Sensitivity analysis on stochastic equilibrium transportation networks using genetic algorithm

This study deals with the sensitivity analysis of an equilibrium transportation networks using genetic algorithm approach and uses the bi‐level iterative sensitivity algorithm. Therefore, integrated Genetic Algorithm‐TRANSYT and Path Flow Estimator (GATPFE) is developed for signalized road networks for various level of perceived travel time in order to test the sensitivity of perceived travel time error in an urban stochastic road networks. Level of information provided to drivers correspondingly affects the signal timing parameters and hence the Stochastic User Equilibrium (SUE) link flows. When the information on road system is increased, the road users try to avoid conflicting links. Therefore, the stochastic equilibrium assignment concept tends to be user equilibrium. The GATPFE is used to solve the bi‐level problem, where the Area Traffic Control (ATC) is the upper‐level and the SUE assignment is the lower‐level. The GATPFE is tested for six‐junction network taken from literature. The results show that the integrated GATPFE can be applied to carry out sensitivity analysis at the equilibrium network design problems for various level of information and it simultaneously optimize the signal timings (i.e. network common cycle time, signal stage and offsets between junctions).     

The development of a policy for road tax in Turkey, using a genetic algorithm approach for demand estimation

This study deals, first, with estimation of transport demand based on Genetic Algorithm (GA) approach, and then deals with the evaluation of the road tax system in Turkey. It proposes an alternative road tax policy. The total transport demand is estimated based on population, Gross Domestic Product per Capita (GDPPC), and vehicle-number. Three forms of the Genetic Algorithm Transport Demand Estimation for Tax Revenues (GATDETR) are developed, of which one is linear, and the second and third are exponential forms of the mathematical expressions. The best-fit GATDETR model in terms of total minimum relative average errors between observed and estimated values are selected for future demand estimation. The evaluation of the road tax system and policy proposal is made based on estimated demand. The Distance-Based-Taxation (DBT) system is proposed in order to control highway transport. With the DBT system, some road users may wish to use railway. Thus, we re-organize the railways in order to meet the demand, but this requires new fund. The DBT system may help to create to this fund. It may also help to develop fair-taxation for the road users. Results show that the GA can be used to model transport demand and hence income tax in future transports planning. This study also suggests that planning the taxation in highway transport may help to ease funding problem of railway system.     

Passing sight distance on two-lane highways: Review and revision

Several models have been developed to determine the minimum passing sight distance required for safe and efficient operation on two-lane highways. The American Association of State Highway and Transportation Officials has developed a model assuming that once the driver begins a pass, he/she has no opportunity but to complete it. This assumption is believed to result in exaggerated passing sight distance requirements. Considerably shorter passing sight distance values are presented in the Manual of Uniform Traffic Control Devices and are used as the marking standards in Canada and the U.S.A. More appropriate models have been developed considering the driver's opportunity to abort the pass, and are based on a critical sight distance which produces the same factor of safety whether the pass is completed or aborted. However, these models need to be revised to determine the passing sight distance requirements more accurately and to closely match field observations. In this paper, a revised model for determining the minimum required passing sight distance was developed, based on the concept of critical sight distance and considering the kinematic interaction between the passing, passed, and opposing vehicles. The results of the revised model were compared with field data and showed that the revised model simulates the passing manoeuvre better than the currently-available models which are either too conservative or too liberal. The results showed that the passing sight distance requirements recommended in the Manual of Uniform Traffic Control Devices are sufficient at low design speeds (50–60 k.p.h.) and for manoeuvres involving passenger cars only. For higher design speeds, the Manual of Uniform Traffic Control Devices standards are less than the passing sight distance required for safe and comfortable passes. The deficiency was found to increase with the increase in design speed, and reaches about 36% at a 120-k.p.h. design speed. Based on these results, major revisions to the current Manual of Uniform Traffic Control Devices marking standards are recommended.     

Grouper Culture: An Option for Grouper Management in Indonesia

Strong market demand, combined with the high price of live groupers for live food fish, aquarium fish, and grouper farming, has been enticing all participants in the live reef fish trade (LRFT) network in Asian countries to exploit more live groupers, resulting in an alarming situation regarding groupers in the wild. The current destructive fishing methods that are used to catch live groupers, the fishery's potential for overexploitation, and its impact to both fishers and consumers have raised many concerns among environmentalists, live grouper businesspeople, and the grouper fishers on the need to wisely manage the grouper resources in the wild. Introducing grouper culture looks promising as an option for grouper management.