Dynamic road markings : photometric measurements and road users survey. On the motorway A44 a test was conducted with dynamic road markings (DRM). DRM consist of a line of light sources which are mounted in the pavement and can be switched in three different states: as continuous line, as interrupted line and switched off. Five markings of five different manufacturers were tested. The goal of the test is the evaluation of the technical usability of the DRM, including the testing of light and visibility aspects. By order of the AVV Transport Research Centre of the Ministry of Transport, Public Works and Water Management, we examined the photometric properties, comprehensibility, appreciation, and behavioural effects of the DRM. The results should gain an insight into the state of the art of the DRM technology, the possible application of DRM as a replacement for normal road marking, and the development of requirements for DRM. The study consists of overview measurements, detail measurements, and a road users survey. The overview measurements were made during almost nine months, with a luminance camera mounted in a driving car. Luminances and contrasts of the DRM were measured in various weather and light conditions. The detail measurements were conducted in the lab. The old markings were installed up to 308 days in the pavement of the A44. The road users survey was conducted on the road. After subjects drove the test route they were asked to fill in a questionnaire and give their opinion on comprehensibility, clearness, brightness, and hinder. Video observations were made and vibration measurements were conducted while driving over the markings. The overview measurements reveal that the best way to measure the luminance of DRM is averaging over a certain width (15 cm in this study) because it enables comparison with laboratory measurements. On average, the contrast of DRM decreased with a factor 10 over the test period. When the DRM was switched off the contrasts varied between -0,2 and +0,2. The ratio between the luminance at day and at night, the dimming factor, ranges from 2 to 200. Measured from the emergency lane the luminance is on average 66% of the luminance measured from the right lane. In unfavourable conditions with a low sun elevation and wet pavement even the currently most bright DRM is not visible. The detail measurements show that the light bundles of the DRM have a width of about 20°. The luminous intensities of the DRM modules, straight ahead, at distances between 25 and 200 m, vary from 10 to 74 cd. The colour of 3 of 5 markings complies with the requirements for white as stated in the draft specifications (2000), one is too blue and one is too yellow. The luminous intensity of most old markings decreased to 5% en 80% of the intensities of new markings. The luminous intensity of one marking increased with 36%, caused by light scattering from large angles to the centre of the light bundle. Colour is not affected by ageing. Luminances calculated from the measured luminous intensities are a factor five higher than luminances measured on the road. Dirt, damage and differences in dimming settings probably cause this. From the road survey it appears that the interrupted marking is sufficiently recogniseking is sufficiently recognised. The recognition of the continuous marking was moderate. Switched-off markings are poorly perceived as switched-off markings, without any meaning. Road users are able to see differences in the width of the markings. Defective DRM, such as lamp failures, has a large influence on the appreciation. Too bright DRM are appraised as glaring. The different DRM types were appraised differently by subjects when the markings were over driven. Possibly the judgements are not only based on tangible but also on audible vibrations (sound). The video images showed no significant change in driving behaviour after the DRM was installed. Comparison of the objective luminance measurement and the subjective assessments reveal that in general a contrast of about 3 is appraised as clear and not disturbing. Contrasts higher than 10 are often judged as too bright. At nighttime, luminances of about 500 cd/m² are experienced as optimal. Because of the large spread in the data the values should be considered with some reserve. We gained more insight into the measurement of the luminance of DRM on the road and in the laboratory. We have also more insight into a number of important criteria concerning luminance, contrast, and comprehensibility of DRM. It appears that contrast, luminance, colour, dimming properties, angularity, width, distance between successive light points, and the flicker frequency are relevant aspects of DRM and should be addressed in the requirements. In order to get more reliable data for the establishment of specifications, more specific research is recommended to find the relationship between perceived and measured luminance and contrast in various light conditions in a controlled situation. Also the width and the comprehensibility of on and off switched DRM should be addressed in such research.training.(Author/publisher)
Samenvatting