PURPOSES : This study is to evaluate environmental improvement effects of underground road project, as a case study of ‘Seobu’underground expressway project in Korea. METHODS : The environmental improvement effects of underground road construction were classified into tree sector in this study – air quality, noise, and thermal environment. To evaluate these effects, this study collected and divided environment dataset into before, during, and after ‘Seobu’underground expressway construction, and compared the change of values with entire city. In addition, the quantification method of environmental improvement effects was suggested based on the literature review. RESULTS : The result of this study indicates that there exist significant improvement effects of urban environment after the construction of ‘Seobu’underground expressway. Specifically, the concentration of particulate matters (PM10) and daytime/nighttime noise, and land surface temperature (LST) were improved along the expressway. In addition, the overall environmental benefit of ‘Seobu’ underground expressway was estimated to 1.15 billion won per year. CONCLUSIONS : To promote systematic and consistent underground road project, it is required to establish legislative system for evalauting and supporting urban improvement effects.

PURPOSES : Arterial work zones, particularly at signalized intersections, have several characteristics and effects different from freeways. This paper presents three significant work zone effects on signalized intersections: (1) saturation headway change (saturation flow rate change), (2) green time (g/C ratio) change, and (3) progression speed degradation impacts on bandwidth performance. METHODS : Both saturation flow rate reduction and g/C reduction were selected as the work zone impact variables for a signalized intersection, while bandwidth capacity reduction was chosen to measure the impact of work zones on arterials. The authors established a statistical model and normalized g/C table to estimate saturation headways and the g/C ratio at signalized intersection work zones based on the work intensity, pavement condition, ledge presence, turn percentages from shared lanes, and number of closed exclusive turn lanes. In addition, the dynamic bandwidth capacity and bandwidth solution space change based on the progression speed were introduced in this study. RESULTS : A normalized g/C ratio distribution was developed to estimate both the non-work zone and work zone g/C ratios under different work zone configurations. The results of the estimated work zone capacity using the work zone saturation headway model and the g/C ratio distribution showed that the estimated capacity reduction ranged from 32.78%~2.93%. In addition, arterial dynamic bandwidth and its capacity were both critically influenced by the progression speed. CONCLUSIONS : The proposed model and method will help practitioners understand the factors that cause a decrease in the saturation flow rate and g/C and influence progression quality on the urban arterial street due to work zones. Moreover, the proposed model and method can guide the calibration of simulation tools to properly represent the resulting capacity effects of work zones on arterial streets.

1993년 수립된 국가기간간선도로망 계획(7×9)에 따라 추진되어온 우리나라의 국토간선망 건설은 국민 의 교통애로 해소와 경제성장 및 지역 균형 발전에 크게 기여하여 왔다. 그러나, 최근 들어 사회의 요구가 사회복지 등에 초점이 맞추어지면서 도로건설을 둘러싼 주위환경은 더욱 엄격한 경제적 타당성을 요구하 고 있다. 이러한 사회적 분위기에 따라 국토간선도로망이라 할지라도 과거와 같이 고규격 도로인 고속도 로 건설만으로는 소기의 성과를 달성하기 어려워지고 있으며, 다양한 사업추진 방안 마련이 필요하게 되 었다. 따라서, 본 연구에서는 지역주민의 요구사항을 반영하면서 기존 국도를 활용하여 국가기간망을 건 설함에 따른 효과를 분석하고자 하였다. 국토간선망 중 동서5축의 일부에 해당하는 증평~괴산 구간을 대상으로 고속도로 건설시와 기존 국도를 활용한 자동차 건설시의 공사비, 용지비, 부대비 등의 사업비를 비교하였으며, 지역주민 설문조사를 통해 지역주민이 요구하는 간선도로 수준에 대하여 조사하였다. 연구 결과, 고속도로 건설시 42.7km에 16,914 억원에 이르는 공사비는 자동차전용도로 건설을 통해 1,295억원으로 절감이 가능하였으며 지역주민들은 통행료가 없는 자동차전용도로 건설을 더욱 선호하고 있는 것으로 나타나 향후 국가기간망 건설시 교통수 요가 적은 오지 지역의 경우 기존 국도 활용을 적극적으로 검토하는 것이 필요할 것으로 판명되었다.

PURPOSES : This study aims to evaluate the road safety of the super-elevation transition section of a left turn curve and suggest the minimum longitudinal grade of a super-elevation transition section to be used before and after a left curved section. METHODS: We evaluated the road condition by means of the safety-criterion-evaluation method involving side friction factors, and then solve the problem by introducing the minimum longitudinal grade criterion based on conditions described in the hydraulics literature. RESULTS : It was calculated that when a road satisfies hydroplaning conditions, the difference between side friction assumed and side friction demanded is less than - 0.04. In this case, the safety criterion for the condition is unsatisfied. Conversely, when a road is in a normal state under either wet or dry conditions, it was calculated that the difference between side friction assumed and side friction demanded is more than 0.01. Thus, the safety criterion for this condition is found to be satisfied. After adjusting the minimum longitudinal grade applied to a super-elevation transition section, the hydroplaning condition can be eliminated and the safety criterion can be met for all sections. CONCLUSIONS : It is suggested that a minimum longitudinal grade should be provided on super-elevation transition sections in order to prevent hydroplaning.

PURPOSES: The purposes are to analyze the pedestrian accident severity and to develop the accident models by arterial road function. METHODS: To analyze the accident, count data and ordered logit models are utilized in this study. In pursuing the above, this study uses pedestrian accident data from 2007 to 2011 in Cheongju. RESULTS : The main results are as follows. First, daytime, Tue.Wed.Thu., over-speeding, male pedestrian over 65 old are selected as the independent variables to increase pedestrian accident severity. Second, as the accident models of main and minor arterial roads, the negative binomial models are developed, which are analyzed to be statistically significant. Third, such the main variables related to pedestrian accidents as traffic and pedestrian volume, road width, number of exit/entry are adopted in the models. Finally, Such the policy guidelines as the installation of pedestrian fence, speed hump and crosswalks with pedestrian refuge area, designated pedestrian zone, and others are suggested for accident reduction. CONCLUSIONS: This study analyzed the pedestrian accident severity, and developed the negative binomial accident models. The results of this study expected to give some implications to the pedestrian safety improvement in Cheongju.

PURPOSES : The purpose of this paper is to develop a methodology to estimate level of service of arterial including Exclusive Median Bus Lanes. METHODS : On 6 Exclusive Median Bus Lanes routes in Seoul, bus travel time and number of bus-stop per km were investigated. Also whether or not passing lane exists at bus-stop was checked. Based on the data from sites, bus travel time was estimated according to length of segment, number of bus-stop per km and whether or not passing lane exists at bus-stop. RESULTS : A bus travel time table was developed according to length of segment, number of bus-stop per km and whether or not passing lane exists at bus-stop. After bus travel speed and passenger car travel speed is estimated based on each travel time table and length of segment, two speeds are combined with weighted average speed using traffic volume of each lane group. Then weighted average speed is a measure of effectiveness of arterial including Exclusive Median Bus Lanes. CONCLUSIONS : It can be concluded that the proposed methodology can estimate level of service of arterial including Exclusive Median Bus Lanes considering the operation characteristics of Exclusive Median Bus Lanes.

PURPOSES : The intents of the study are to identify the accident factors and to demonstrate the potentials of tobit model as a tool to study the number of accidents on arterial roads segments. METHODS : This paper uses a tobit regression as a methodology to analyze the factors affecting the number of accidents. In pursuing the above goal, this study gives particular attentions to analyzing the data of 2,446 accidents (1,610 in major arterial roads and 836 in minor arterial roads) occurred on arterial roads in 2007 to 2010. RESULTS : First, 3 accident models which were classified by total arterial roads, major arterial roads and minor arterial roads, and were all statistically significant were developed. Second, the exclusive right-turn lane as common variable, and the number of accident, traffic volume, number of lanes, link length, rate of median, number of entrances, number of pedestrian crossings, number of curves, number of bus stops and exclusive left-turn as specific variables of the models were selected. Finally, the paired sample t-test could not be rejected the null hypotheses of three types of models. CONCLUSIONS : Using data from vehicle accidents on arterial roads, the estimation results show that many factors related to roadway geometrics and traffic characteristics significantly affect to the number of accidents.

이 연구는 청주시의 가로구간 교통사고를 다루고 있다. 연구의 목적은 가로구간의 기능별 사고모형을 개발하는 데 있다. 이를 위해서 이 연구는 전체 472개의 세부구간으로 분리된 주간선도로와 보조간선도로의 사고 자료를 이용하여 적합한 모형을 개발하는데 중점을 두고 있다. 연구의 주요 결과는 다음과 같다. 첫째, 주간선과 보조간선도로의 사고특성에 대한 t 검정은 두 도로의 사고건수와 EPDO에 차이가 있는 것으로 나타나 기능별 사고모형 개발이 적절한 것으로 분석된다. 둘째, 주간선도로의 EPDO와 사고건수는 모두 ZINB모형이 적합한 것으로 분석된다. 셋째, 보조간선도로 EPDO는 ZINB모형, 그리고 사고건수는 ZIP모형이 최적인 것으로 분석된다. 마지막으로 주간선도로 사고모형(ZINB)의 공통변수는 교통량과 굴곡점수, 보조간선도로의 EPDO모형(ZINB)과 사고건수모형(ZIP) 공통변수는 평균종단경사인 것으로 평가된다.

본 연구의 목적은 가로구간 사고특성을 분석하고 주 야간 사고모형을 개발하는데 있다. 이를 위해 청주시 가로구간 24개 도로를 연구대상으로 2007년 사고 자료를 이용한다. 연구의 주요결과는 다음과 같다. 첫째, 가로구간의 주간 사고건수가 야간 사고건수보다 많았지만, 사고율에서는 야간사고율이 높은 것으로 분석되었다. 둘째, 4개의 사고모형이 개발되었으며, 이들은 통계적으로 모두 유의한 것으로 분석되었다. 마지막으로, 모형에 채택된 독립변수를 활용하여 주 야간 사고모형의 차이가 비교 분석되었다.