In India, traffic flow on roads is highly mixed in nature with wide variations in the static and dynamic characteristics of vehicles. At unsignalized intersections, vehicles generally do not follow lane discipline and...In India, traffic flow on roads is highly mixed in nature with wide variations in the static and dynamic characteristics of vehicles. At unsignalized intersections, vehicles generally do not follow lane discipline and ignore the rules of priority. Drivers generally become more aggressive and tend to cross the uncontrolled intersections without considering the conflicting traffic. All these conditions cause a very complex traffic situation at unsignal- ized intersections which have a great impact on the capacity and performance of traffic intersections. A new method called additive conflict flow （ACF） method is suitable to determine the capacity of unsignalized inter- sections in non-lane-based mixed traffic conditions as prevailing in India. Occupation time is the key parameter for ACF method, which is defined as the time spent by a vehicle in the conflict area at the intersection. Data for this study were collected at two three-legged unsignalized intersections （one is uncontrolled and other one is semi- controlled） in Mangalore city, India using video-graphic technique during peak periods on three consecutive week days. The occupation time of vehicles at these intersections were studied and compared. The data on conflicting traffic volume and occupation time by each subject vehicle at the conflict area were extracted from the videos using image processing software. The subject vehicles were divided into three categories： two wheelers,cars, and auto-rickshaws. Mathematical relationships were developed to relate the occupation time of different cate- gories of vehicles with the conflicting flow of vehicles for various movements at both the intersections. It was found that occupation time increases with the increasing con- flicting traffic and observed to be higher at the uncontrolled intersection compared to the semicontrolled intersec- tion. The segregated turning movements and the presence of mini roundabout at the semicontrolled intersection reduces the conflicts of vehicular movements, which ulti- mately reduces the occupation time. The proposed methodology will be useful to determine the occupation time for various movements at unsignalized intersections. The models developed in the study can be used by practitioners and traffic engineers to estimate the capacity of unsignalized intersections in non-lane-based discipline and mixed traffic conditions.展开更多
运用Granier热消散式探针法,对鼎湖山自然保护区针阔叶混交林4种优势树种(马尾松、木荷、锥栗和广东润楠)的树干液流密度进行了长期连续观测,并同步监测林分的环境因子(光合有效辐射(PAR)、空气温度(T)、空气湿度(RH)、土壤含水量)。结...运用Granier热消散式探针法,对鼎湖山自然保护区针阔叶混交林4种优势树种(马尾松、木荷、锥栗和广东润楠)的树干液流密度进行了长期连续观测,并同步监测林分的环境因子(光合有效辐射(PAR)、空气温度(T)、空气湿度(RH)、土壤含水量)。结果表明:(1)4种优势树种的边材面积(As)与胸径(DBH)均存在显著相关关系(P<0.05);(2)各优势树种树干液流均呈现"昼高夜低"单峰曲线,且液流速率存在明显的季节性差异;(3)无论湿季还是干季,光合有效辐射(PAR)和水汽压亏缺(VPD)均为控制蒸腾的主要驱动因子;(4)4种优势树种湿季平均日蒸腾量高于干季,马尾松、木荷、锥栗、广东润楠湿季平均日蒸腾量分别为29.52、39.29、30.40、9.41 kg H2O/d,干季分别为20.91、24.84、24.26、8.43 kg H2O/d,干季和湿季的平均日蒸腾量(kg H2O/d)大小均为木荷>锥栗>马尾松>广东润楠,这种种间差异是由边材面积大小和树种本身的生物学特性共同决定的。展开更多
文摘In India, traffic flow on roads is highly mixed in nature with wide variations in the static and dynamic characteristics of vehicles. At unsignalized intersections, vehicles generally do not follow lane discipline and ignore the rules of priority. Drivers generally become more aggressive and tend to cross the uncontrolled intersections without considering the conflicting traffic. All these conditions cause a very complex traffic situation at unsignal- ized intersections which have a great impact on the capacity and performance of traffic intersections. A new method called additive conflict flow （ACF） method is suitable to determine the capacity of unsignalized inter- sections in non-lane-based mixed traffic conditions as prevailing in India. Occupation time is the key parameter for ACF method, which is defined as the time spent by a vehicle in the conflict area at the intersection. Data for this study were collected at two three-legged unsignalized intersections （one is uncontrolled and other one is semi- controlled） in Mangalore city, India using video-graphic technique during peak periods on three consecutive week days. The occupation time of vehicles at these intersections were studied and compared. The data on conflicting traffic volume and occupation time by each subject vehicle at the conflict area were extracted from the videos using image processing software. The subject vehicles were divided into three categories： two wheelers,cars, and auto-rickshaws. Mathematical relationships were developed to relate the occupation time of different cate- gories of vehicles with the conflicting flow of vehicles for various movements at both the intersections. It was found that occupation time increases with the increasing con- flicting traffic and observed to be higher at the uncontrolled intersection compared to the semicontrolled intersec- tion. The segregated turning movements and the presence of mini roundabout at the semicontrolled intersection reduces the conflicts of vehicular movements, which ulti- mately reduces the occupation time. The proposed methodology will be useful to determine the occupation time for various movements at unsignalized intersections. The models developed in the study can be used by practitioners and traffic engineers to estimate the capacity of unsignalized intersections in non-lane-based discipline and mixed traffic conditions.
文摘运用Granier热消散式探针法,对鼎湖山自然保护区针阔叶混交林4种优势树种(马尾松、木荷、锥栗和广东润楠)的树干液流密度进行了长期连续观测,并同步监测林分的环境因子(光合有效辐射(PAR)、空气温度(T)、空气湿度(RH)、土壤含水量)。结果表明:(1)4种优势树种的边材面积(As)与胸径(DBH)均存在显著相关关系(P<0.05);(2)各优势树种树干液流均呈现"昼高夜低"单峰曲线,且液流速率存在明显的季节性差异;(3)无论湿季还是干季,光合有效辐射(PAR)和水汽压亏缺(VPD)均为控制蒸腾的主要驱动因子;(4)4种优势树种湿季平均日蒸腾量高于干季,马尾松、木荷、锥栗、广东润楠湿季平均日蒸腾量分别为29.52、39.29、30.40、9.41 kg H2O/d,干季分别为20.91、24.84、24.26、8.43 kg H2O/d,干季和湿季的平均日蒸腾量(kg H2O/d)大小均为木荷>锥栗>马尾松>广东润楠,这种种间差异是由边材面积大小和树种本身的生物学特性共同决定的。
