- covered asphalt road (both porous and non-porous) were studied experimentally from the point of view of fire hazard prevention in many fuel spill accidents on the urban asphalt road. A large scale pool burning occurs on the non-porous usual asphalt road, but flame spread and pool burning cannot occur on the porous asphalt road owing to the drainage of fuel. When the liquid fuel was spilled on the snow-covered road and ignition occurred, the liquid fuel burns on the fuel-soaked sleety snow layer. On the thick snow layer, if the amount of spilled fuel was not so large, the combustion on the fuel-spilled region cannot continue for a long time, even for highly flammable fuels such as gasoline. However, if the snow layer was not so thick, and a large amount of fuel was spilled, the sleety snow layer beneath the flame reaches the road surface with the lapse of time of combustion. The water layer due to snow-melting is formed and pool burning occurs on the exposed road surface. On the porous asphalt road, however, such pool burning cannot occur because both the water and the fuel are drained. Comparison between the flame spread rate measured on the fuel-spilled snow-covered non-porous road and that predicted by a simplified model suggested that both the mechanism of combustion on fuel-soaked sleety snow layer and the scale effect, causing a strong fire-induced convection flow, should become important factors for flame spread on the snow-covered road.
