Transport planning with multiple criteria: The analytic hierarchy process applications and progress review

Five examples of applications of the Analytic Hierarchy Process (AHP) are made to illustrate the different uses of this ratio scale multicriteria decision method in transportation. They include a commuter route selection hierarchy, a best mix of routes to Pittsburgh's new International Airport, a benefits/costs hierarchy to choose the best mode to cross a river, a planning hierarchy for a transport system and a simple dependence with feedback cycle to choose a car when criteria depend on the alternatives. For a better appreciation of the use and power of the method, the examples are followed by a resume of developments in research on the (AHP) in the last few years.     

Crosswind Sensitivity of Passenger Cars and the Influence of Chassis and Aerodynamic Properties on Driver Preferences

Results of vehicle crosswind research involving both full-scale driver-vehicle tests and associated analyses are presented. The paper focuses on experimental crosswind testing of several different vehicle configurations and a group of seven drivers. A test procedure, which utilized wind-generating fans arranged in alternating directions to provide a crosswind “gauntlet”, is introduced and described. Driver preferences for certain basic chassis and aerodynamic properties are demonstrated and linked to elementary system responses measured during the crosswind gauntlet tests. Based on these experimental findings and confirming analytical results, a two-stage vehicle design process is then recommended for predicting and analyzing the crosswind sensitivity of a particular vehicle or new design.     

Environmental changes in the western Black Sea related to anthropogenic and natural conditions

The Black Sea northwestern shelf (NWS) ecosystem has been subjected to the strongest anthropogenic pressure of the entire Black Sea as about 80% of the freshwater runoff is discharged there.This paper presents a review of the global environmental changes related mainly to increased eutrophication in the western Black Sea basin.A case study (CoMSBlack 92a cruise) attempts to highlight the interaction of some natural and anthropogenic factors responsible for specific chemical and biological features in the western Black Sea environment. The significance of processes located near the Danube river mouth, which, due to their relatively small space scale, have not been recognized before, is clarified. Hydrological processess of specific importance to the distribution and transformation of antropogenic inputs are river plume dynamics, coastal upwelling and mixing and downwelling over the shelf break and slope in this part of the basin. A layer of low hydrological variability (“conservative layer”) appears to be a natural feature of the area, hypothesized to precondition specific biological and chemical processes there.The results suggest that the interplay between the Danube anthropogenic nutrient load with the natural hydrological fronts and gradients provides opportunities for enhanced biological activity thus contributing to the global environmental changes in the Black Sea NWS.     

Link choice proportions from trip distribution and assignment models: An overview and comparison

A number of estimation procedures have been suggested for the situation where a prior estimate of an origin-destination matrix is to be updated on the basis of recently-acquired traffic counts. These procedures assume that both the link flows and the proportionate usage of each link made by each origin-destination flow (referred to collectively as the link choice proportions) are known. This paper examines the possibility and methods for estimating the link choice proportions. Three methods are presented: (1) using ad hoc iteration between trip distribution and traffic assignment; (2) combining trip distribution and assignment in one step; (3) solving a new optimization problem in which the path flows are directly considered as variables and its optimal solution is governed by a logit type formula. The algorithms, covergencies and computational efficiencies of these methods are investigated. Results of testing the three methods on example networks are discussed.     

Characteristics of Guided-Steering Railway Trucks

The dynamic characteristics of guided-steering railway trucks are described both in a general sense and in terms of a specific design. Stability margins and curving performance have been predicted and are compared for both conventional and steered vehicles. It is shown that guided-steering trucks exhibit modes of instability which, although surmountable by proper design, are not found in conventional trucks. In particular, a low conicity, divergent, leading truck instability is described together with a companion high conicity, divergent trailing truck instability. Curving and dynamic performance for steered vehicles is shown to have the potential of being far superior to that of comparable conventional vehicles. Factors influencing the design of steered rail vehicles are presented and discussed.     

Junction interactions and monotonicity in traffic assignment

We consider the traffic equilibrium problem when the travel demand is inelastic and stationary in time. Junction interactions, which abound in urban road networks, are permitted. We prove that the set of equilibria (solutions to the assignment problem) is convex when certain monotonicity and continuity conditions are statisfied at each junction.     

A Study of the Response of a Double Bottom Vehicle to Steering and Braking

The paper describes the development, operation and some of the results obtained from a simulation of the steering behaviour of the double bottom articulated vehicle, in particular the effects that arise when certain axles are locked.     

Structural change in anglo-continental Ro-Ro traffic, 1977-1987

Elementary and generalized specialization indexes are used to detect structural change and its processes in the Ro-Ro traffic between the United Kingdom and Continental Europe. Powered vehicles dominate British exports through Channel and Straits ports, whereas unaccompanied trailers have the lead for traffic through North Sea ports. A major structural change took place on the continental side, where both forms of traffic came to a new balance in the Belgian ports between 1977 and 1987 in an otherwise stable market share context.     

Tackling traffic congestion in Accra,Ghana: A road user's perspective

A fast emerging component of the urban transportation problem in cities of the Third World is the problem of traffic congestion. Rapid increases in car ownership coupled with poor land use planning, inadequate road space, lack of regulated parking systems, uneducated use of the road by pedestrians, and bad driving behavior of motorists have all combined to produce congestions comparable to those experienced in cities in the advanced parts of the world. Traffic management measures have been tried in some of the major cities such as road expansion and redistribution of land uses in city centers, but most have produced minimal results. It is recommended in this paper that city authorities adopt an integrated approach to congestion with emphasis on influencing the behavior of the road users.