A continuous network design model in stochastic user equilibrium based on sensitivity analysis

The continuous network design problem (CNDP) is known to be difficult to solve due to the intrinsic properties of non‐convexity and nonlinearity. Such kinds of CNDP can be formulated as a bi‐level programme, in which the upper level represents the designer's decisions and the lower level the travellers' responses. Formulations of this kind can be classified as either Stackelberg approaches or Nash ones according to the relationship between the upper level and the lower level parts. This paper formulates the CNDP for road expansion based on Stackelberg game where leader and follower exist, and allows for variety of travellers' behaviour in choosing their routes. In order to solve the problem by the Stackelberg approach, we need a relation between link flows and design parameters. For this purpose, we use a logit route choice model, which provides this in an explicit closed‐form function. This model is applied to two example road networks to test and briefly compare the results between the Stackelberg and Nash approaches to explore the differences between them.     

Shipper's councils: role and responsibility—a western view

This paper first presents arguments for having public sector port authorities. They can deal, flexibly and permanently, with property rights within their own areas. They can plan and regulate port areas comprehensively. They can provide ‘public goods’. They can deal, in various ways, with externalities. They can promote efficiency, whether their own (if they operate as a comprehensive port) or that of the private sector (if they are largely landlords). For example, if their policy is to rely on the private sector to produce efficiency through competition then they can see to it that there actually is competition and not any kind of cartel or monopoly. Examples are cited where this last function has not been performed. The exception for single-user ports is noted.

Against them are the general disadvantages of public authorities (or bureaucracies)—though examples are cited where port authorities had very small staffs. The common instances of ‘market failure’ may thus be contrasted with those of ‘government failure’. Finally, a pragmatic approach is advocated, tailored to the needs and resources of the country in question. The increasing effect of the economies of scale in port technology, and its limitation on competition, is, however, noted and to be discussed in the next paper.     

Short sea shipping: a Canadian perspective

Short sea shipping has begun to receive attention from governments worldwide, as they seek to reduce traffic congestion and greenhouse gases. Despite a long coastline and its interest in international maritime affairs, the Canadian government had, until 2003, placed greater emphasis on resolving the issues of other transport modes. In July 2003, Canada and the United States signed a Memorandum of Cooperation on Sharing Short Sea Shipping Information and Experience. Subsequently, the federal government embarked on an assessment of short sea shipping through a series of workshops. This paper explores the key issues with respect to further development of short sea shipping from a Canadian perspective. It examines the critical limitations and impediments to further growth of short sea services in Canada and trans-border trade with the USA, and identifies a number of questions Canadian policymakers need to answer.     

A note on the interpretation of the dual variables in estimating traffic capacity at signal- controlled road junctions

The values of the dual variables in a constrained optimisation problem can be used to estimate the sensitivity of the optimal value of the objective function to changes in the constraints. Allsop (1972) used standard methods of linear programming to derive expressions for the sensitivity of the reserve capacity at a signal-controlled road junction to various changes in the traffic engineering constraints. That analysis used the assumption that the maximum reserve capacity would be achieved when the cycle time used is maximal. While this normally occurs, some junctions have come to light where a reduction in the cycle time increases the capacity. Allsop's analysis is extended here to account for this possibility.     

A least absolute deviation critical decision path analysis with transport applications

This paper introduces a method that simultaneously analyzes travel variables from stated preferences that are measured under each of several different assumptions. The method uses least absolute deviation estimators and linear programming solutions and is flexible enough to permit inclusion of constraints for ordinal data and latent variables. Travel behavior is characterized by different indicators such as travel time, waiting time, mode choice and departure time. Consideration of different response variables simultaneously as part of a stated preference model requires a reclassification of variables as either endogenous or exogenous. This concept was introduced by the author as structural conjoint analysis earlier. Each endogenous variable may be defined as nominal, ordinal or cardinal and may be either explicitly measured or latent. Current econometric and psychometric techniques cannot accommodate this variety of data. The procedure is essentially a two-stage least absolute deviation simultaneous equation regression. The estimation technique is well known as are the various hypothesis tests. In the method each relationship between endogenous and exogenous variables is formulated separately carefully incorporating assumptions about each type of data. Thus there are different formulations for endogenous variables that are nominal and latent, ordinal and explicit, ordinal and latent, cardinal and explicit and cardinal and latent. Formulations for nominal latent, ordinal explicit and cardinal explicit variables were tested with simulated data for three separate hypothetical problems. Each problem consisted of at least two different types of variables and the technique was found to be able to reproduce the simulation function coefficients in virtually all cases.     

A linear programming approach to conjoint measurment and trade-off analysis

There has been increasing attention placed on decomposition techniques such as conjoint measurement and trade-off analysis. Existing algorithms for both approaches use non-linear estimation techniques. In this paper, a linear integration rule is proposed along with a linear programming algorithm which is used to estimate part-utilities by minimizing the sum of the absolute deviations subject to monotonicity constraints. The algorithm was tested on simulated data and empirically. It was found that the algorithm performed well, especially when data are consistent with initial assumptions.     

Capacity at a signal-controlled junction where there is priority for buses

A discussion of the benefits of bus priority schemes shows the importance of providing adequate capacity for all streams of traffic. The analysis of capacity at a signal-controlled road junction is extended to cases where stages may be truncated or omitted in some cycles. The problem of finding signal settings which, when implemented with priority, emulate some which are known to provide a given level of capacity when implemented without priority is considered. Two commonly used rules to give priority by selective vehicle detection are analysed in detail and a third is considered briefly to illustrate the flexibility of the methods used. The range of conditions under which these priority methods can be implemented without causing any loss of capacity is quantified. If an additional rule is implemented to prevent priority from being granted too frequently, then this range covers most practical operating conditions. In cases outside this range, consequent losses of capacity can be estimated. A numerical example based upon a real bus priority experiment is provided.     

Canada and the Liner Code of Conduct: Consumerism and public policy

This paper focuses on the potential effects the UNCTAD Liner Code of Conduct's provisions for cargo reservation on consumers of shipping services, with special reference to Canada. It is clear that as more nations enact flag-discriminating legislation then fewer choices amongest distribution options will exist for the consumer. This will involve nations like Canada in a fundamental reassessment of their current shipping policy, since the rationale of 'free market' competition will no longer be valid: carrier and services options will be curtailed. In the light of this, Canada will be forced to examine the concepts of 'free trade' and 'private sector enterptise' and develope a considered response that protects the consumer interest.