PURPOSES : The purpose of this study was to quantitatively evaluate the variability of LiDAR performance indicators, such as intensity and Number of Point Cloud(NPC), according to various environmental factors and material characteristics. METHODS : To consider the material characteristics of road safety facilities, various materials (Reference Material(RM), reflective sheet, matte sheet, granite, plastic, and rubber) were used in a darkroom, and the performance indicators of LiDAR were repeatedly measured in terms of changes in the measurement distance, rainfall, and angle of observation. RESULTS : In the case of standard reflective materials, the intensity measurement value decreased as the measurement distance and rainfall increased. The NPC showed a tendency to decrease as the measurement distance increased, regardless of rainfall intensity. For materials with high-intensity values, it was found that rainfall intensity and color had negligible effect on the change in intensity compared with the measurement distance. However, for materials with low-intensity values, it was found that the measurement distance, rainfall intensity, and color all had a significant effect on the change in intensity. CONCLUSIONS : For materials with high-intensity values, it was found that rainfall and color had negligible effect on change in intensity compared with the measurement distance. However, for materials with low-intensity values, the measurement distance, rainfall, and color all had a significant effect on the change in intensity value.

PURPOSES : In this study, the factors affecting the severity of traffic accidents in highway tunnel sections were analyzed. The main lines of the highway and tunnel sections were compared, and factors affecting the severity of accidents were derived for each tunnel section, such as the tunnel access zone and tunnel inner zone. METHODS : An ordered probit model (OPM) was employed to estimate the factors affecting accident severity. The accident grade, which indicates the severity of highway traffic accidents, was set as the dependent variable. In addition, human, environmental, road condition, accident, and tunnel factors were collected and set as independent variables of the model. Marginal effects were examined to analyze how the derived influential factors affected the severity of each accident. RESULTS : As a result of the OPM analysis, accident factors were found to be influential in increasing the seriousness of the accident in all sections. Environmental factors, road conditions, and accident factors were identified as the main influential factors in the tunnel access zone. In contrast, accident and tunnel factors in the tunnel inner zone were found to be the influencing factors. In particular, it was found that serious accidents (A, B) occurred in all sections when a rollover accident occurred. CONCLUSIONS : This study confirmed that the influencing factors and the probability of accident occurrence differed between the tunnel access zone and inner zone. Most importantly, when the vehicle was overturned after the accident occurred, the results of the influencing factors were different. Therefore, the results can be used as a reference for establishing safety management strategies for tunnels or underground roads.

PURPOSES : The purpose of this study was to investigate directions for future smart city transportation policies and service development by evaluating road service satisfaction levels and predicting future service demand. METHODS : A nationwide survey was conducted in Korea to develop a transportation service evaluation system based on the functions and objects of transportation. The satisfaction level of road service was evaluated using an analytic hierarchy process (AHP), promising service sectors were identified using the revised importance-performance analysis (IPA) technique, and detailed service demands by sector were suggested. RESULTS : The most valuable service value felt by the people was "safety" (weight 0.4), and the overall satisfaction level was 68.9 points, slightly exceeding "normal." As a result of analyzing the promising service sectors by dividing them into urban and rural areas, "handicapped, elderly, and pedestrians" were important in both areas, and "road facility maintenance" was classified as an additional promising sector for rural areas. CONCLUSIONS : People demand that future smart city transportation policies and services should be "people" and "safety" centered. In addition, it is necessary to pay attention not only to the development of new services but also to the improvement of problems with existing services and policies.

PURPOSES : It is necessary to implement traffic-control strategies for underground roads. In this study, the application criteria for traffic control were developed to minimize actual traffic congestion on underground roads before it occurs. In particular, the traffic congestion judgement criteria and procedure (TJCAP) were developed. They can specifically classify the possibility of traffic congestion underground. METHODS : A microscopic traffic simulation model was used to analyze different scenarios. With the scenario simulation results, a hierarchical clustering analysis was applied to produce quantitative values from the TJCAP for each experimental network case. RESULTS : For network case (a), it was concluded that the possibility of traffic congestion on underground roads increases when the speed of the ground road connected to the main underground road and the connected ground road after the outflow of the ramp section is low. When the connected road is an interrupted facility after entering the underground roads, the red time is long, and when the section travel speed is 15 km/h, the possibility of traffic congestion underground is highest. A cluster analysis based on these results was performed using two techniques (elbow and silhouette) to verify the final classification. CONCLUSIONS : The TJCAP were designed to operate traffic flow with stricter criteria than traffic congestion management on ground roads. This reflects the difference in the driving environment between underground and above-ground roadways.

PURPOSES : In this study, we quantitatively prove the rubber necking phenomenon for highway traffic accidents and develop a calculation model based on the influencing factors. METHODS : Vehicle detector speed data in the opposite direction to the accident point were used based on the accident data on highways over the past three years, and a comparative verification was performed between nearby vehicle detector data to verify the reliability of the data. Accordingly, a binomial logistic model, ordinal probit regression model, and multilinear regression model were developed to compare the orientation. RESULTS : There was a difference in the influencing factors based on the dependent variable, and the day of the week, vehicle type, weather, longitudinal slope, and median height had an effect. Through a regression analysis, an influence coefficient was derived to calculate the driving speed deceleration value by rubbernecking. The results of the model analysis proved that the speed reduction caused by rubbernecking was more evident during the daytime than at night, during weekends compared to weekdays, and the speed reduction was more obvious for heavy vehicles compared to other types of vehicles. It can also be concluded that longer clearance time, higher accident severity, and higher traffic volume affect traffic delay. To verify the data and model equation, the mean prediction bias (MPB) and mean absolute deviation (MAD) were calculated for hundred cases randomly extracted from the collected accident data. These results were excellent. CONCLUSIONS : It can be developed into a human-engineered model that reflects various road/facility conditions, such as highways, other lanes, general roads, and roads without a median strip. This study is meaningful as a basic study on the quantitative effect of rubber necking.

PURPOSES : In this study, model-agnostic methods are applied for interpreting machine learning models, such as the feature global effect, the importance of a feature, the joint effects of features, and explaining individual predictions. METHODS : Model-agnostic global interpretation techniques, such as partial dependence plot (PDP), accumulated local effect (ALE), feature interaction (H-statistics), and permutation feature importance, were applied to describe the average behavior of a machine learning model. Moreover, local model-agnostic interpretation methods, individual conditional expectation curves (ICE), local surrogate models (LIME), and Shapley values were used to explain individual predictions. RESULTS : As global interpretations, PDP and ALE-Plot demonstrated the relationship between a feature and the prediction of a machine learning model, where the feature interaction estimated whether one feature depended on the other feature, and the permutation feature importance measured the importance of a feature. For local interpretations, ICE exhibited how changing a feature changes the interested instance’s prediction, LIME explained the relationship between a feature and the instance’s prediction by replacing the machine model with a locally interpretable model, and Shapley values presented how to fairly contribute to the instance’s prediction among the features. CONCLUSIONS : Model-agnostic methods contribute to understanding the general relationship between features and a prediction or debut a model from the global and/or local perspective, securing the reliability of the learning model.

2018년 음주운전차량에 윤창호 군이 사망하는 사고가 발생하고, 상습 음주운전에 대한 처벌을 강화하자는 국민들의 의견을 반영하여 도로교통 법 제148조의2 제1항이“제44조제1항 또는 제2항을 2회 이상 위반한 사람(자동차등 또는 노면전차를 운전한 사람으로 한정한다)은 2년 이상 5년 이하의 징역이나 1천만 원 이상 2천만 원 이하의 벌금에 처한다.”는 내용으로 일부개정이 있었다. 그런데 얼마 지나지 않아 2021. 11. 25. 헌법재판소에서 위 일부 개정된 도로교통법 중 제148조의2 제1항 중 “제44조 제1항을 2회 이상 위반한 사람”에 관한 부분이 헌법에 위반된 다는 위헌결정을 하였다. 헌법재판소는“제44조 제1항을 2회 이상 위 반”한 경우로 정하여 가중요건이 되는 과거 음주운전 금지규정 위반행위 와 처벌대상이 되는 재범 음주운전 금지규정 위반행위 사이에 아무런 시 간적 제한을 두지 않고, 죄질이 비교적 가벼운 유형의 재범 음주운전 행 위에 대해서까지 일률적으로 가중 처벌하도록 함으로써 형벌 본래의 기 능에 필요한 정도를 일탈하는 과도한 법정형을 규정한 것으로 책임과 형 벌 간의 비례원칙에 위반된다고 하였다. 그러나 음주운전의 행위태양 및 죄질의 경중에 차이가 있더라도 모두 반복된 음주운전 금지규정의 위반이라는 중요한 행위 반가치 지표적 측 면에서 다른 범죄들과 합리적으로 구별되는 동질의 범죄행위라고 볼 수 있으므로 개별적인 행위 태양을 고려하여 처벌규정을 더 세분화하지 않 았더라도 헌법이 요구하는 형벌체계에 어긋난다고 단정할 수 없다. 또한 비난가능성이 크지 않은 유형의 재범 음주운전의 경우를 위험한 반복적 음주운전행위와 동일하게 취급할 수 있다 하더라도 징역형 이외에 벌금 형이 있으므로 법관이 사실관계를 판단하여 양형을 통해 충분히 해결할 수 있는 부분이므로 이 사건 심판대상 조항의 가중처벌기준이 입법재량 을 현저히 일탈했다고 볼 수도 없다. 따라서 헌법재판소의 이 사건 위헌결정이 적절한지는 의문이다. 특히 상습 음주운전자에 대한 처벌조항이 강화되었음에도 여전히 도로교통법 (음주운전) 위반 발생건수가 감소되지 않고 있고, 국민들 사이에서 여전 히 음주운전 처벌강화에 대한 필요성이 언급되고 있으므로 이 사건 심판 대상조항을 위헌이라고 단정할 만한 국민들 사이의 법 감정에 변화도 존 재하다고 볼 수 없다. 이런 측면에서 헌법재판소가 이 사건 결정과 같은 위헌결정을 하고자 하였다면, 단순위헌결정이 아닌 법적 공백상태 및 형 벌규정의 위헌결정에 따른 소급적용으로 발생하는 재심 등의 여러 문제 를 고려하여 입법형성권을 존중하고 법적 안정성을 보장하기 위한 방편 으로서 헌법불합치 결정하는 것이 권력분립원칙에 더 부합한다고 할 것 이다.

도로협곡에서의 수목식재에 따른 보도 내 교통유발 대기오염도 변화를 살펴보기 위해 오픈소스 전산유체역학 코드 FDS(Fire Dynamics Simulator)를 사용하여 수목 투과지수, 식재 위치 및 유형에 따른 영향을 조사하였다. 광범위한 시뮬레이션을 통해 1) 관목층 만으로만 구성된 사례, 2) 관목층과 아교목층으로 구성된 사례 및 3) 관목층과 교목층으로 구성된 사례를 포함하는 400개의 시나리오 사례 중 399개 사례에 대해 유효한 데이터를 생성하였다. 분석결과, 보도 위에서 관찰되는 평균화된 정상상태 대기오염 농도는 식재유 형과는 무관하게 수목식재 후 약 10% 이상 감소하는 것으로 나타났다. 가장 큰 대기오염 감소효과는 관목층만으로 구성된 사례에서 관찰되었는데 대략 45%까지 감소하는 것으로 나타났다. 이러한 감소효과는 차선에서 인도로 대기오염물질을 직접 수송하는 선회류가 관목층에 의해 유리한 방향으로 변형되는 물리적 과정에 기초한다.

PURPOSES : The logistic roads for freight transport along to the new port of Busan have been suffered by the rapid weather changes including high temperature and torrential rain. As a result, the roads require annual repair, which have been distressed seriously by the heavy logistic and environmental loads. Therefore, we need to identify the cause of the road pavement distresses and find a proper design method to minimize the pavement distress in order to prohibit the problem aggravated. METHODS : The damaged conditions of the logistic roads were investigated on-site. In addition, applied pavement designs, real traffic volumes, and historical climatic information were intensively collected for this project. With the investigated and collected data Korean pavement design program (KPRP) was implemented to analyzed the causes of the damaged roads and conceive the pavement design draft optimized for the roads. RESULTS : According to the investigation and KPRP analysis, the traffic volume to transport freights impacts significantly the pavement distress, so that a higher PG grade binder type should be used, for which polymer modified asphalt (PMA) binders are recommended. Moreover, its pavement thickness should be increased to secure load bearing capacity, but thickening the pavement has been discouraged due to difficulties induced by the road-sectional change, especially road-height change. CONCLUSIONS : In conclusion, 5cm PMA overlay is suggested for the normal-scale maintenance, and 7cm PMA overlay for large-scale maintenance. Besides these, the application of Polymer-modified Stone Matrix Asphalt (PSMA) using PG76-22 binder would be the best preventive maintenance method, which has been well know as having higher fatigue resistant performance than general PMA. However, if we use PSMA, quality control should be very cautious since PSMA can be very susceptible premature distress if its production and construction are improperly proceeded.