A new luminance calculation method that accounts for mesopic vision and fog penetration ability is presented. This method aims to select a suitable light source for street lighting and is obtained using the mesopic luminance calculation and transmittance calculation methods at each individual wavelength. Additionally, the new method was evaluated using six LED light sources between 3500 and 6000 K. Overall, the calculation results indicate that suitable LEDs' CCT decreases with an increase of luminance for low transmittance rates. However, for high transmittance rates, high CCT LED lamps are the most suitable for street lighting. The recommended CCT of LED light sources for street lighting under different visibility and luminance conditions is presented.