The typical payback period for retrofitting a cobrahead system with median mount fixtures is about one year. Fixture selection guidelines Median mount lighting fixtures are as applicable for new construction as they are for retrofits. This is to help assure the safety of maintenance personnel. Examine the fixtures' lighting performance in terms of uniform distribution and glare control. A lighting system that produces uniform light levels on the entire roadway will reduce eye fatigue since the eyes aren't in a constant state of adaptation from bright spots to dark spots.
Uniformity also makes the lighting more pleasing to the general public.
Proper lighting distribution will maximize efficiency, minimizing energy consumption, maintenance expense, and pole knock-downs. Numerous research studies have shown that glare has little effect on visibility, but a system that minimizes glare will likely gain the approval of the motorist more quickly than other factors. Consider the energy efficiency of the ballasts, with a goal to achieve less watts per footcandle. It is incumbent on the lighting designer to select luminaires that not only meet the requirements for photometric performance but also consume the least amount of energy to produce the required results. When analyzing electric performance data, it is important to compare the total input watts to the lamp watts.