Traffic Operations and Management

Traffic Delay at Unsignalized Intersections: Clarification of Some Issues

Carlos Daganzo
1977

Investigations in this area have been directed at finding the delay to a motorist who arrives at an intersection and wishes to cross a high-priority traffic stream. In this paper two conceptual errors that have appeared in some past publications are identified and corrected.

The Uniqueness of a Time-Dependent Equilibrium Distribution of Arrivals at a Single Bottleneck

Carlos Daganzo
1985

Motorists going through a bottleneck during the morning rush hour have to time their departure times to ensure they arrive to work at a reasonable time. Traffic and congestion levels at the bottleneck depend on the motorists' work schedule and the disutility of unpunctuality. This paper shows that, under certain conditions, there is only one equilibrium order of arrivals; an order under which motorists do not have an incentive to jockey for position in the queue.

Modeling Distribution Problems with Time Windows: Part I

Carlos Daganzo
1987

This paper shows how distribution problems with delivery time constraints can be modeled approximately with just a few variables. Its objective is neither to develop a scheduling algorithm nor an exact predictive method; rather, it is to illustrate some trade-offs and principles that can be used for planning and algorithm development. A workday is divided into time periods. Time windows are modeled by specifying the period in which a vehicle should visit each customer. (The companion paper explores scenarios where many customers do not specify a time window, and thus, it is advantageous...

The Break-Bulk Role of Terminals in Many-to-Many Logistic Networks

Carlos Daganzo
1987

This paper examines the structure of many-to-many logistics networks. Using as little data as possible, it attempts to answer macroscopic questions such as: How many terminals should be used? Should they be used at all? What should be the frequency of service? Although such a problem could be formulated with a large number of parameters and data, we show that near-optimal network structures can be characterized by two dimensionless constants which can be determined from the data (e.g., from the value of the items carried, the number of origins, the size of the service region, etc …). The...

Modeling Distribution Problems with Time Windows. Part II: Two Customer Types

Carlos Daganzo
1987

This paper extends the results of a previous study concerning distribution with time windows. It is recognized that customers who do not need to be allocated to a time window should receive different service than the rest. Three strategies were studied to accomplish that: stratified service, discriminating service, and staggered and discriminating service. Of these, the last strategy yields the lowest local distribution distance per customer, a distance which can be less than half that for the strategy explained in the previous paper (joint service). Stratified service, however, can yield...

Restricting Road Use Can Benefit Everyone

Carlos Daganzo
1992

This paper seeks congestion reduction schemes that do not penalize anyone. It shows that a combination of rationing and pricing (unlike congestion pricing alone) can benefit everyone even if the collected revenues are not returned to the population. The simple conditions under which this is possible are identified. Little data are needed to choose a proper policy. Examples are given.

Restricting Road Use Can Benefit Everyone, Part II: Time-of-Day Restrictions that Encourage Earlier Arrivals

Carlos Daganzo
1992

This research considers a less restricting rationing scheme where a restriction would mean that passage through the bottleneck is banned after a certain time of the day (e.g. the start of the rush hour) but not before that time. Conservatively, we assume that the ban remains in force even after the conclusion of the rush, although in practice one would like to terminate it earlier. (This assumption limits the benefits that can be gained from control as it discourages people from delaying their arrival in order to avoid the queue.) Despite this inefficiency, the scheme is shown to...

The Cell Transmission Model. Part I: A Simple Dynamic Representation of Highway Traffic

Carlos Daganzo
1993

This paper presents a simple representation of traffic on a highway with a single entrance and exit. The representation can be used to predict traffic's evolution over time and space, including transient phenomena such as the building, propagation and dissipation of queues. The easy-to-solve difference equations used to predict traffic's evolution are shown to be the discrete analog of the differential equations arising from a special case of the hydrodynamic model of traffic flow. The proposed method automatically generates appropriate changes in density at locations where the...

Effect of Modeling Assumptions on Evolution of Queues in a Single Corridor

Carlos Daganzo
Lin, Wei-Hua
1994

A qualitative description is presented of queuing patterns under an idealized scenario analogous to the evolution of traffic congestion during the morning peak hour in a long corridor leading to a single destination. The simplicity of the scenario allows the results to be verified independently by hand. Initially the corridor is assumed to consist of a single freeway. Traffic is generated at the freeway's many on-ramps during a short period and then is assumed to subside. Capacity limitations create queues on the ramps and the freeway, whose evolution is then described. A special...

The Cell Transmission Model: Network Traffic

Carlos Daganzo
1994

This paper shows how the evolution of multicommodity 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. After a brief review of the basic model for one link, the paper describes how three-legged junctions can be modeled. It then introduces a numerical procedure for networks, assuming that a time-varying origin-destination table is given and that the proportion of turns at every junction is known. These assumptions are reasonable...