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On a car-following law
Translated abstracts B. PETIGNY: On a car-following law. Transpn Res. 2, 151-155. Two variations are proposed on a well-known car-following law, which treat the special case of return to uniform speed after a disturbance. According to the principles set forth, it appears (i) that oscillations with fixed or increasing amplitude practically never exist, (ii) a decreasing oscillation can, however, arise if the uniform speed reached after the perturbation is below a certain value which increases with increase in the following driver's sluggishness in perception and roughness in execution of driving maneuvers.
NELSON M. ISADA: Effects o f speed and camber on the ride behavior o f a rapid transit vehicle traversing a dynamic roadway. Transpn Res. 2, 157-169. This paper deals with the analysis, based upon solutions obtained by computer, of the effects of vehicle speed and roadway beam camber on the vertical ride behavior of a rapid transit vehicle. The roadway is considered to be a simply supported beam in dynamic flexure which possesses inertia and equivalent viscous damping, whereas the vehicle is simulated as a four-degree-of-freedom system. F o r the vehicle-roadway system considered, it is found that camber is beneficial at cruising speeds (30-50 m.p.h.) but it produces larger r.m.s. (root mean square) and maximum (magnitude) pitch displacements at speeds below 30 m.p.h, and some undesirable results at speeds beyond 50 m.p.h. These results point out the conflicting goals between operating the vehicle at speeds above the designed cruising speed during heavy traffic load, or at low speeds during adverse weather conditions, and ride comfort of the passengers.
R. ASHWORTH: A note on the selection o f gap acceptance cr#eria for traffic simulation studies. Transpn Res. 2, 171-175. A mathematical model has been constructed to demonstrate the bias which is introduced in the collection a n d presentation of gap acceptance data at a stop-sign controlled intersection. For the purpose of the model, it is assumed that traffic on the major road is randomly distributed and that driver gap acceptance characteristics follow a normal distribution curve with standard deviations. The model shows that the resulting gap acceptance curve is of the original form but displaced by an amount s~q, where q is the major road volume (veh/sec). This result has been confirmed by simulation studies carried out with traffic volumes ranging from 300 to 1500 veh/hr. It is considered that the existence of this bias necessitates care in the collection and combination of gap acceptance data at different levels of traffic volume and also requires a careful appraisal of the procedure used to simulate traffic movements at the intersection in order to ensure that the observed gap acceptance data are reproduced in the simulation model.
WILLIAM L. HOOPER: Transportation: burden or blessing to the urban environment? Transpn
Res. 2, 177-185. The relationship of u r b a n design to transportation planning is explored. Mobility is examined in terms of its contribution to environmental quality and a new measure of mobility is advanced to reflect the importance of access to work place, shopping place and other sites of functional activity. The role of the transport system expert as a member of an u r b a n environment design team is considered and conclusions are drawn relating to longterm transportation planning and experimentation.
NELSON M. ISADA: Effects o f speed and camber on the ride behavior o f a rapid transit vehicle traversing a dynamic roadway. Transpn Res. 2, 157-169. This paper deals with the analysis, based upon solutions obtained by computer, of the effects of vehicle speed and roadway beam camber on the vertical ride behavior of a rapid transit vehicle. The roadway is considered to be a simply supported beam in dynamic flexure which possesses inertia and equivalent viscous damping, whereas the vehicle is simulated as a four-degree-of-freedom system. F o r the vehicle-roadway system considered, it is found that camber is beneficial at cruising speeds (30-50 m.p.h.) but it produces larger r.m.s. (root mean square) and maximum (magnitude) pitch displacements at speeds below 30 m.p.h, and some undesirable results at speeds beyond 50 m.p.h. These results point out the conflicting goals between operating the vehicle at speeds above the designed cruising speed during heavy traffic load, or at low speeds during adverse weather conditions, and ride comfort of the passengers.
R. ASHWORTH: A note on the selection o f gap acceptance cr#eria for traffic simulation studies. Transpn Res. 2, 171-175. A mathematical model has been constructed to demonstrate the bias which is introduced in the collection a n d presentation of gap acceptance data at a stop-sign controlled intersection. For the purpose of the model, it is assumed that traffic on the major road is randomly distributed and that driver gap acceptance characteristics follow a normal distribution curve with standard deviations. The model shows that the resulting gap acceptance curve is of the original form but displaced by an amount s~q, where q is the major road volume (veh/sec). This result has been confirmed by simulation studies carried out with traffic volumes ranging from 300 to 1500 veh/hr. It is considered that the existence of this bias necessitates care in the collection and combination of gap acceptance data at different levels of traffic volume and also requires a careful appraisal of the procedure used to simulate traffic movements at the intersection in order to ensure that the observed gap acceptance data are reproduced in the simulation model.
WILLIAM L. HOOPER: Transportation: burden or blessing to the urban environment? Transpn
Res. 2, 177-185. The relationship of u r b a n design to transportation planning is explored. Mobility is examined in terms of its contribution to environmental quality and a new measure of mobility is advanced to reflect the importance of access to work place, shopping place and other sites of functional activity. The role of the transport system expert as a member of an u r b a n environment design team is considered and conclusions are drawn relating to longterm transportation planning and experimentation.