Roadway lighting design for optimization of UPD, STV and uplight

In accordance with the new ANSI/IESNA RP-8-00, roadway lighting calculation s were made to investigate relationships between Unit Power Density (UPD), Small Target Visibility (STV), and Unit Uplight Density (UUD). Calculations were made for specific luminaires, roadway configurations and lighting system geometry for a range of mounting heights. At each mounting height, the luminaire spacing was increased until any one of the illuminanc e or luminance criteria was not met. The last spacing which meets all the c riteria (for both the illuminance and luminance methods) is the maximum for that run. As the mounting height increased over successive runs, maximum s pacing initially increased before usually decreasing. Optimum spacing typic ally occurred when the mounting height was increased until, at the greatest maximum spacing, uniformity and average criteria both reached their limit. For the same wattage luminaire, as spacing increases, UPD decreases proport ionally. Decreases in UPD correspond to decreases in UUD values. The STV va lue at the optimum spacing is typically a local maximum for that range of l uminaire spacing or UPD values. Typically, luminaires with semi-cutoff distributions produce the lowest UPD , along with low UUD and relatively high STV values. Distributions with gre ater cutoff have greater UPD and UUD values, with full cutoff distributions having even higher values. When mounting height and luminaire spacing are optimized to meet just the l uminance criteria, UPD and UUD values decrease, typically 10-20 percent. Wh en designing to the STV criteria alone, further reductions occur, between 5 -12 percent less than for the luminance criteria. This is proportionally tr ue for every category of cutoff.