Roadway Lighting Design for Optimization of UPD, STV and Uplight

摘要

In accordance with the new ANSI/IESNA RP-8-00, roadway lighting calculations 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 illuminance or luminance criteria was not met. The last spacing which meets all the criteria (for both the illuminance and luminance methods) is the maximum for that run. As the mounting height increased over successive runs, maximum spacing initially increased before usually decreasing. Optimum spacing typically 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 proportionally. Decreases in UPD correspond to decreases in UUD values. The STV value at the optimum spacing is typically a local maximum for that range of luminaire 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 greater 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 luminance criteria, UPD and UUD values decrease, typically 10-20 percent. When designing to the STV criteria alone, further reductions occur, between 5-12 percent less than for the luminance criteria. This is proportionally true for every category of cutoff.