Traffic Theory

A Continuum Theory of Traffic Dynamics for Freeways with Special Lanes

Daganzo, Carlos F.
1997

This paper presents a generalized theory of kinematic waves for freeways with two vehicle types and a set of lanes reserved for one of the vehicle classes. The theory is not restricted to freeways on which the special lanes are clearly identified by signs and pavement markings; e.g. for high occupancy vehicles. It may also apply if the restrictions are self-imposed, such as would occur on a freeway segment upstream of a busy off-ramp where the existing traffic naturally avoids the ‘far-side’ lanes. Of particular interest are oversaturated time periods because the original theory of...

A Simple Physical Principle for the Simulation of Freeways with Special Lanes and Priority Vehicles

Daganzo, Carlos F.
Lin, Wei-Hua
Del Castillo, Jose M.
1997

This paper presents a simple physical principle that can be used to solve the kinematic wave problem for freeways with special lanes and priority vehicles. The principle is shown to yield the flows for all possible ‘Riemann problems’ arising in a homogeneous highway, so that its application in a simulation is equivalent to the Godunov ‘classic’ finite difference approximation method. The principle is appealing because its physical basis, unlike purely mathematical formulae, suggests a natural way in which boundary conditions for practical problems may be treated. Perhaps the IT principle...

The Netcell Simulation Package: Technical Description

Cayford, Randall
Lin, Wei-Hua
Daganzo, Carlos F.
1997

This report describes the NETCELL simulation package. NETCELL is a freeway network simulation program based on the cell transmission model which captures the dynamic evolution of multicommodity traffic over a freeway network with three-legged junctions in a way that is consistent with the hydrodynamic theory of highway traffic. NETVIEW is a graphical postprocessor for viewing NETCELL output files. This document discusses implementation of the programs in detail, including the cell representation for a freeway network with three-legged junctions, data and file structures, inputs and outputs...

An Enhanced Cell-Transmission Rule for Traffic Simulation

Daganzo, Carlos F.
1997

The Lagged Cell-Transmission Model

Daganzo, Carlos F.
1999

In cell-transmission models of highway traffic one partitions a highway into small sections (cells) and keeps track of the cell contents (number of vehicles) as time passes. The record is updated at closely spaced instants (clock ticks) by calculating the number of vehicles that cross the boundary separating each pair of adjoining cells during the corresponding clock interval. This paper shows that the accuracy of the cell-transmission approach is enhanced if the downstream density that is used to calculate the receiving flow(s) is read L clock intervals earlier than the current time...

A Behavioral Theory of Multi-Lane Traffic Flow Part I: Long Homogeneous Freeway Sections

Daganzo, Carlos F.
1999

This paper proposes a macroscopic behavioral theory of traffic dynamics for homogeneous, multi-lane freeways. The theory makes predictions for separate groups of lanes while recognizing that the traffic stream is usually composed of aggressive and timid drivers. Its principles are so simple that non-scientist drivers can understand them. The simplest version of the theory, which is described in its full complexity without calculus, is shown to be qualitatively consistent with experimental observations, including the most puzzling. Its predictions agree with the following phenomena: (i) the...

Access Control on Networks with Unique Origin–Destination Paths

Lovell, David J.
Daganzo, Carlos F.
2000

This paper presents improved time-dependent control strategies for small freeway networks with bottlenecks and unique origin–destination paths. It is assumed that there are no spill-overs from any of the freeway exits so that freeway queues and delays can be completely avoided by regulating access to the system so as to maintain bottleneck flows strictly below capacity. It is also assumed that the time-dependent origin–destination table and the time-dependent bottleneck capacities are known, although not always a priori. The proposed control strategies attempt to minimize the total delay (...

A Pareto Improving Strategy for the Time-Dependent Morning Commute Problem

Daganzo, Carlos F.
Garcia, Reinaldo C.
2000

This research shows that certain time-dependent congestion reduction schemes involving tolls have the potential for benefiting every driver even if the collected revenues are not returned to the payers. The paper considers a population of commuters who use a single bottleneck during the morning rush hour and try to arrive at work on time. It is assumed that the number of commuters is fixed (independent of the control strategy) and that each commuter wishes to pass through the bottleneck at a given time, which may differ across commuters. Commuters are otherwise identical. Each of them...

Moving Bottlenecks: A Theory Grounded on Experimental Observation

Munoz, Juan Carlos
Daganzo, Carlos F.
Taylor, Michael A. P.
2002

Reproducible Features of Congested Highway Traffic

Smilowitz, K. R.
Daganzo, Carlos F.
2002

Observation of a four-mile long, inhomogeneous, congested traffic stream revealed that vehicle accumulations between detectors vary with flow in a predictable way, and that a macroscopic kinematic wave with a reproducible speed exists in queues despite unusual traffic behavior. As a result, time-dependent vehicle trip times and accumulations inside long queues (and the queue length itself) can be predicted from readily available data without using any “degrees of freedom” to fit the parameters of a model. Experimental vehicle counts were within 20 vehicles of the predictions for over two...