My city invested in changing over street lighting to low sodium pressure only to end up replacing it all a few years later. The problems with low sodium pressure is two fold. Most objectionable is that the light source washes out color distinctions to the point that it is difficult to accurately describe a vehicle's color. The second objection relates to the difficulty of controlling the light output with the usual lens types. The low sodium pressure lights ended up producing annoying light diffusion to residences. The plus side is that this source of lighting is the most economical as the light output is very high.