Traffic assignment in a two-dimensional continuous representation of a traffic network with flow-dependent speeds

The work deals with the assignment of traffic to a two-dimensional continuous representation of a traffic network. An important aspect of the treatment is that the reciprocal of the speed on each road in the network is at all times a linear function of the flow on that road. This speed-flow relationship is generalized to two-dimensional space using travel intensities and taking account of road densities, so that there is direct dependence of speeds upon flows at all points regardless of their location. There is also dependence of flows upon speeds at all points because Wardrop's first assignment principle is adopted. That is, for a given O-D pair, journey times on all routes actually used are identical, and less than journey times on all other possible routes. This results in the identification for each O-D pair of an “assignment zone”, an area within which all trips between that O-D pair are made, and beyond which no such trips are made. For a single O-D pair the assignment zone is identified by ?_m, the maximum angular divergence of a path from the straight line between O and D. Paths are then assumed to be bilinear so that for a single O-D pair the assignment zone is a parallelogram. Journey times, speeds, lateral displacement and other related quantities are obtained as functions of the flow Q between O and D. The work is extended to three O-D pairs located at the extremities of an equilateral triangle and four O-D pairs located at the corners of a square. At low flows these two configurations are trivial extensions of the single O-D pair problem because assignment zones do not overlap. At higher flows account is taken of this tendency to overlapping, so that although they do not overlap they do touch, becoming kite-shaped. Origins and destinations are assumed to be at the periphery of small circles of arbitrary radius. The work is inelegant to the extent that it involves a numerical integration but it is possible that this might eventually be circumvented.     

回到1971的未来

战火纷飞的年代,汽车制造商们关心的是汽车的安全性能和楔形主题1971是动荡的一年。北爱尔兰动乱升级,多少无辜的平民被杀害;美国仍深陷越南战争的泥潭。第26届联合国大会以压倒性多数通过第258号决议,决定恢复中华人民共和国在联合国的一切合法权利。那时的苏联仍是西方阵营的头号敌人。     

回到1988年的未来

1988年的概念车是跟小家碧玉毫不沾边的风格o汽车产业在第二次爱之夏时为之疯狂。1988年,乔治·布什刚当选美国总统。而在底特律,凯迪拉克Voyage也在另一场备受关注的选举中脱颖而出,成为这场秀的明星。这辆轿车外观时髦.像