Study On The Time Decision Of Reconstruction And Extension Freeway

With the socio-economy development, China has strengthened the development of transportation industry, especially has given the positive policy support to the construction of freeways, which represent the development level of modern transportation. Under the policy support, the freeways have realized continuous, speedy and orderly development. Until the end of 2005, the mileage of freeway opening to the traffic has reached approximately 41000 km. However, the adaptation of transportation to economy development is a sustaining and dynamic process. With the economy development, the original adaptation is interrupted by the increasing traffic. It is no exception for the freeways development, which presents a state from adaptation to no adaptation and to adaptation to the socio-economy development. With the rapid growth of the traffic volume and the advance of the freeway's function and position, the early constructed freeways appear traffic congestion, which has influence on road service level and traffic safety. But if construct a new freeway, it will invest more, take more time, take up more land resource and so on. So it inclines to reconstruction and extension project on the foundation of the original freeway.The decision on the reconstruction and extension time of freeway is an important macroscopical decision-making matter in the construction of transportation system. If the time lags behind, the highway traffic capacity will be insufficient and its service level descends, affecting the traffic safety and the economic growth; If the time advances excessively, there will be insufficient traffic volume and the utilization of traffic capacity will be insufficient, bringing about resource being extravagant. Both of the above situations should be avoided. Aiming at the optimum time of the reconstruction and extension time of freeway, the paper studies on it from the perspectives of the change trend of the highway service level and economic benefit of the reconstruction and extension project, and establishes the time decision-making of the reconstruction and extension project models respectively. Firstly, the paper applies the estimate technology of the freeway's entrance and exit OD matrix to predict the traffic volume of the sections in the original freeway. On basis of this, the paper calculates and analyzes the change trend of service level of the original freeway, establishes the trigger point mechanism model to determine the reconstruction and extension time based on the future highway service level; Secondly, according to the differences between the reconstruction and extension freeway and the new construction one in the economic evaluation and the economic property of freeway, this paper selects the gross methods in the economic evaluation. On basis of this, this paper establishes the econometrics model to determine the reconstruction and extension time based on the economic benefit. Finally, combining with the reconstruction and extension projects, the paper offers the demonstrations based on the above two models, looking forward to providing a reference for the reconstruction and extension projects to make correct decision and choose proper reconstruction and extension time.