To analyze China’s actual urbanization level, we iden- tified two statistical approaches: using the population living within the administrative boundaries ("administrative-based" method) and within the urba...To analyze China’s actual urbanization level, we iden- tified two statistical approaches: using the population living within the administrative boundaries ("administrative-based" method) and within the urbanized or built-up areas ("infrastructure-based" method) of cities and towns as urban population. To illustrate the two approaches and the associated problems, we used data for Tangshan City as a case study. The estimates on the "administrative-based" method were unreliable and the "infrastructurebased" method provided a 29.4% urbanization rate for Tangshan City in 2002, which is lower than the mean of 36.1% for China as a whole published after the fifth national census in 2000. Given the city’s geographic location, comprehensive urban construction and economic development indicators, its urbanization rate should be higher than the average level. Thus, our results indicate that the value of 36.1% was higher than the actual status as a result of poor statistical quality and overestimation of the floating population.展开更多
Existing optimization methodologies for intersection operations assumes a fixed geometric design, however the geometry and operational system should be simultaneously optimized to produce the best performance. Signali...Existing optimization methodologies for intersection operations assumes a fixed geometric design, however the geometry and operational system should be simultaneously optimized to produce the best performance. Signalized crosswalks are complex and critical pedestrian facilities. Their geometry and configuration directly affect the safety, cycle length and resulting delays for all users. As crosswalks become wider or they are placed further upstream, the cycle length will increase due to the all-red time requirement, which deteriorates the overall mobility levels of signalized intersections. In contrast, when crosswalk width decreases, the required minimum pedestrian crossing time increases due to the bi-directional pedestrian flow effects, which leads to longer cycle length. Furthermore, existing manuals and guidelines do not offer any specification for the required crosswalk width under various pedestrian demand conditions. This study aims to propose new criteria for designing crosswalk width at signalized intersections, which can optimize the performance from the viewpoint of vehicular traffic and pedestrians. The proposed methodology considers pedestrian demand and its characteristics （such as bi-directional flow effects）, vehicle demand and the geometric characteristics of the intersection The concept of optimized crosswalk width is proposed and demonstrated through a case study. Moreover, a comprehensive discussion regarding the merits and drawbacks of existing strategies on positioning crosswalks is presented. It was found that at signalized intersections, which are characterized by low pedestrian and high vehicle demands, crosswalk width of 2 meters is appropriate to minimize cycle length and resulting delays for all users including pedestrians.展开更多
基金supported by the National Basic Research Program of China (Grant no. 2005CB724206)the project of Master Plan of Yutian xian 2003–2020
文摘To analyze China’s actual urbanization level, we iden- tified two statistical approaches: using the population living within the administrative boundaries ("administrative-based" method) and within the urbanized or built-up areas ("infrastructure-based" method) of cities and towns as urban population. To illustrate the two approaches and the associated problems, we used data for Tangshan City as a case study. The estimates on the "administrative-based" method were unreliable and the "infrastructurebased" method provided a 29.4% urbanization rate for Tangshan City in 2002, which is lower than the mean of 36.1% for China as a whole published after the fifth national census in 2000. Given the city’s geographic location, comprehensive urban construction and economic development indicators, its urbanization rate should be higher than the average level. Thus, our results indicate that the value of 36.1% was higher than the actual status as a result of poor statistical quality and overestimation of the floating population.
文摘Existing optimization methodologies for intersection operations assumes a fixed geometric design, however the geometry and operational system should be simultaneously optimized to produce the best performance. Signalized crosswalks are complex and critical pedestrian facilities. Their geometry and configuration directly affect the safety, cycle length and resulting delays for all users. As crosswalks become wider or they are placed further upstream, the cycle length will increase due to the all-red time requirement, which deteriorates the overall mobility levels of signalized intersections. In contrast, when crosswalk width decreases, the required minimum pedestrian crossing time increases due to the bi-directional pedestrian flow effects, which leads to longer cycle length. Furthermore, existing manuals and guidelines do not offer any specification for the required crosswalk width under various pedestrian demand conditions. This study aims to propose new criteria for designing crosswalk width at signalized intersections, which can optimize the performance from the viewpoint of vehicular traffic and pedestrians. The proposed methodology considers pedestrian demand and its characteristics （such as bi-directional flow effects）, vehicle demand and the geometric characteristics of the intersection The concept of optimized crosswalk width is proposed and demonstrated through a case study. Moreover, a comprehensive discussion regarding the merits and drawbacks of existing strategies on positioning crosswalks is presented. It was found that at signalized intersections, which are characterized by low pedestrian and high vehicle demands, crosswalk width of 2 meters is appropriate to minimize cycle length and resulting delays for all users including pedestrians.
