Search Results (4)

A scientific and logical tunnel entrance lighting environment is an important guarantee for the safety of drivers entering tunnels as well as an essential element for the sustainable development of the tunnel. At present, most of the highway tunnel entrance lighting environment focuses on the road surface luminance and does not consider the variation of correlated color temperatures (CCT) on the driver’s vision in the tunnel access zone. This study analyzes the temporal and spatial variation of the ambient CCT in the driver’s 20° field of view during the approach to the tunnel through field dynamic tests of existing tunnels in the Beijing area. As a result, the CCT received by the driver’s eyes when approaching the tunnel peaks at the midpoint of the tunnel access zone, after which it decreases slowly up to the tunnel portal. Moreover, a calculation model of the CCT outside the tunnel with the solar irradiance, the distance from the tunnel portal, and the CCT of tunnel interior lighting as the input parameters is established. The modeling methodology was validated in a new tunnel, and the calculation model’s average absolute error is within 5%, which could provide guidance for the selection of the tunnel interior lighting CCT and a basis for the design of intelligent control of sustainable lighting systems in tunnels. Full article

In response to the special feature of the east–west oriented road tunnel entrance being easily exposed to direct sunlight, a study was conducted on the glare phenomenon at the access zone for this type of tunnel and on the time-varying characteristics of the L₂₀(S) value outside the tunnel. First, the actual situation of luminance difference inside and outside the tunnel was considered. Field tests were carried out in a 20° field of view of the human eye within a stopping distance. Then, the environment paraments outside the tunnel were collected by combining the environment schematic method with the digital camera method. Finally, the differences and time-varying characteristics between the measured and recommended values of luminance outside the tunnel were analyzed. The PGSV daylight calculation model was used to analyze the glare effect in the 20° field of view of the human eye. The results indicate that the luminance L₂₀(S) outside the tunnel towards the east (west) generally shows a trend of first increasing and then decreasing, and reaches its maximum value in the morning (afternoon). The difference in the contribution ratio of luminance inside and outside the tunnel for this type shows an overall trend of first increasing and then decreasing, and the maximum difference appears in the morning (afternoon), reaching about 97% and 96% respectively. The time-varying characteristics of glare in the access zone of an east (west) oriented road tunnel are roughly consistent with the variation trend of the luminance L₂₀(S) outside the tunnel and exceed the intolerable glare limit. Due to direct sunlight, the luminance outside the tunnel is too high, resulting in an uncomfortable glare that the driver cannot tolerate, becoming more serious after rainfall, and which affects driving comfort and safety. Full article

As the design basis of the tunnel lighting system, tunnel access zone luminance (TAZL) directly affects the energy efficiency of the tunnel lighting system and the driving safety of drivers. Affected by the relative position of the sun, weather conditions and other factors, the TAZL dynamically changes over time, but the existing tunnel mostly uses a fixed luminance value for the design and operation of the tunnel lighting system, which lacks a simplified method to obtain the real-time luminance. In this study, the L₂₀(S) (the average luminance observed by the driver at 20° field of view) at the tunnel stopping sight distance is split, and the sky luminance is calculated by using the sky luminance model. While a segmented prediction model of the ground scenery luminance is established with the maximum sun height angle as the inflection point, the solar irradiance outside the tunnel is adopted as the input parameter. This new proposed L₂₀(S) evaluation model is verified within the error of 5.41%, which provides a convenient and accurate method for the real-time measurement of TAZL. Full article

Because of the absence of lighting calculation tools at the initial stage of tunnel design, the lighting systems are usually over-dimensioned, leading to over illumination and increased energy consumption. For this reason, a fine-tuning method for switching lighting stages according to the traffic weighted L20 luminance is proposed at no additional cost. The method was applied in a real –case scenario, where L20 luminance of the access zone at eleven (11) existing tunnels was calculated. The traffic weighted method of CR14380 was used in order to calculate the actual luminance levels for the entrance zone. The new transition zone, which decreases luminance curves, was produced and compared with the existing ones. Thus, a new switching control was proposed and programed for the Supervisory Control and Data Acquisition (SCADA) system of the tunnel. The signals of the corresponding eleven L20 meters for a period of eight days were used and the corresponding annual energy consumptions were calculated using the proposed switching program for each tunnel. The results were compared with a number of scenarios in which the existing lighting system was retrofitted with Lighting Emitting Diodes (LED) luminaires. In these scenarios, the new luminaire arrangement was based not only on the existing luminance demand value for the threshold zone, but also on the newly proposed one with two different control techniques (continuous dimming and 10% step dimming). The fine-tuning method for switching resulted in energy savings between 11% and 54% depending on the tunnel when the scenario of the existing installation at no extra cost was used. Energy savings, when LED luminaires were installed, varied between 57% (for the scenario with existing luminance demand value for the threshold zone and 10% step dimming) and 85% (for the scenario with the new calculated luminance demand and continuous dimming). Full article