Offshore supply vessels: An emerging maritime industry

Over the last 13 years the sampled offshore workboat fleet has nearly doubled in size and vessels types have shifted to meet new work requirements. Maritime employment on these vessels may be equivalent to 8% of the world total for vessels over 100 get and is expected to grow. In the United States over the last 34 years the number of new jobs created in this activity approximates the number of jobs lost from the decline of us flag deepsea vessels. Vessels have been, and continue to be, administered primarily by us firms although a substantial broadening of international participation occured with the development of the North Sea and may also occur in the Far East. Expanding offshore development, a function of where remaining petroleum reserve lie, will require technological changes for success in deeper water and/or ice conditions.     

A probability analysis of some spatial interaction models

This paper derives several well-known spatial models in a framework based upon the laws of conditional probability analysis. In particular, it relates the structure of some existing models of trip distribution, elementary residential location and residential location with capacity constraints, to either the multinomial or hypergeometric probability distributions. The major changes from traditional methods for developing these models deal with the derivation and form of the objective function for each interaction model. This alternative analysis reaches a wider audience than that only familiar with entropy methods and leads to several improvements in generality. Further, when population constraints were imposed on residential location models, it was found that the model which developed naturally from the approach taken in the paper contained as a special case the model proposed by Dacey and Norcliffe and not the Wilson model.     

Using demand elasticities from disaggregate mode choice models

Three of the most highly regarded disaggregate mode split models incorporate very different estimates of the responsiveness, or elasticity, of mode choice to changes in auto travel times and costs. These differences appear to be due in part to the varying specifications used by the model, and particularly whether certain variables (such as a dummy variable for CBD destinations or automobile ownership) are included in addition to the more traditional variables (such as travel time, cost, and household income). More research is needed on the implications of the theory of traveler choices for model specification and the effect of alternative, but theoretically justifiable, specifications on elasticity estimates. Until this research reduces our uncertainty about the elasticity of demand, analysts evaluating transportation policies should assess the sensitivity of their results to the range of plausible elasticities or models.     

An actuary method for the estimation and comparison of urban bus transit cost of services

This paper presents a new cost allocation method developed for estimating the fully-allocated costs of the excess peak hour bus transit service provided by two public transit systems. The estimates were produced for the explicit purpose of carrying out a realistic comparison of these costs and the costs of the potential provision of the same service by private operators. The method utilizes the same service data for the analysis. The pragmatic estimation of the fully allocated costs of service by the public and private sectors enables a more accurate estimation of potential cost savings. Sensitivity analysis was also performed using the same costing procedure to determine the range of cost savings that are feasible in a competitive contract arrangement of private sector providers. The new method separates costs of the direct provision of service from other indirect costs and thus facilitates the identification of each cost item and its significance in comparative cost estimates.     

Household trip generation choice—Alternative empirical approaches

Trip generation models have generally received less attention than other aspects of travel decision making. This article presents some explorations into the structure of trip decisions for shopping, using data from weekly shopping diaries. The paper compares alternative formulations of the naturally-ordered choice model used by Sheffi (1979) to avoid the problems inherent in multinomial logit models. Firstly, imposing cross-alternative restrictions on some of the coefficient values is termed the constrained model. Secondly, when no such restrictions are imposed, the model decomposes into a sequence of binary models, and this is termed the unconstrained model, which can be used to test the validity of the restrictions. The variables used include both shopping expenditures and locational factors, both of which are found to play a key role in shopping travel decisions, as well as more conventional socio-economic variables. A clearer understanding of the role of car ownership in travel decisions is obtained.     

Economic policies and seaports: The diversity of port policies

This paper contrasts the economic policies adopted towards seaports by different countries in terms of their approaches to national, regional or local control. Various examples are presented and described, together with some of the difficulties that have been encountered. Examples are cited where national, regional and local governments have become involved, even though constitutional provisions appeared to present this. It is argued that national, regional and local governments all have interests in the efficiency of ports from various points of view; hence all should be involved. The arguments for and difficulties experienced in centralized planning and co-ordination are also discussed.

The variety of activities directly undertaken by port authorities is discussed, with the extreme positions labelled 'landlord' and 'comprehensive'. The remarkable variety of intermediate positions is also described. Whilst oversimplification is dangerous, the opportunities for expanding the private sector are analysed, even to the extent of wondering whether public sector port authorities are needed at all. This, therefore is the subject of the next paper.     

Monitoring urban spatial dynamics

As urban systems increase in size and diversity, the factors which influence spatial change increase in number and their interactions become more complex. Increasing emphasis is thus being placed by some governments and agencies on regular reviews of policies and programs, to ensure that they are consistent with and facilitate the evolving urban form. Consequently, the monitoring of urban transport and activity systems is of increasing importance, to aid the review processes. This paper considers the progress which has been made in and use of procedures for monitoring urban, transport-related spatial changes. The specification, estimation and presentation of appropriate indicators is briefly discussed. Experience with the use of spatial monitoring procedures on data for two Australian cities has revealed several possible implications for transport investment practice and the development of monitoring and modelling procedures. These are discussed and the paper then indicates the approach which is currently being taken at ARRB towards developing a monitoring system.