Yang, Chao
(2013)
Highway asset management.
PhD thesis, University of Nottingham.
Abstract
The aim of this thesis is to provide a framework for a decision making system to operate a highway network, to evaluate the impacts of maintenance activities, and to allocate limited budgets and resources in the highway network. This integrated model is composed of a network level traffic flow model (NTFM), a pavement deterioration model, and an optimisation framework.
NTFM is applicable for both motorway and urban road networks. It forecasts the traffic flow rates during the day, queue propagation at junctions, and travel delays throughout the network. It uses sub-models associated with different road and junction types which typically comprise the highway. To cope with the two-way traffic flow in the network, an iterative algorithm is utilised to generate the evolution of dependent traffic flows and queues. By introducing a reduced flow rate on links of the network, the effects of strategies employed to carry out roadworks can be mimicked. In addition, a traffic rerouting strategy is proposed to model the driver behaviour, i.e. adjusting original journey plans to reduce journey time when traffic congestion occurs in the road network. A pavement age gain model was chosen as the pavement deterioration model, which is used to evaluate the current pavement condition and predict the rate of pavement deterioration during the planning period. It deploys pavement age gain as the pavement improvement indicator which is simple and easy to apply. Moreover, the deterministic pavement age gain model can be transformed to a probabilistic one, using the normal distribution to describe the stochastic nature of pavement deterioration.
A multi-objective and multi-constraint optimisation model was constructed to achieve the best pavement maintenance and rehabilitation (M&R) strategy at the network level. The improved non-dominated sorting genetic algorithm (NSGA-II) is applied to perform system optimisation. Furthermore, the traffic operations on worksites, i.e. lane closure options, start time of the maintenance, and traffic controls, are investigated so as to prevent, or at least to reduce, the congestion that resulted from maintenance and reconstruction works.
The case studies indicated that NTFM is capable of identifying the relationship between traffic flows in the network and capturing traffic phenomenon such as queue dynamics. The maintenance cost is reduced significantly using the developed optimisation framework. Also, the cost to the road users is minimised by varying the worksite arrangements. Consequently, the integrated decision making system provides highways agencies with the capability to better manage traffic and pavements in a highway network.
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