Contributions of Heat from Traffic Vehicles to Snow Melting on Roads

Abstract

The heat balance of road snow was analyzed to examine ice-film formation and to determine the characteristics of heat balance on a natural snow cover. The main heat source used to melt natural snow cover is solar radiation. However, the results of the analysis indicated that the absorbed solar radiation is reduced due to the high albedo of snow and therefore cannot compensate for the heat loss by long-wave radiation. This occurrence results in negative net radiation during winter. To evaluate the heat balance on road snow, the infrared radiation from vehicles was estimated by measuring vehicle temperatures. These measurements indicated that heat input applied to snow decreased with vehicle speed and increased with traffic volume. A new index—the shading time—was developed and is defined as the amount of time a section of road is shadowed by vehicles. It was established that incoming long-wave radiation increased by 50 percent during 20 minutes of shading time and that the net radiation became positive, suggesting that snow melting occurred on roads with heavy traffic flow, even in winter.