Illumination is essential to enhance the drivers' visibility for safe operation of vehicles at night on our modern, high speed, high volume roadways. This paper will outline the tremendous technical advances that have been made in roadway lighting this century in terms of light sources, design procedures, delivery systems and mounting hardware. It will also examine and explain the why's and where's of each change as it took place. There was time when roadway lighting consisted only of extensions to the city street illumination system. Now, thanks to modern technology and the computer, we have innovations in all areas of the lighting system to better meet the driver's visibility needs. Firstly, light sources have evolved over the years from the low efficiency incandescent lamp up to the present day high efficiency High Intensity Discharge lamps. Secondly, there is an ever growing acceptance of design methodology whereby the measurement of light that reaches the pavement has been surpassed by the more sophisticated and logical process of quantifying what the driver's eyes actually see. Delivery systems have progressed from the "put light everywhere" globe - an astronomers worst nightmare - to the technologically innovative cut-off luminaire which can direct light to where it is most needed. In terms of mounting hardware, roadway lighting has progressed from being mounted on utility poles at little more than 9 meters to todays' 45 meter High Mast Poles. The move to higher mounting heights has reduced the number of poles, thus minimizing car/pole collisions and clutter and resulting in a safer roadway and a better visual environment. In these days of shrinking infrastructure funding, these innovations will assist us in meeting the challenges of enhancing the economy, advancing technology and sustaining the environment. (A)
Samenvatting