Abstract
Considering the importance of maintaining network performance at desired levels under uncertainty, network reliability, as a new approach to assessing the performance of degradable urban transportation networks, has become increasingly developed in two recent decades. In this paper, a method for optimizing resource allocation to meet the required levels of transportation network reliability is proposed. The worked out method consists of two stages: at stage one, a method for computing the reliability of network connectivity based on the reliability of computing arc performance with an assumption that capacities are random variables for each arc is presented. These random variables are assumed to be conformed to especial probability density functions which can be modified through investing to improve the performance reliability of the arcs. At stage two, a mixed integer nonlinear programming model is developed to optimize resource allocation in the network. Numerical results are also provided in a simple network to demonstrate the capability of the employed method.
Highlights
Economic issues of a city or region necessitate a transportation system to be e cient, safe and reliable to provide an accessible network for trip-makers
Note that the states of a link may be considered as different de nitions determined by the planner. As it will be seen, this paper presents a new approach for computing the states of arcs, whereby the performance reliability of an arc is de ned considering the probability density function of its capacity and especial v C ratio as the level of service (LOS)
As explained in the previous sections, this paper concerns with two aspects of network reliability evaluation – performance reliability analysis and resource allocating with respect to reliability optimization. e subjects of those parts dealt with reliability analysis are similar in some existing works, and for the sake of comparing the numerical results obtained from the proposed and other methods, we have examined a simple test network employed repeatedly in network reliability analysis, in the case of capacity reliability studies
Summary
Economic issues of a city or region necessitate a transportation system to be e cient, safe and reliable to provide an accessible network for trip-makers. The level of service (LOS) is the most common measure for assessing the performance of a road segment de ned based on the density of vehicles per mile per lane (Highway Capacity Manual 2000). On a large spatial scale, vehicle-miles travelled (VMT), vehicle-hours travelled (VHT) and total delay can be used to evaluate the performance of a segment or an entire freeway system (Chen et al 2003). When designing a network is considered under uncertain conditions, we can hardly use aforementioned performance measures; network performance reliability has to be evaluated. Erefore, in degradable networks dealing with uncertain conditions, it is necessary to employ such e ective methods that can consider uncertainty associated with their evaluation parameters An earthquake pertaining to its destructive power is a probabilistic event and we are not able to predict if it occurs and how much intensity it will have. erefore, in degradable networks dealing with uncertain conditions, it is necessary to employ such e ective methods that can consider uncertainty associated with their evaluation parameters
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