PHOTOMETRIC AND COLORIMETRIC EVALUATION OF THREE CHANGEABLE MESSAGE SIGNS
Three Changeable Message Systems (CMSs) were evaluated for luminance, colour and subjective visibility. The three types involved were: 1) Telespot with fiber optic technology LYNX; 2) Ledstar CMS (LED); and 3) Fortran SYLVIA (fiber optics). Measurements were made in both laboratory and field settings using the Pritchard Photometer (for luminance and colour specifications) and the Minolta Chromameter (for illuminance and colour temperature of ambient daylight). Visibility and conspicuity were derived theoretically by calculating critical ratios for figure (pixel) and background (mid-grey) and practically by recording observer preferences and photographing at three distinct viewing distances (100, 200, and 300 meters). Photometric data from laboratory measurements indicate that the Telespot "day overbright" setting had the highest luminance value (873,000 cd/sq m) and Ledstar green and red had the lowest (10,190 cd/sq m). Field data are much lower for all CMS displays as these measurements include the total pixel. Luminance was highest for Fortran (45,600 cd/sq m) and again lowest for Ledstar (green at 4,700 cd/sq m). These luminance values include the ambient illuminance which was twice as high during the Fortran measurement as it was for Telespot (120,000 vs 60,000 lux). Laboratory measurement of Telespot single fiber shows the typical logarithmic relationship that exists between voltage and light intensity; the luminance at 10.8 volts was 330,000 cd/sq m for one lamp and 632,000 cd/sq m for both. Ledstar colours are red with a lambda D of 700 nm, green with lambda D 575 nm and amber with lamba D 603 nm. The Fortran colour is about lambda D 591 nm to 593 nm and is invariant with intensity or ambience. There are differences between laboratory and field measurements for Telespot and small variations with voltage settings, where the pixel appears green in the field and yellow in the laboratory. The practical study of observers' responses and the photographic evidence indicate that at close range (100 m) all signs are clearly seen while at greater distances, particularly 300 m, a clear rank order emerges with Telespot the most visible, Ledstar next and Fortran least visible.
TELE-SPOT Display Systems IncorporatedOne Atlantic Street
Stamford, CT United States 06901
- Lakowski, R
- Publication Date: 1991-12
- Features: Figures; Photos; Tables;
- Pagination: 47 p.
- TRT Terms: Colorimetry; Field tests; Laboratory tests; Luminous intensity; Photometry; Variable message signs; Visibility
- Subject Areas: Highways; Operations and Traffic Management; I73: Traffic Control;
- Accession Number: 00622417
- Record Type: Publication
- Files: TRIS
- Created Date: May 31 1992 12:00AM