Development of Road Lighting Technology and Dimensioning
The effects of light spectrum and luminance level on visibility in road lighting conditions were studied in experimental road lighting installations. The test room used in these measurements is an underground tunnel of 200 m length. Different road lighting installations were built in the tunnel. The spectra of the light sources was varied by using different lamp types and by using coloured filters in the luminaires. The luminance levels of the installations were varied both with neutral density filters in the luminaires and with electrical dimming of the light sources.
Visibility tests were conducted for test persons in the tunnel in order to study foveal and off-axis vision at mesopic light levels. Visibility of pedestrian was used as the visual task. In the tunnel the weather and lighting conditions remain constant. It is thus possible to carry out visibility tests with several test persons in exactly the same conditions at any time. Contrast threshold measurements with different light spectra and luminance levels were also carried out in laboratory conditions with a modified Goldman perimeter.
The work also introduced a new method for road luminance measurements. A CCD based luminance photometer has several advantages compared to conventional spot luminance meters. Luminance measurements on different types of road and street lighting and viewing conditions were made with two different CCD based photometers. The luminous distribution data was used to analyse the visual tasks and viewing conditions in night-time driving.