Heat dissipation

Rough guess

Sunlight is radiated at the earth surface at about 100 watts/ft^2. That's about 4217 J/hr/ft^2.

Making an assumption that a single lane is 12 feet wide and it's a two lane highway that's 24 feet wide. The area per linear mile is about 5280ft*24ft about 125,000 ft^2 per mile for a heat load of 12,500,000 watts/mi or 12.5 Megawatts per mile.

Note this is a simple model for a 100% efficient blackbody blacktop that does not consider the heat conduction away from the blacktop by the earth surrounding the highway not the convection of rising air currents.

Rap