PURPOSES: This study aimed to evaluate the appropriateness of safety with the standard for threshold zone luminance as specified in the Recommendation for Lighting of Traffic Tunnel, which has been widely adopted worldwide. METHODS: A driving test of the subject in a full-scale road tunnel was conducted. The adaptation luminance and threshold zone luminance, which should be known for the driver to perceive an object within stopping sight distance, were obtained. These values were compared with the adaptation luminance and threshold zone luminance obtained by the existing reduced model test and tunnel lighting standard that has served as a guideline for the current threshold zone luminance standard. RESULTS : According to this study, threshold zone luminance should be increased to at least 1.8 times the value proposed in the existing studies and to twice the domestic tunnel lighting standard (KS C 3703: 2014). CONCLUSIONS : The threshold zone luminance proposed in this study differs largely from that obtained from indoor tests and from the current tunnel lighting standard used worldwide; this difference may be attributed to the fact that the indoor tests did not incorporate driving workload, non-uniformity of luminance distribution in terms of sight, and factors that reduce the visibility of the driver, such as the light reflected into the driver’s eyes. Hence, it is necessary to further review the factors that reduce the visibility of drivers approaching tunnels in order to determine the rational tunnel threshold zone luminance.

PURPOSES : The purpose of this study is to suggest a basis for setting appropriate safety goals specifically related to the threshold zone luminance in a vehicular traffic tunnel. . METHODS: In the test, drivers were divided into two groups. One group consisted of all drivers (average drivers) group with an age ratio of drivers holding domestic driver's license and driver group by age to produce threshold zone luminance in the tunnel. The threshold zone luminance produced as a result was used to analyze how it affects the safety level of each driver group and provide a basis for setting an appropriate safety criterion that can be used to determine threshold zone luminance. We used test equipment, test conditions, and ananalysis of threshold zone luminance identical to that reported by ChoandJung(2014) but the values of adaptation luminance in our analys is were expanded to range from100 to10,000 cd/m2. RESULTS : Adaptation luminance and threshold zone luminance are found to be related by a quadratic function. The threshold zone luminance needed by older drivers to ensure a certain safety level is significantly higher than that for drivers of other age brackets when adaptation luminance increases. 56% of older drivers are at an increased risk of an accident at the same luminance for which the safety level of average drivers is 75%. The safety level that can be achieved for older drivers increases to above 60% when threshold zone luminance level is set with the goal of attaining a safety level of more than 85% for average drivers. The safety level that can be attained for average drivers is above 90% when the threshold zone luminance is high enough to ensure over 75% in the safety level of older drivers. Results of this study are applicable to highways and others whose designed speed is 100 km/h. CONCLUSIONS : Threshold zone luminance determined on the basis of drivers having average visual ability is of limited value as a performance standard for ensuring the safety of older drivers. Hence, safety level for older drivers should be considered separately from safety levels for drivers with an average ability to avoid risk. Upward adjustment of older drivers' safety level in the process of determining appropriate threshold zone luminance in a vehicular traffic tunnel may bring both tangible and intangible benefit as a result of reducing accidents. However, there is an associated dollar cost arising from installing and operating lights. As a result, the economic impact of these trade-offs should also be considered.

도로 터널은 주간에도 조명이 필요한 구간이며, 특히 비교적 밝은 야외 환경과 접한 터널 경계부는 시각환 경의 복잡함을 고려 시 조명 설계에 특히 주의를 기울여야 한다. 터널 경계부는 터널 입구, 혹은 태양에 의한 입구 그림자 선으로부터 터널 안쪽으로 정지거리만큼까지의 구역으로, 터널 경계부의 조명은 설계속도로 주 행 중인 운전자가 터널 입구 경계로부터 정지거리만큼 떨어진 위치에서부터 터널 입구 경계에 도달할 때까지 지속적으로 터널 경계부의 장해물을 확인할 수 있도록 휘도 수준이 확보되어야 한다. 따라서 터널 경계부의 휘도는 운전자의 시각적인 특성과 더불어 설계속도 및 이에 상응하는 정지거리에 의해 영향을 받는다. 조원범, 정준화(2014)는 설계속도 100km/h인 도로를 대상으로 터널로 접근하는 운전자의 시야를 축소하 여 묘사한 조명 시뮬레이터를 활용하여 터널로 접근하는 운전자 시야 내 휘도분포를 묘사하기 위한 시나리 오를 구성하고, 피험자 21명 대상 실험을 수행하여 정지거리에서 터널 입구 경계에 위치한 장해물을 발견하 기 위해 필요한 경계부 휘도를 안전율별로 산정하였다. 안전율은 특정 순응 휘도와 경계부 휘도 조건에서 장해물을 확인할 수 있는 운전자의 비율 또는 특정 운전자가 장해물을 확인할 수 있는 확률을 의미한다. 본 연구는 설계속도에 따른 터널 경계부 휘도의 변화를 비교하기 위해 설계속도 80km/h인 도로를 대상으로 피험자 19명을 대상으로 터널 경계부 휘도 도출을 위한 실험을 수행하였으며, 이 결과를 조원범, 정준화 (2014)의 연구에서 도출한 설계속도 100km/h인 도로의 경계부 휘도 도출 결과와 비교하였다. 본 연구는 조 원범, 정준화(2014)와 동일한 실험조건을 적용하였으며, 단, 조명 시뮬레이터는 연구대상 도로의 설계속도 80km/h에 상응하는 최소 정지거리 110m에 맞춰 수정․활용하였다. 본 연구와 조원범, 정준화(2014)의 비교 결과는 표 1 및 그림 1과 같다. 설계속도 80km/h 대비 설계속도 100km/h 도로의 필요 경계부 휘도의 비율(이하 ʻ경계부 휘도비ʼ)은 안전율 75%의 경우 1.3~3.0, 안전율 50%의 경우 1.3~2.8에 분포하며, 순응휘도가 증가할수록 경계부 휘도비는 감소하는 것으로 분석되었다. 경 계부 휘도비는 80km/h 도로에서 필요한 특정 안전율을 확보하기 위해 필요한 경계부 휘도와 비교하였을 때, 동일한 안전율을 확보하기 위한 필요한 100km/h 도로의 경계부 휘도의 비율이다.

PURPOSES : This study has been performed with the objective to determine threshold zone luminance of adaptation luminance by target safety level in a vehicular traffic tunnel with design speed set at 100km/h . METHODS: The study made a miniature capable of portraying changes in luminance distribution within 2×10。conical field of view of the driver approaching to the tunnel for the test. Test conditions were set based on justifications for CIE 88-1990's threshold zone luminance used as a reference by domestic tunnel light standards (KS C 3703 : 2010). Luminance contrast of object background and object is 23%, object presentation duration is 0.5 seconds, and size of the object background is 7.3×11.5m2 RESULTS: Threshold zone luminance was set within adaptation luminance of 100~3,000cd/m2. Adaptation luminance and threshold zone luminance based on 50%, 75% and 90% target safety level all showed a relatively high linear relationship. According to findings in the study, it is not appropriate to specify the relationship between adaptation luminance and threshold zone luminance as luminance ratio. Rather, direct utilization of the linear relationship gained from the study findings appears to be the better solution. CONCLUSIONS : Findings of this study may be used to determine operation of threshold zone luminance based on target safety level. However, a proper verification and validity of test results are required. Furthermore, a study to determine proper threshold zone luminance level considering target safety level reviewed in this study and various decision-making factors such as economic conditions in Korea and energyrelated policies should be carried out in addition. Additional tests on adaptation luminance greater than 3,000cd/m2 will be performed, through which application scope of the test findings will be broadened.