Patterns of car usage and restraint modelling

Transport demand forecasting procedures have traditionally employed household based modal split models implicitly assuming a selection of mode for each trip based on relative generalised cost. A detailed examination of the trip patterns of a sample of household in West Yorkshire shows that in fact there is little discretionary choice of public transport; public transport trips in car owning households generally being explained in terms of the specific unavailability of the car for such trips. Two versions of a category analysis model for modal split are based on this observation and applied to household data for Glamorgan and Monmouthshire to show that such a procedure is workable and produces results comparing favourably with traditional approaches. The likely implications of three types of restraint policy are examined and it is concluded that the existing interdependence in trip patterns and modal choice within the household is of great significance in determining their effects. In particular it appears that positive attempts to increase vehicle occupancy at the peak are likely to be more favourable to public transport finances than the more negative policies to restrain use of the car for journey to work, or second car ownership.     

Estimating gravity model parameters: A simplified approach based on the odds ratio

Two computationally simple methods for calibrating the gravity model are presented in this paper. The use of each is demonstrated on several origin-destination trip tables, and the results compared with those obtained from the UTP system gravity model calibration procedure. Our methods, based on the odds ratio, perform at least as well as that of UTP system by several standard criteria.     

An Investigation of the Origins of Vibration of an Automobile Rear Axle

An investigation was carried out to determine the origins of vibration of an automobile rear axle with the object of establishing the significance of road-surface-induced vibratory inputs. This was achieved by measuring the vibratory acceleration of the rear axle of an automobile as it traverses straight sections of typically paved roads, at uniform speeds, then comparing the results with those obtained by laboratory simulation.

The investigation revealed significant levels of vertical, longitudinal and, to a much lesser extent, lateral vibrations. The main source of vertical vibrations is shown to be induced mainly by vertical displacements imposed by the road-surface irregularities on the vehicle tyres. The longitudinal and lateral components are shown to be induced mainly by the engine and the drive-line (including tyre/wheel assemblies) as well as due to coupling between the vertical, longitudinal and lateral motions of the rear axle imposed by the geometry of the rear axle suspension.     

Network equilibrium for congested multi‐mode networks with elastic demand

This paper proposes an elastic demand network equilibrium model for networks with transit and walking modes. In Hong Kong, the multi‐mode transit system services over 90% of the total journeys and the demand on it is continuously increasing. Transit and walking modes are related to each other as transit passengers have to walk to and from transit stops. In this paper, the multi‐mode elastic‐demand network equilibrium problem is formulated as a variational inequality problem where the combined mode and route choices are modeled in a hierarchical logit structures and the total travel demand for each origin‐destination pair is explicitly given by an elastic demand function. In addition, the capacity constraint for transit vehicles and the effects of bi‐directional flows on walkways are considered in the proposed model. All these congestion effects are taken into account for modeling the travel choices. A solution algorithm is developed to solve the multi‐mode elastic‐demand network equilibrium model. It is based on a Block Gauss‐Seidel decomposition approach coupled with the method of successive averages. A numerical example is used to illustrate the application of the proposed model and solution algorithm.     

An Approach to Determining Worst Case Platoon Behavior

This paper presents a method with which one can evaluate alternative platooning control strategies with respect to worst case behavior. The motivation is to provide platoon control designers with an objective means of evaluating robustness in the face of system uncertainties. The approach can be viewed as an extension of optimal control procedures and is applicable to complex, nonlinear systems. An arbitrary number of uncertain parameters, unmodeled components and inputs are allowed. The end result is a lower bound for the worst case platoon performance.     

Direct Covariance Analysis for the Calculation of Creepages and Creep-Forces for Various Bogies on Straight Track with Random Irregularities

In this paper creep-forces and creepages for an ICE express train coach and an electric locomotive BR 120 of the DB on straight track with random irregularities are investigated. The calculations are made with the multibody program MEDYNA using direct covariance analysis. One of the aims of this article is to emphasize the advantages of the direct covariance method (time domain) compared with the power spectral density method (frequency domain).     

Technical efficiency measurement and explanation of French urban transit companies

The performance of a sample of French urban transit companies is evaluated using a broad selection of nonparametric reference technologies for two specifications of the production process. In particular, the variable returns to scale Data Envelopment Analysis (DEA) models with either strong or weak disposability in both inputs and outputs, and the Free Disposal Hull (FDH) are applied. An extensive comparison of the resulting radial output efficiency measures yields the following major methodological conclusions. First, the location of the efficiency distributions differs substantially depending on the methodology and especially on the output specification considered. The latter differences vanish if the impact of outliers is eliminated. Second, convexity has a stronger influence on the efficient-inefficient dichotomy than allowing for congestion by means of a weakly disposable DEA model. For policy purposes, these efficiency distributions are explained using a Tobit model. The findings corroborate results reported elsewhere: the relevance of ownership, the use of risk-sharing incentives in contracting, the harmful impact of subsidies, etc. Furthermore, the network structure seems to account for some differences in performance. Finally, a novelty in the urban transit context is the indirect monitoring effect of the French earmarked transportation tax.