ITS Berkeley

Exploring the Effect of Turning Maneuvers and Route Choice ona Simple Network

Gayah, Vikash V.
Daganzo, Carlos F.
2010

A simple symmetric network consisting of two tangent rings on which vehicles obey the Kinematic Wave Theory of traffic flow and can switch rings at the point of tangency is studied. An online adaptive simulation reveals that if there is any turning whatsoever the two-ring system becomes unevenly loaded for densities greater than the optimal density. This reduces flow. Furthermore, the two-ring system jams at significantly lower densities than the maximum density possible.

Clockwise Hysteresis Loops in the MacroscopicFundamental Diagram

Gayah, Vikash V.
Daganzo, Carlos F.
2010

A recent study reported that the Macroscopic Fundamental Diagram of a medium size city exhibited a clockwise hysteresis loop on a day in which a major disturbance caused many drivers to switch to unfamiliar routes. This paper shows that clockwise loops are to be expected when there are disturbances, especially if the disturbances cause a significant fraction of the drivers to not change routes adaptively. It is shown that when drivers are not adaptive networks are inherently more unstable as they recover from congestion than as they are loaded. In other words, during recovery congestion...

On the Stability of Freeway Traffic

Daganzo, Carlos F.
2010

Traffic flow theory is used to analyze the spatio-temporal distribution of flow and density on closed loop homogeneous freeways with many ramps, which produce inflows and allow outflows. It is shown that if the on-ramp demand is space-independent then this distribution tends toward uniformity in space if the freeway is either: (i) uncongested; or (ii) congested with queues on its on-ramps and enough inflow to cause the average freeway density to increase with time. In all other cases, including any recovery phase of a rush hour where the freeway's average density declines, the distribution...

Public Transportation Systems: Basic Principles of System Design, Operations Planning and Real-Time Control

Daganzo, Carlos F.
2010

This document is based on a set of lecture notes prepared in 2007-2010 for a University of California, Berkeley graduate course, Public Transportation Systems, a course targeted to first year graduate students with diverse academic backgrounds. Systems are examined in order of increased complexity so that generic insights evident in simple systems can be put to use as knowledge building blocks for the study of more complex systems. The document is organized in eight modules: five on planning (general, shuttle systems, corridors, two dimensional systems, and unconventional transit); two on...

Public Transportation Systems: Mini-Projects and Homework Exercises

Gonzales, Eric J.
Pilachowski, Josh
Gayah, Vikash V.
Cassidy, Michael
Daganzo, Carlos F.
2010

The Course Notes for a graduate-level course in Public Transportation include seven homework exercises and three mini-projects. Homework topics include optimization, point-to-point travel, congestion relief, designing a feeder bus system, demand-responsive transit, and bus pairings. The mini-projects involve bus rapid transit, designing a transit network, and bus and driver assignment.

On the Allocation of City Space to Multiple Transport Modes

Gonzales, Eric J.
Geroliminis, Nikolas
Cassidy, Michael J.
Daganzo, Carlos F.
2010

This paper analyzes urban multimodal transportation systems in an aggregated way. To describe the aggregate behavior of traffic in cities, use is made of an idea that is now receiving some attention: the macroscopic fundamental diagram (MFD). We demonstrate through simulation how the MFD can be used to monitor and control a real network, in this case a portion of San Francisco, using readily available input data. We then show how different modes interact on the same network and discuss how these interactions might be incorporated into an MFD for multimodal networks. The work unveils two...

Multimodal Transport in Nairobi, Kenya: Insights and Recommendations with a Macroscopic Evidence-Based Model

Gonzales, Eric J.
Chavis, Celeste
Li, Yuwei
Daganzo, Carlos F.
2011

The limited street network in Nairobi, Kenya, is crowded with cars and matatus (informal transit). This paper studies the existing traffic performance using traffic simulation. Despite the poorly connected, asymmetric street network, there is a consistent relationship between aggregated traffic variables for the city center, namely the number of vehicles circulating in the network and the rate at which trips reach their destinations. This relation is called a macroscopic fundamental diagram (MFD), and shows how the capacity of Nairobi's streets compares to the capacity of streets in...

Robust Stability Analysis of Decentralized Supply Chains

Ouyang, Yanfeng
Daganzo, Carlos F.
Kempf, Karl G.
Keskinocak, Pinar
Uzsoy, Reha
2011

This chapter summarizes recent findings on the bullwhip effect in decentralized multi-echelon supply chains based on a system-control approach. The influence of the supply chain operation (e.g., ordering policy and lead time) is separated from that of the customer demand. Robust results that hold for any customer demand are derived for both deterministically and stochastically operated chains. We demonstrate the importance of robust analysis. It is shown that instability is an inherent property of the system, e.g., of the ordering policies used by the suppliers, but it is independent of...

Macroscopic Fundamental Diagrams for Freeway Networks: Theory and Observation

Cassidy, Michael J.
Jang, Kitae
Daganzo, Carlos F.
2011

Macroscopic fundamental diagrams (MFDs), which relate the total time spent to the total distance traveled, are explored for freeway networks. It is proposed that these macrolevel relations should be observed if the data come from periods when all lanes on all links throughout the network are in either the congested or the uncongested regime. The theory pertains to freeway networks of any size, even when they are inhomogeneously congested and the data are variable in time. Analysis of vehicle trajectories from two freeway stretches of modest physical length supports this theory. Study...

Macroscopic Relations of Urban Traffic Variables: Bifurcations, Multivaluedness and Instability

Daganzo, Carlos F.
Gayah, Vikash V.
Gonzales, Eric J.
2011

Recent experimental work has shown that the average flow and average density within certain urban networks are related by a unique, reproducible curve known as the Macroscopic Fundamental Diagram (MFD). For networks consisting of a single route this MFD can be predicted analytically; but when the networks consist of multiple overlapping routes experience shows that the flows observed in congestion for a given density are less than those one would predict if the routes were homogeneously congested and did not overlap. These types of networks also tend to jam at densities that are only a...