PURPOSES : LED based Variable Message Signs(VMS) have been widely used to inform safety messages to the drivers in advance. Legibility Distance of VMS is the most important factor to provide the safety messages to drivers in timely and effective way. However, current National Standards on legibility distance design considers letter size only even there is a difficulty to read the signs at adverse weather conditions such as heavy fog. So, this study examined the legibility issue under fog by evaluating the legibility distance with two design factors such as letter size and luminance. METHODS : Two foggy weather conditions, intermediate and heavy fog, were simulated at real-road-scale Proving Ground. Legibility distance at daytime and nighttime was evaluated by test subjects. Subjects were asked to fill the legible distance on the test sheet and statistical significant was analysed at the lab. RESULTS : The legibility distance(LD) under fog was observed only 22 to 41% of LD observed under normal weather condition at daytime, and 26 to 45% at nighttime condition. Study results showed a consistent increase in LD with higher luminance even at same letter size and vice versa conditions, However, statically significant difference between groups was only revealed when both letter size and luminance level increased conditions. In order to apply the test results in terms of engineering benefits, LD results from significantly different groups was evaluated with relative to Stopping Sight Distance(SSD) within conceptual frame suggested in this study. CONCLUSIONS : From the study results, current National Standard on legibility distance design needs to consider letter size and luminance simultaneously to response the legibility issue in adverse weather conditions.

PURPOSES : This study aims to examine actual cases of providing detour information in accidental situations such as traffic accidents and road construction through a VMS installed on national highways in metropolitan areas with alternative routes, as well as cases of simultaneously providing travel time information on parallel paths such as national and regular highways. For each case, we analyzed whether the provision of VMS traffic information leads to route changes and substantial effects. METHODS : To analyze traffic changes on the main and detour roads based on the detour information provided on traffic accidents in actual cases, the traffic volume and speed on the accident day were compared with those on the same days and at the same time of the day (regular days) based on the VDS data of the main and detour roads. Cases providing more detour information on road construction were investigated by examining three time periods: one week from construction initiation and one week before and after the construction period (regular days). The traffic volume and speed on the main road were compared based on the VDS data, and those on the detour road were compared based on data made available by private entities. Regarding the cases of simultaneously providing drivers with comparative information on travel time over parallel sections of national and regular highways, traffic situation changes in highways were analyzed in the following special traffic control periods (New Year's Day, NY Day), during which congestion is expected due to heavy traffic: before and after the provision of comparative information for 2015 New Year's Day and 2016 NY Day. RESULTS : The detour rate related to route changes based on the detour information for traffic accidents was 35%. On the detour route, the traffic volume increases as traffic from the main road is absorbed. However, the average travel speeds did not differ significantly. When further detour information regarding a road construction project was provided, the detour rate from the main road was 21%. The travel speeds were similar, except on the first day of construction. Almost no changes were observed in the first section of the detour. The speed slightly decreased in the second section but did not significantly hinder the traffic flow. When comparative traffic time information on parallel routes (national highways and expressways) was provided, the traffic volume increased to some extent after the report was provided for every case. However, the data frequency rate in the 5-min unit, which was still under the congestion speed standard (40 km/h), decreased. This indicates that traffic congestion was significantly relieved. CONCLUSIONS : Previous studies on detour rates or route changes based on VMS traffic information have focused on VMS instruments on expressways. Although their estimates were based on simulated situations, this study used actual VMS installed on national highways. In addition, this study utilizes the existing case records of national highway ITS centers, covering traffic situation monitoring, measures for accidental situations, etc., in regular times or special traffic control periods, as well as statistical data, including ITS real-time traffic information. The analysis results of this study accurately represent situations on actual roads and can be utilized to analyze future ITS operation and installation project effects.

PURPOSES : Expressways experience chronic and recurring congestion, especially during weekends and holidays, because of the increased demands for leisure-related travel. The alternatives to solve chronic and recurring congestion may be three-fold: (1) physical expansion of expressway capacities, (2) road pricing, and (3) temporal and spatial distribution of traffic demands. Among these, the third alternative may be the most cost-effective method for the Korea Expressway Corporation (KEC) that can be achieved by using the existing ITS infrastructure. METHODS : KEC initiated a pilot study in which the traffic on congested expressways was managed by providing traffic condition information (i.e., travel times) of neighboring national highways for taking detours via variable message signs (VMS). This study aimed to estimate the detour rate, and the two pilot studies on Seohaean and Yeongdong expressways yielded many benefits. RESULTS: It was revealed that the total length of congestion segments decreased by 7.8 km, and the average travel speed increased by 5.3 km/h. CONCLUSIONS: Based on these findings, it was concluded that the propagation of detour information via VMSs during congestion hours can help reduce congestion on expressways and increase the benefits of the entire network.

PURPOSES: The purpose of this study is to estimate the impact of variable message signage (VMS) on traffic safety as a function of road curve radius using statistical methods. METHODS: In order to analyze the impact of VMS installations on traffic safety, travel speed, lateral distance, and geometric data relating to road curvature in each study area was acquired and analyzed for the impact of providing VMS information on driver performance and traffic safety using statistical methods including student t-test, Mann-Whitney test, and the Anderson-Darling test for estimating traffic safety hazard zone in each lane. RESULTS: As a result of analyzing driver performance characteristics before and after providing VMS information, it was determined that by providing VMS information, mean travel speed is deceased and vehicles are driven with increased precision, following the centerline in the first and second lanes. Also the results of analyzing traffic safety impacts of VMS indicate that traffic safety performance factors in the first lane of the Gapyeong section can, on average, increase in the left and right side of the lane by 19.22% and 68.98%, respectively, and in the case of the second lane, safety impacts, on average, can increase in both sides by 100%. For the Hongcheon section, traffic safety impacts in the first lane, on average, can increase along the left and right sides of the lane by 32.31% and 47.18%, and within the second lane, traffic safety can be increased along the left and right side of the lane by 10.97% and -0.01%, respectively. CONCLUSIONS: Based on the results of this study, the impact on traffic safety obtained by providing VMS information for road sections with smaller curve radii is greater than can be obtained for road sections with larger curve radii.

도로전광표지(Variable Message Signs, VMS)의 발광 소자는 발광다이오드(Light Emitting Diode, LED)를 광원으로 하고 있으며 램프 타입에서 칩 형태인 SMD(Surface-Mount Devices) 타입으로 변화하고 있는 추세이다. 이러한 LED 소자의 기술적 진보는 도로이용자에게 보다 밝고 선명한 광원으로 정보를 제공해 주기 때문에 과거보다 운전자의 시인성 및 판독성에 유리하다. 하지만 도로 이용자에게만 표출되어야 할 빛이 도로 이외의 영역(좌 우 및 상향)까지 비추어짐으로써 에너지가 낭비되는 결과로 이어지며, 간접적으로 생태계에까지 악영향을 초래할 수 있는 가능성이 높다. 따라서 본 연구에서는 도로 이외의 영역에 까지 비치는 도로전광표지의 빛을 가능한 도로 이용자에게만 표출할 수 있도록 광학 테스트를 통해 광원 표출 분포 및 에너지 효율성을 측정하여 최적의 조사각을 제시하여 에너지 절감 및 빛 공해 최소화(이른바 환경친화적 LED)를 궁극적인 목표로 설정하였다. 본 연구에서는 상 하향 24℃표출되었던 기존 도로전광표지의 LED 조사각을 운전자가 필요로 하는 판독 최소거리를 만족하는 조건에서 상향 0℃, 하향 11℃최적화하였고, 광학테스트를 통해 기존 도로전광표지 전력소모량 대비 약 36.1%가 절감되는 것으로 도출되었다. 궁극적으로 본 연구결과가 실제 현장에 설치된다면 현재 사용되고 있는 도로전광표지보다 표출 정보의 판독성이 향상되어 운전자의 정보 판독 거리를 늘려 안전운전에 도움을 줄 수 있으며 소비 전력을 줄여 국가 예산을 절감할 수 있을 것으로 기대한다.

본 연구는 지방부 고속도로 상에서 유출지점용 도로전광표지의 적정 설치지점을 도출하기 위하여, 차량시뮬레이터 실험 자료를 변수로 운전자가 도로전광표지의 교통정보를 판독한 후 고소고도로 유출시설로 우회가 가능한지 여부를 판단할 수 있는 판별식(Discriminant Model for VMS installation : DMV식)을 개발하는 것이다. 연구결과로는 (첫째), 차량시뮬레이터 실험을 통하여 도로전광표지 설치지점을 변경시키면서 운전자의 인적, 행태적 자료를 수집하고, 이를 근거로 도로전광표지 설치지점에 따라 우회 가능성을 판단할 수 있는 DMV식을 개발하였다. (둘째) 우회가능성은 도로전광표지 설치지점이 멀수록, 운전자경력이 많을수록 고속도로 운전경험이 많을수록, 차량속도가 낮을수록 높아지는 것으로 나타났으며, 우회가능성에 큰 영향을 미치는 변수는 도로전광표지 설치지점, 고속도로 경험, 운전경력, 차량속도 순으로 나타났다. (셋째), 개발된 DMV식의 예측력을 검증한 결과, 개별 운전자가 도로전광표지의 교통정보를 판독하고 이에 대응하여 우회가능성을 정확하게 예측하였다. (넷째) DMV식을 이용하여 설치지점에 대한 우회가능성의 민감도분석을 수행한 결과, 지방부 고속도로에서 운전자의 85%이상이 도로전광표지로부터 교통정보를 판독하고 유출지점으로 진입하기 위해서는 유출지점으로부터 최소한 3.2km의 이격거리가 필요한 것으로 분석되었다. 이는 피실험자가 20, 30대 운전자로 대표성에 한계가 있음을 감안하더라도 유출지점으로부터 건설교통부 지침에서 제시한 3.0Km이상의 이격거리가 필요하다는 것을 시사한다 하겠다.