ITS Berkeley

Evaluation of Alternative AHS System Operating Concepts

Daganzo, Carlos F.
Cayford, Randall
Lin, Wei-Hua
1995

This paper focuses on technical and economic investigations of automated highway systems (AHS). It attempts to show that the actual viable implementation opportunities for AHS are scarce. The paper begins with an investigation that looks at realistic estimates of AHS capacity, interfacing with the local street system, and storage issues. The authors then identify criteria to help in determining which types of urban areas might be potential candidates for AHS technologies. Certain locations where AHS might be beneficial are identified, but doubt is raised regarding the extent of the...

A Pareto Optimum Congestion Reduction Scheme

Daganzo, Carlos F.
1995

This article shows that certain congestion reduction schemes have the potential for not penalizing anyone. The traditional social welfare approach is modified to address the distribution of gains and losses across the population. As a first step in this line of research, we consider a transportation system where congestion delay is simply given by a function of its user flow. We show that a particular pricing scheme with variable tolls, that can be viewed as hybrid between rationing and pricing, can benefit everyone (unlike pure pricing alone) even if the collected revenues are not...

Properties of Link Travel Time Functions Under Dynamic Loads

Daganzo, Carlos F.
1995

This article examines a general form of link travel time functions considered in the dynamic traffic assignment literature and shows that it only makes some physical sense in the special case where each function denotes either a link with no spatial dimension containing a point queue or a link with constant travel time and no queueing. Roadway segments exhibiting both phenomena must be represented by two links in series.

The Cell Transmission Model, Part II: Network Traffic

Daganzo, Carlos F.
1995

This article shows how the evolution of multi-commodity traffic flows over complex networks can be predicted over time, based on a simple macroscopic computer representation of traffic flow that is consistent with the kinematic wave theory under all traffic conditions. The method does not use ad hoc procedures to treat special situations. After a brief review of the basic model for one link, the article describes how three-legged junctions can be modeled. It then introduces a numerical procedure for networks, assuming that a time-varying origin-destination (O-D) table is given and that the...

A Finite Difference Approximation of the Kinematic Wave Model of Traffic Flow

Daganzo, Carlos F.
1995

This article shows that if the kinematic wave model of freeway traffic flow in its general form is approximated by a particular type of finite difference equation, the finite difference results converge to the kinematic wave solution despite the existence of shocks in the latter. This result, which applies to initial and boundary condition problems with and without discontinuous data, is shown not to hold for other commonly used finite difference schemes. In the proposed approximation, the flow between two neighboring lattice points is the minimum of the two values returned by: 1.(a) a “...

Requiem for Second-Order Fluid Approximations of Traffic Flow

Daganzo, Carlos F.
1995

Although the “first order” continuum theory of highway traffic proposed by Lighthill and Whitham (1955) and Richards (1956)—the LWR model—can predict some things rather well, it is also known to have some deficiencies. In an attempt to correct some of these, “higher order” theories have been proposed starting in the early 70s. Unfortunately, the usefulness of these improvements can be questioned. This note describes the logical flaws in the arguments that have been advanced to derive higher order continuum models, and shows that the proposed high order modifications lead to a fundamentally...

The Variance of the Number of Customers in an Infinite-Server Queueing System with an Arbitrarily Correlated Arrival Process

Daganzo, Carlos F.
Diez-Roux, Esteban
1995

Motivated by a container storage problem at seaports, this paper examines the infinite-server queueing model with a (second order) stationary but arbitrarily correlated arrival process. It starts with a description of the application context, including an explanation of why non-standard inputs and service times arise in certain container storage problems. As further illustration, formulas characterizing the input and service processes for a particular situation are then presented and justified, together with the simple container accumulation variance formula that follows from the general...

Steady State Conditions on Automated Highways

del Castillo, Jose M.
Lovell, David J.
Daganzo, Carlos F.
1995

This paper is concerned with technical investigations of traffic operations on automated highways. Estimates are made of the steady-state capacity of such freeways, paying particular attention to the effect of entry and exit maneuvers. The possibility of scheduling departing vehicles appropriately into platoons to minimize extraneous maneuvers is investigated. Characteristics of urban areas likely to be candidates for automated freeways are discussed, and some shortcomings of automated freeways, vis-à-vis conventional freeways, are pointed out. Finally, some areas of future research needs...

Dymanic Traffic Assignment With Queues For ATIS : Final Report For Project MOU 90

Daganzo, Carlos F.
1996

This document reports on a project whose overall objective was to develop a traffic flow model capable of predicting the evolution of multicommodity (multiple destination) network traffic flows consistent with the hydrodynamic theory of traffic flow. The output of this research should enhance the realism of modeling capabilities in representing traffic flows and especially physical queues. This should provide a solid platform for the evaluation of Intelligent Transportation Systems (ITS) improvements, environmental impacts, and dynamic control strategies. In particular, it holds...