The primary objective of this work is to explore how drivers react to flashing green at signalized intersections. Through video taping and data procession based on photogrammetry, the operating speeds of vehicles befo...The primary objective of this work is to explore how drivers react to flashing green at signalized intersections. Through video taping and data procession based on photogrammetry, the operating speeds of vehicles before and after the moment when flashing green started was compared using paired-samples T-test. The critical distances between go and stop decisions was defined through cumulative percentage curve. The boundary of dilemma zone was determined by comparing stop distance and travel distance.Amber-running violation was analyzed on the basis of the travel time to the stop line. And finally, a logistic model for stop and go decisions was constructed. The results shows that the stopping ratios of the first vehicles of west-bound and east-bound approaches are 41.3% and 39.8%, respectively; the amber-light running violation ratios of two approaches are 31.6% and 25.4%, respectively;the operating speed growth ratios of first vehicles selecting to cross intersection after the moment when flashing green started are26.7% and 17.7%, respectively; and the critical distances are 48 m and 46 m, respectively, which are close to 44 m, the boundary of dilemma zone. The developed decision models demonstrate that the probability of go decision is higher when the distance from the stop line is shorter or operating speed is higher. This indicates that flashing green is an effective way to enhance intersection safety,but it should work together with a strict enforcement. In addition, traffic signs near critical distance and reasonable speed limitation are also beneficial to the safety of intersections.展开更多
Based on the VHF lightning locating system,a three-dimensional-space cell-gridded approach is used to extract the lighting channel and calculate the length of the channel.Through clustering of the located radiation so...Based on the VHF lightning locating system,a three-dimensional-space cell-gridded approach is used to extract the lighting channel and calculate the length of the channel.Through clustering of the located radiation sources and then extracting the lightning channel,it can accurately obtain the length of the channel.To validate the feasibility of the approach,a simulation experiment is designed,and it shows the length error is no more than 10%.The relationship between the NO production of per unit arc length and atmospheric pressure obtained in laboratory is applied to the NOX production of per unit flash length at different altitudes in this paper.The channel length and the NOX production of 11 negative cloud-to-ground flashes and 59 intracloud flashes in an isolated thunderstorm in the northeastern Qinghai-Tibet Plateau are calculated.The results show that the average channel lengths of per cloud-to-ground and intracloud flash are 28.9 and 22.3 km respectively;the average NOX productions of per cloud-to-ground and intracloud flash are 1.89×1025 and 0.42×1025 molecules,respectively.展开更多
基金Project(51208451)supported by the National Natural Science Foundation of ChinaProject(10KJB580004)supported by the Natural Science Foundation for Colleges and Universities of Jiangsu Province,ChinaProject supported by the New Century Talents Project of Yangzhou University,China
文摘The primary objective of this work is to explore how drivers react to flashing green at signalized intersections. Through video taping and data procession based on photogrammetry, the operating speeds of vehicles before and after the moment when flashing green started was compared using paired-samples T-test. The critical distances between go and stop decisions was defined through cumulative percentage curve. The boundary of dilemma zone was determined by comparing stop distance and travel distance.Amber-running violation was analyzed on the basis of the travel time to the stop line. And finally, a logistic model for stop and go decisions was constructed. The results shows that the stopping ratios of the first vehicles of west-bound and east-bound approaches are 41.3% and 39.8%, respectively; the amber-light running violation ratios of two approaches are 31.6% and 25.4%, respectively;the operating speed growth ratios of first vehicles selecting to cross intersection after the moment when flashing green started are26.7% and 17.7%, respectively; and the critical distances are 48 m and 46 m, respectively, which are close to 44 m, the boundary of dilemma zone. The developed decision models demonstrate that the probability of go decision is higher when the distance from the stop line is shorter or operating speed is higher. This indicates that flashing green is an effective way to enhance intersection safety,but it should work together with a strict enforcement. In addition, traffic signs near critical distance and reasonable speed limitation are also beneficial to the safety of intersections.
基金supported by the National Natural Science Foundation of Chi-na(Grant Nos.41075002,40775004,41030960)R&D Special Fund for Public Welfare Industry(Meteorology)(Grant No.GYHY201006005-03)
文摘Based on the VHF lightning locating system,a three-dimensional-space cell-gridded approach is used to extract the lighting channel and calculate the length of the channel.Through clustering of the located radiation sources and then extracting the lightning channel,it can accurately obtain the length of the channel.To validate the feasibility of the approach,a simulation experiment is designed,and it shows the length error is no more than 10%.The relationship between the NO production of per unit arc length and atmospheric pressure obtained in laboratory is applied to the NOX production of per unit flash length at different altitudes in this paper.The channel length and the NOX production of 11 negative cloud-to-ground flashes and 59 intracloud flashes in an isolated thunderstorm in the northeastern Qinghai-Tibet Plateau are calculated.The results show that the average channel lengths of per cloud-to-ground and intracloud flash are 28.9 and 22.3 km respectively;the average NOX productions of per cloud-to-ground and intracloud flash are 1.89×1025 and 0.42×1025 molecules,respectively.
