The planning and construction of a large underpass crossing urban expressway in Shanghai: An exemplary solution to the traffic congestions at dead end roads

To alleviate the increasing pressure from traffic chaos and congestion at peak hours in urban areas, more and more city expressways are constructed to facilitate the transportation. However, due to lacking of integrated traffic planning, massive arterial roads are separated as so called "dead end roads" by the expressways, leading to the inconvenience of commuting, even a sever to the transportation of the local network. In order to solve the problem, this paper investigated the traffic characteristics of dead end roads and the effect of underground crossing project, then proposed an innovative method of construction of large underpass in Shanghai soft ground. The experiences learnt from this project can provide useful references for solutions of dead end roads as follows: (1) The existing of dead end roads has direct influences on the traffic congestions of local roadwork, it's necessary to take measures to solve the transportation problems induced by it. (2) Underground solution is effective for tackling the problems induced by dead end roads. The commuting time is shortened by 70% and more than 34% of the surficial traffic flow of auxiliary lanes are diverted into the underpass. (3) The underpass can improve traffic conditions of road intersection and adjacent arterial roads. Turning traffic flows at the intersection between Tianlin Road and Mid-Ring Road has a dramatic decline from 65% to 81% and the traffic saturation of adjacent arterial roads has a reduction of about 10%. (4) For the advantages of little impact on traffic and environment, the Roof-box jacking method with earth pressure balanced cutter head is recommended for shallow buried undercrossing project in urban intensive areas.