An analysis of the commuter departure time decision

Transportation planners and transit operators alike have become increasingly aware of the need to diffuse the concentration of peak period travel in an effort to improve gasoline economy and reduce peak load requirements. An evaluation of the potential effectiveness of strategies directed to achieve this end requires an understanding of factors which affect commuter trip timing decisions. The research discussed in this article addresses this particular problem through the development and estimation of a commuter departure time (to work) choice model.A number of conclusions were drawn based on the departure time model results and related analyses. It was found that work schedule flexibility, mode, occupation, income, age, and transportation level of service all influence departure time choice. The uncertainty in work arrival time and the consequences of various work arrival times may also be determinants of commuter departure time choice.The estimated model represents improvements over previous work in that it more explicitly considers work arrival time uncertainty and travelers' perceived loss associated with varying work arrival times, and additional socio-demographic factors which can potentially affect departure time choice. Furthermore, the estimated model includes consideration of transit commuters, in addition to single occupant auto and carpool work travelers. The inclusion of transit commuters represents a particularly important contribution for policy analysis, since the model could potentially be used to study the effect of service and employment policies on transit system peak load requirements.     

Effects of Operational and Design Parameters on the Sequence of Locking of the Wheels of Tractor-Semitrailers

It is known that loss of directional stability during braking occurs in many road accidents involving tractor-semitrailers. To minimize the undesired directional response, the correct order of locking of the wheels is of importance and should receive greater attention. This paper examines the effects of operational and design parameters on the sequence of locking of the wheels of tractor-semitrailers. The way in which the correct locking sequence may be achieved is also discussed in detail.     

Perceived and actual costs of operating cars

The perception that drivers have of car operating costs is an important factor in determining modal split characteristics. Theoretical figures derived from discriminant analysis models suggest that drivers perceive only petrol costs, but this has not been cor roborated by detailed surveys. This report examines in detail perceived and actual journey to work petrol costs of a sample of London commuters. The perception is also examined of related factors, such as petrol consumption and distance, in an attempt to throw some light on the perception mechanism itself.     

The effect of the oil crisis on the growth in the ownership and use of cars

Since the oil crisis of 1973, a number of studies have been made in various countries of the effects of the rise in petrol prices on the level of traffic flow, but rather fewer have attempted to delineate the complex chain of reactions within the car market set off by this impulse. We attempt to do this, using data from the UK.Since 1966 during the prediction stage of the first London Transportation Study it became obvious that low income and high income households had different rates of growth of car ownership, mainly because low income households bought cheap, old cars which vary in quantity and price differently from expensive, new cars. The Greater London Council therefore sponsored a study of car prices by age and size, starting from 1957 annually, and since the oil crisis, evaluated monthly. This has enabled us to examine the strong change in trend that had occurred, with large cars depreciating 15% per annum more than the smallest. The quantities of cars of each size registered each month are available from national statistics and this enables us to say that the previous 1% per annum increase in car size was arrested, with new cars becoming substantially smaller.A model of the car market has been developed which relates on the one hand the price distribution of cars by age, and on the other hand the price. distribution of the stock of cars owned at each household income level. Via the expenditure on car purchase at each household income level and the distribution of the length of time between purchase and resale of cars, a fully dynamic model has been developed to relate expenditure flow and stock. This enables us to test the effect of different trends on the dynamic equilibrium in the car market.The implications of the two trends noted above on the prediction of future car ownership growth are discussed, with the standstill since the oil crisis attributed to petrol prices via the split in household expenditure between purchase and use.     

The vagrant ethic: Need for a sea-lane philosophy

Although considerable progress has recently been made in the evolution of marine traffic procedures in coastal and waterway areas, mariners are finding difficulty in coping with the diverse traffic schemes that have so far been devised. This paper is a plea for international and logical marine traffic management, so that ships can operate safely and efficiently within a framework of the proliferating offshore zonal legislation that we are now witnessing.     

Travel intensity in a city with a barrier

An analytical study is made of the determination of the travel intensity at an arbitrary point of a city with a straight line barrier. For a given origin and destination a trip is made by the shortest path not crossing the barrier or the city perimeter. The joint trip end distribution is arbitrary except for a continuity assumption.     

Stability Criteria for Automobile-Trailer Combinations

The characteristic equation for a simple automobile-trailer combination is analyzed, revealing the parameter groups which are important in determining the stability characteristics. Application of Routh's method results in separate criteria for oscillatory and non-oscillatory criteria which can be evaluated algebraically, and which can also be displayed graphically showing a region of stability on a two-dimensional plot. The stability region is bounded by limits of oscillatory and non-oscillatory stability, and the evaluation of a specific case corresponds to the location of a point relative to the boundaries.