현재 일본 등 외국에서는 특별히 금지된 장소 이외에는 차량 운전자가 “보행자나 다른 차량의 정상적인 교통을 방해할 우려가 없다고 판단하 는 경우”도로의 중앙을 넘어 우회전·좌회전 또는 회전(유턴)할 수 있 도록 되어있다. 그러나 한국에서는 1984년 당시,“교통안전”을 확보하기 위해 좌회전은 원칙적으로 교통 신호에 따라서만 가능하도록 하고, 원활한“교통소통”을 도모하기 위해 필요한 경우에는 관할 지방경찰청장이 특별히 허용한 장소 에서만 제한적으로 좌회전을 허용하는 방식의‘비보호 좌회전’이라는 독특 한 제도를 도입하였다. 원래‘비보호’란 법의 보호를 받지 못한다는 의미이며, ‘비보호 좌회 전’은 도로의 중앙을 넘어 반대방면으로 진입하는 운전 행위이기 때문에 매우 위험하다. 따라서 종래에는 도로교통법령에‘비보호 좌회전’하다가 교통 사고가 발생하면 좌회전 차량 운전자에게“신호위반”의 책임을 지고 무거운 처벌을 받도록 규정함으로써 평상시 경각심을 가지고 조심스럽게 운전을 하도록 유도하고 있었다. 그런데 2008년경부터 경찰청은‘비보호 좌회전’과‘유턴’확대,‘비보호 겸용 좌회전’ 신설 등 주로“교통소통”위주의 시책을 적극 추진하였다. 그 과정에서“적신호시, 좌회전시 등”기존의 보조표지를 제거한‘유턴’허 용 지점이 많아졌고, 그 결과 교통사고가 빈발하자, 일부 지역에서는 기존의 보조표지를 제거한‘유턴’허용지점에 현행법상 아무런 근거도 없는‘비보 호’라는 새로운 내용의 보조표지를 부착하는 등 현재‘비보호’는 관련법 규정과 실제 운용 실태 간에 상당한 괴리와 혼동이 발생하고 있는 실정이다. 그중에서도 특히 2010년 8월에는 ‘비보호 좌회전’하다가 교통사고를 야기 한 운전자에게는 “신호위반”의 무거운 책임을 지도록 했던 기존의 근거 규정 도 삭제되었다. 그 결과 녹색 신호에 정상 진행하다가 반대방향 도로에서 갑자기 튀어나온 비보호 차량과 충돌하는 사고를 당한 피해 운전자 입장에서 는 가해 운전자가 종합보험에 가입되어 있는 경우, 현행 「교통사고처리특례 법」상 불기소로 가볍게 처리됨으로써 그에 따른 불만이 크게 고조되고 있다. 따라서 이러한 문제를 해소하기 위해서는 교통사고 발생 시, 당사자 간 여러 가지 중대한 책임과 의무를 초래하게 되는 법상 ‘비보호’관련 규정을 다음과 같이 시급히 정비 ․ 보완해야 할 필요가 있다. 첫째, ‘비보호’및 ‘유턴’의 개념을 법 제2조에 신설하고, 관련 규정을 개정․보완해야 한다. 둘째, 이미 활용되고 있는 ‘비보호 유턴’을 현실화하고, 그 근거 규정을 신설하여야 한다. 셋째, ‘비보호 좌회전 및 유턴’통행하는 차마 운전자에 대한 책임성을 강화해야 한다. 넷째, ‘비보호 좌회전 및 유턴’의 법적근거와 사고 야기에 따른 처벌규 정을 신설해야 한다. 다섯째, ‘비보호 유턴’관련 안전표지 및 노면표시를 신설하고, 비보호 허용지점 전방에는 ‘예고 노면표시’를 설치 ․ 운용해야 한다.

PURPOSES :A complete signal system is not always the best solution for improving traffic operation efficiency at intersections. An alternative solution is to use a Protected Permitted Left Turn (PPLT) operation method. However, the PPLT method needs to be developed after a detailed study of driving tendencies, most notably the gap acceptance behavior, for successful implementation. In this study, the gap acceptance behavior was investigated under various variables and weather conditions, especially under rain, and the results were compared to the case of normal weather. The results of this study will be helpful in introducing the PPLT method, and are important considering the tendency of attempting unprotected left turns that is extremely common in Korean drivers.METHODS :Data was obtained by analyzing traffic footage at four intersections on a day when the precipitation was greater than 5 mm/h. The collected data was classified into seven variables for statistical analysis. Finally, we used logistic regression analysis to develop a probability distribution model.RESULTS :Gap, traffic volume, and the number of conflicting lanes were factors affecting the gap acceptance behavior of unprotected left turns under rainy conditions.CONCLUSIONS :The probability of attempting unprotected left turns is higher for larger gaps. On the other hand, the probability of attempting unprotected left turns decreases with an increase in the traffic volume. Finally, an increase in the number of conflict lanes leads to a decrease in the probability of attempting unprotected left turns.

PURPOSES : Permitted left turn is a turning maneuver in which a vehicle turns left using a gap between oncoming vehicles, called gap acceptance, and it enables for more efficient traffic operation at intersections. In Korea, the permitted left turn has not been a common maneuver at signalized or un-signalized intersections. However, many experts and the Police Agency tried to apply this effective turning maneuver at intersections in Korea since 2010. Though the investigation of gap acceptance is significantly important in understanding a driver’s behavior at intersections, there have not been many studies about this topic, specifically a study to develop probability models of gap acceptance behavior. METHODS: In this study, the probability model of gap acceptance behavior for a permitted left turn was developed based on observational field studies. To develop the model, seven variables were analyzed including gap, waiting time, traffic volume, conflict-flow vehicle type, leftturning vehicle type, the number of lane, and time. RESULTS: In the final model, gap and left-turning vehicle type were found to be significant influencing factors. CONCLUSIONS: Through this model development, it was concluded that as the gap size increased, the probability of gap acceptance was higher. Moreover, when a left-turning vehicle was a passenger car, the probability of gap acceptance was higher than compared to large size buses or freight cars.

PURPOSES : This study evaluated the feasibility of implementing protected-permissive left-turn (PPLT) signals at three-leg signalized intersections. METHODS: A three-leg signalized intersection with permissive left-turn was first selected. A VISSIM simulation model was constructed using data collected from the test site. The VISSIM network was calibrated by adjusting related parameter values in order to minimize the difference between the simulated and surveyed critical gap. The calibrated network was validated by the number of waiting left-turning vehicles per cycle. Finally, the mobility and safety measures were extracted from simulation runs in which permissive, protected left turns as well as PPLTs were realized based on diverse traffic volume scenarios. RESULTS : The mobility-related measures of effectiveness (MOEs) of the case with PPLT outperformed the other two left-turn treatment scenarios. In particular, the average waiting time per cycle for the left-turn vehicles in the case with PPLT was reduced by 30 s. The safetyrelated MOEs of the case with PPLT were somewhat higher than those in the case with protected left-turns and much higher than those in the case with permissive left-turns. CONCLUSIONS : Based on the mobility- and safety-related MOEs generated from the VISSIM simulation runs, the use of PPLT seems to be feasible at three-leg signalized intersections where the left-turn is permissive and a pedestrian signal exists at the conflicting approach. However, in order to use the PPLT in earnest, it is necessary to revise the road traffic act, traffic signs, and related manuals.