1,720,964 research outputs found
Estimating the value of travel time and of travel time reliability in road networks
Get PDFThis study proposes two network models which simultaneously estimate the value of travel time and of travel time reliability based on the risk-averse driver's route choice behavior. The first model is formulated as a utility maximization problem under monotonic and separable link travel times, whereas the second model is formulated as a utility maximization problem under non-monotonic and non-separable link travel times. The proposed models have the same structure as a user equilibrium CUE) traffic assignment problem with elastic demand. It is shown that the first model, which addresses independent stochastic capacity, is formulated as an optimization problem with a unique solution and is solved by using an algorithm for a UE traffic assignment problem with fixed demand. The second model, which addresses both stochastic Origin-Destination (O-D) flow and stochastic link capacity, is formulated as a nonlinear complementary problem. O-D demand functions formulated in the proposed models are derived from the utility maximization behavior of the driver in the network. Therefore, the network models proposed in this study are consistent with those of studies that address the value of travel time and of travel time reliability based on utility maximization behavior without considering the driver's route choice. Numerical experiments are carried out to demonstrate the models presented in this study
A model evaluating effect of disaster warning issuance conditions on "cry wolf syndrome" in the case of a landslide
Get PDFThis study proposes a model that clarifies how disaster warning issuance conditions affect "cry wolf' syndrome. The disaster assumed in this study is landslide caused by heavy rainfall. Local authorities that issue disaster warnings are thought to tend to avoid the situation where casualty occurs without the issuance to residents of a disaster warning. As a result, the issuance conditions may be relaxed. Under this circumstance, however, the residents are thought to tend to ignore disaster warnings, since such warnings are inaccurate. Thus may emerge the "cry wolf' syndrome. In this study, a simulation model that expresses the behaviors of the local authority and the residents has been developed. For the purpose of demonstrating the model, numerical experiments were then carried out. In the numerical experiments, the effects of optimal issuance conditions for disaster warnings on the cost incurred by the resident were evaluated by using assumed parameters for the model
Travel Time Reliability Estimation Model Using Observed Link Flows in a Road Network
Get PDFThis article formulates a model that calculates travel time reliability in a road network. The sources of uncertainty addressed by the model are traffic capacity and travel demand. Because travel time reliability estimation problem, in general, is formulated as a path-based problem, path enumeration can be required in advance. Thus, the path travel time reliability can depend on a path set enumerated in advance. For the purpose of determining the unique travel time reliability, a model that estimates stochastic path flows by using observed link flows is then presented. This method does not require predefined path set. However, this method is similar to the standard maximum likelihood (ML) estimation method, the method presented in this study is easier to be solved because the number of unknown parameters is much smaller than that of the standard ML estimation method. Numerical experiments using two networks are carried out to demonstrate the model presented in this article
A model evaluating effect of disaster warning issuance conditions on "cry wolf syndrome" in the case of a landslide
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A method for structuring stochastic travel time by using risk premiums of stochastic link flow
Get PDFThis study proposes a method for structuring stochastic link travel times in a road network with stochastic traffic demands. In our proposed method, the uncertainty of travel time is evaluated by link-flow-based indices. The mean link travel time is represented by using both its mean link flow and the corresponding risk premium of the stochastic link flow. The risk premium is defined by a concept of certainty equivalent derived from the relationship between a stochastic link flow and a link cost function. By expanding the concept of risk premium, a calculation method of link travel time covariance is proposed. Our proposed method defines bi-variate risk premiums, by which the mean of the product of two stochastic link travel times can be calculated. As a numerical calculation, we demonstrate our proposed method in a test network. Finally, we conclude and show future directions for evaluating real road networks
A numerical solution method for the fractional moment problem within engineering
No full textIn the field of engineering, the fractional moments of random variables play a crucial role and are widely utilized. They are applied in various areas such as structural reliability assessment and analysis, studying the response characteristics of random vibration systems, and optimizing signal processing and control systems. This study focuses on calculating the fractional moments of positive random variables encountered in engineering. By integrating Laplace transforms with fractional derivatives, both analytical and practical numerical solutions are derived. Furthermore, specific practical application methods are provided. This approach allows for the stable and highly accurate calculation of fractional moments based on the integer moments of random variables. Data experiments included in this study demonstrate the effectiveness of this method in solving fractional moment calculations in engineering. Compared to traditional methods, the proposed method offers significant advantages in stability and accuracy, which can further advance research in the engineering field that employs fractional moments
Economical welfare maximisation analysis: assessing the use of existing Park-and-Ride services
Get PDFThis paper assesses travellers' responses to the use of existing Park-and-Ride (P&R) services based on an economical welfare maximisation approach. Specifically, the paper presents a modelling framework to estimate consumer surplus and producer surplus (business profits) on the basis of modal choice probabilities. The paper draws on evidence from Stated Preference surveys conducted around two P&R sites in Sapporo, Japan, where P&R services occupy a modest market space. Overall, the results suggest that business profit increases when economical welfare is maximised, as a consequence of increased demand. It is also shown that P&R choice is not only influenced by parking fees, but also by the fares and other attributes of alternative transportation modes. Accordingly, the interactions of P&R with alternative transportation modes should be taken into consideration in any strategic transportation policies oriented towards motivating sustainable transport mode choices
Travel time reliability-based optimization problem for CAVs dedicated lanes
Get PDFThis paper proposed an optimization problem that determines the deployment pattern of dedicated lanes to connected autonomous vehicles (CAVs) considering the stochastic traffic demand and the stochastic traffic capacity. The difference between CAVs and regular human-piloted vehicles (RHVs) is driving behavior. The driving behavior of CAVs is expected to be more standardized than that of RHVs. Therefore, we assume that when the penetration ratio of CAVs increases in the lane flow, the mean lane capacity will increase, and the lane capacity variance will decrease. The mean and the variance of lane travel time decrease when the penetration ratio increases. Following this assumption, the difference in the stochastic properties between CAVs and RHVs is considered in a traffic assignment model. The traffic assignment model is formulated as a variational inequality problem. The network design problem with equilibrium constraints was solved by a simulated annealing algorithm in a test network
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