The IESNA is the most recognized technical authority on illumination. The mission of the Society is to advance knowledge and disseminate information for the improvement of the lighted environment to the benefit of society. This organization has been around for over ninety years.
It is our understanding the RTAC lighting levels have not been updated since the mid 1980s at which time they were adapted from IESNA. RTAC has not kept pace with the changes in lighting philosophy that have taken place since that time.
IESNA recommended lighting levels are lower than RTAC for the same road classifications (see 5.4). Therefore fewer streetlights are required per unit length of roadway (see 5.5). This lowers the capital and operation cost.
UtiliCorp Networks Canada has recently standardized on IESNA guidelines as their minimum requirement for lighting. This allows the municipality to achieve a more practical lighting design and minimize their liability.
The longer spans between streetlights fit better into the layouts of today’s subdivisions.