Did you know that Mounting Heights and Bowl Diffusers affect the Maintenance Factor of Road Lighting Luminaires? In a December 2008 Report done by Mott MacDonald County Surveyors Society, they have found that road lighting fixtures with deep bowl covers accumulate more dirt than flat glass covered luminiares. Also they have found that luminiares lower than 6 meters gets more dirt accumulation than those mounted greater than 7 meters high.
The Report is deemed very important because an incorrect assumption of Maintenance Factor can cause an overdesign in Road Lighting. The Table below shows that if such a road scheme was designed with a MF of 0.80 instead of 0.75, a substantial savings in initial cost, power consumption and maintenance could have been achieved.
The consideration of these factors in your road lighting deisgn will play an important factor in actual site conditions especially for software users where a suggested MF is often used by designers. Nevertheless, this is still being studied by professional bodies until it is ratified as a standard.
You can read the whole document here: http://www.mediafire.com/view/?upy95qbdpy8bwug