An examination of the determinants of day-to-day variability in individuals' urban travel behavior

Day-to-day variability in individuals' travel behavior (intrapersonal variability) has been recognized in conceptual discussions, yet the analysis and modeling of urban travel are typically based on a single day record of each individual's travel. This paper develops and examines hypotheses regarding the determinants of intrapersonal variability in urban travel behavior.Two general hypotheses are formulated to describe the effects of motivations for travel and related behavior and of travel and related constraints on intrapersonal variability in weekday urban travel behavior. Specific hypotheses concerning the effect of various sociodernographic characteristics on intrapersonal variability are derived from these general hypotheses. These specific hypotheses are tested empirically in the context of daily trip frequency using a five-day record of travel in Reading, England.The empirical results support the two general hypotheses. First, individuals who have fewer economic and role-related constraints have higher levels of intrapersonal variability in their daily trip frequency. Second, individuals who fulfil personal and household needs that do not require daily participation in out-of-home activities have higher levels of intrapersonal variability in their daily trip frequency.     

A note on using Davidson's function in equilibrium assignment

This paper describes the use of the Davidson congestion function in modelling network flows using equilibrium assignment. A modification to the function is given, which defines the function over all flows values, and consequently removes computational difficulties noted in earlier studies. The modification requires the inclusion of an additional model parameter, and the selection of a suitable value for this parameter is studied for two sets of data. The modified Davidson function is also compared to two alternative functions; a step-wise linear function and a quartic polynomial function, which have both been proposed as congestion functions. Comparisons are made between observed link volumes and the assigned volumes from these models. It is concluded that the modified Davidson function is useful for inclusion in an equilibrium assignment model, given its ability to reflect differences in network link type (e.g. capacity and speed) and environment through its parameters, the conceptual advantage of the function through its derivation from queueing theory, and the previous discovery of reliable methods for estimating its parameters. A value of about 0.8–0.9 is suggested for the parameter (μ, 0 < μ < 1) introduced in the modification.     

Comparative environmental impacts of different modes

While modern railway systems in general are considered to have comparatively low environmental impacts, high speed rail systems require special attention to ecological appraisal. Two case studies are presented - the new rail lines of the West German Federal Railways, and the European high speed rail project Paris-Brussels-Cologne/Amsterdam — which show that environmental compatibility can be costly and time-consuming. However, it would seem that the environment would not be a main issue for the proposed Amsterdam-Groningen-Hamburg connection if it primarily used existing rail lines.     

The state-of-the-art of “comprehensive” planning

Planning occurs as a part of governmental operations wherever decision-making happens. For US metropolitan areas, the locuses of decision-making are multiple, ranging in scale from very small jurisdictions up through the hierarchy to state and federal levels, and in function from general governments to many special-purpose agencies — transportation, health care, education, etc. Almost all might affect or be affected by urban transportation decisions and actions. Since no one of these units of government is comprehensive in authority and activity, there is no single, centralized planning operation that is truly comprehensive. Pluralistic planning is increasingly trying to foresee and to accommodate the interactions among the various levels and functions. Instead of fragmenting, with the fragments pulled apart and insulated, we need to move toward partitioning, not merely to delimit boundaries but also to identify interfaces. This movement is hampered by the differentials in the development of the state-of-the-art of the technical planning process now used by the several levels and functional units of government. This is most advanced, and most effective, for small, homogeneous suburban jurisdictions primarily concerned with guiding and controlling physical development; it is in disarray in central cities trying to cope with social and economic problems as well as with physical deterioration; at the metropolitan scale it is highly developed technically but not very influential. There is a trend toward a network of planning activities that recognizes and facilitates interrelationships and interactions, both vertically among functional boundaries and horizontally across geographical-scale distinctions — a trend toward the comprehensive —but we have a very long way to go.Paper prepared for the Highway Research Board Conference on Organization for Continuing Urban Transportation Planning.     

Wheel/Rail Contact: Geometrical Study*

Before trying to ascertain the precise nature of the Wheel-Rail contact (internal stresses and strains, wear and friction, security against a derailment, dynamic behaviour of the vehicle, etc.) the geometrical problem must necessarily be solved. That is, for each position of the wheelset (this is defined by 6 parameters, of which only 4 are independent) the two dependent parameters and the coordinates of the points of contact of each wheel, and rail must be obtained. A new method is proposed of obtaining the spatial position of a wheelset with reference to the rails, from the most general point of view.     

Some evidence of transit demand elasticities

This paper draws together empirical evidence from a variety of sources about the magnitudes of transit price elasticities and cross-elasticities. A number of different practical measures of demand elasticity are first defined and some expectations about magnitude are discussed. Evidence is then collated from the analysis of transit operating statistics, from experience in demonstration projects and from attempts to develop cross-sectional models of demand and modal choice.In general, all of the limited evidence available suggests that transit demand is inelastic with respect to money price. Typically, ridership is significantly more sensitive to changes in the level of service (particularly door-to-door journey time) than to changes in fare, although service elasticities also are usually numerically less than unity.In broad terms, short-run direct fare elasticities are characteristically observed to lie within the range of -0.1 to –0.7. A more precise value in a particular instance will depend on a variety of factors in ways which largely support a priori notions. Thus in very large cities, central city areas, at peak hours, and in other circumstances where the prices of alternative modes are high, transit fare elasticities are usually numerically at the lower end of the range.Estimates of cross-elasticities (representing the volumes of transit traffic diverted to other modes by transit price increases) are much harder to come by, and in fact only a few very uncertain estimates are presented here.This paper is a condensation of an Urban Institute Working Paper of the same title (WP 708-52, November 1971). Opinions expressed are those of the author and do not necessarily represent the views of The Urban Institute or its sponsors.     

Rail freight transportation: A review of recent optimization models for train routing and empty car distribution

This paper describes two types of rail transportation problems in detail. These are train routing and makeup, and empty car distribution problems. Some of the recent optimization models which address these problems are reviewed and the areas for potential improvements in rail transportation literature are identified. The type of interactions which exist between routing, makeup, and empty car distribution decisions are highlighted and potential areas for future research are identified.     

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.