Transportation Science

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Average Delay at an Unsignalized Intersection with Two Major Streams Each Having a Dichotomized Headway Distribution
Transportation Science - Tập 20 Số 4 - Trang 272-286 - 1986
R J Troutbeck
The average time a driver has to wait before he can cross two major streams has been a major performance indicator for unsignalized intersections. The equations presented in this paper give an estimate of this average delay as a function of the average delay to isolated minor stream vehicles (Adams' delay) and the degree of saturation of the minor stream (minor stream entry flow/maximum e...... hiện toàn bộ
Perceptual Thresholds in Car-Following—A Comparison of Recent Measurements with Earlier Results
Transportation Science - Tập 11 Số 1 - Trang 60-72 - 1977
Leonard Evans, Richard Rothery
The authors have previously conducted a field experiment to investigate the sensitivity of subjects to the sign of relative motion when following a vehicle. They interpreted their results in terms of responses to analytical functions of relative speed divided by spacing, or spacing change divided by spacing. In the present paper the remits of a number of other field, simulator, and labora...... hiện toàn bộ
Characterizing Traffic Conditions in Urban Areas
Transportation Science - Tập 18 Số 2 - Trang 101-140 - 1984
Robert K Herman, Siamak Ardekani
A series of vehicular traffic experiments conducted in Austin, Texas, shows the reasonableness of the two assumptions in the two-fluid (moving and stopped vehicles) model of town traffic. The observational data support the assumption that the average speed in an urban street network is proportional to the fraction of the vehicles moving raised to a power and is also in agreement with the ...... hiện toàn bộ
An Adaptive Dynamic Programming Algorithm for Dynamic Fleet Management, I: Single Period Travel Times
Transportation Science - Tập 36 Số 1 - Trang 21-39 - 2002
Gregory A. Godfrey, Warren B. Powell
We consider a stochastic version of a dynamic resource allocation problem. In this setting, reusable resources must be assigned to tasks that arise randomly over time. We solve the problem using an adaptive dynamic programming algorithm that uses nonlinear functional approximations that give the value of resources in the future. Our functional approximations are piecewise linear and natur...... hiện toàn bộ
Vehicle Routing with Stochastic Demands: Properties and Solution Frameworks
Transportation Science - Tập 23 Số 3 - Trang 166-176 - 1989
Moshe Dror, Gilbert Laporte, Pierre Trudeau
This paper considers the vehicle routing problem with stochastic demands. The objective is to provide an overview of this problem, and to examine a variety of solution methodologies. The concepts and the main issues are reviewed along with some properties of optimal solutions. The existing stochastic mathematical programming formulations are presented and compared and a new formulation is...... hiện toàn bộ
Computational Approaches to Stochastic Vehicle Routing Problems
Transportation Science - Tập 29 Số 4 - Trang 342-352 - 1995
Dimitris Bertsimas, Philippe Chervi, Michael D. Peterson
We report computational test results for several graph-based a priori heuristics for the Euclidean plane versions of two well-known stochastic optimization problems, the probabilistic traveling salesman problem (PTSP) and the probabilistic (or stochastic) vehicle routing problem (PVRP). These heuristics are termed a priori because they design vehicle routes prior to realization of demands...... hiện toàn bộ
Technical Note—Heuristics for Delivery Problems with Constant Error Guarantees
Transportation Science - Tập 24 Số 4 - Trang 294-297 - 1990
Kemal Altınkemer, Bezalel Gavish
In this paper Q Iterated Optimal Tour Partitioning, and Best Optimal Tour Partitioning algorithms are studied and analyzed for their worst case error. Both algorithms are based on partitioning an optimal traveling salesman tour in order to generate a feasible solution to the unit weight delivery problem. They have a worst case error bound of 2 − 1/Q where Q is the maximal number of custom...... hiện toàn bộ
An Adaptive Dynamic Programming Algorithm for the Heterogeneous Resource Allocation Problem
Transportation Science - Tập 36 Số 2 - Trang 231-249 - 2002
Warren B. Powell, Joel A. Shapiro, Hugo Simão
We consider an aggregated version of a large-scale driver scheduling problem, derived from an application in less-than-truckload trucking, as a dynamic resource allocation problem. Drivers are aggregated into groups characterized by an attribute vector which capture the important attributes required to incorporate the work rules. The problem is very large: over 5,000 drivers and 30,000 lo...... hiện toàn bộ
An Adaptive Dynamic Programming Algorithm for Dynamic Fleet Management, II: Multiperiod Travel Times
Transportation Science - Tập 36 Số 1 - Trang 40-54 - 2002
Gregory A. Godfrey, Warren B. Powell
In a companion paper (Godfrey and Powell 2002) we introduced an adaptive dynamic programming algorithm for stochastic dynamic resource allocation problems, which arise in the context of logistics and distribution, fleet management, and other allocation problems. The method depends on estimating separable nonlinear approximations of value functions, using a dynamic programming framework. T...... hiện toàn bộ
Discretization and Validation of the Continuum Approximation Scheme for Terminal System Design
Transportation Science - Tập 40 Số 1 - Trang 89-98 - 2006
Yanfeng Ouyang, Carlos F. Daganzo
This paper proposes an algorithm that automatically translates the “continuum approximation” (CA) recipes for location problems into discrete designs. It applies to terminal systems, but can also be used for other logistics problems. The study also systematically compares the logistics costs predicted by the CA approach with the actual costs for discrete designs obtained with the automate...... hiện toàn bộ
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