ITS Berkeley

Empirical Reassessment of Traffic Operations: Freeway Bottlenecks and the Case for HOV Lanes

Cassidy, Michael J.
Daganzo, Carlos F.
Jang, Kitae
Chung, Koohong
2006

An earlier empirical study of San Francisco Bay Area freeways concluded that HOV lanes unfavorably affect freeway traffic by creating congestion. That study attributed the observed congestion to HOV lanes and tentatively recommended their elimination over the full lengths of the freeways it examined; and even from all Bay Area freeways. It recognized, however, that its analysis is fragmentary and recommended further work to solidify its conclusions. This is logical since the study lacks a spatiotemporal analysis to pinpoint where and how congestion first forms (at bottlenecks).The present...

Macroscopic Modeling of Traffic in Cities

Geroliminis, Nikolas
Daganzo, Carlos F.
2007

Most of the existing models for large scale arterial networks are not realistic and appropriate to deal with crowded conditions. As an alternative, we propose observation-based models that circumvent the fragility problems of traditional models. Monitoring replaces prediction, and the system is repeatedly modified based on observations. To succeed this goal a city is modeled in an aggregated manner and relations between state variables are developed. Macroscopic control strategies are introduced which rely on real-time observation of relevant spatially aggregated measures of traffic...

Impacts of Lane Changes at Merge Bottlenecks: A Theory and Strategies to Maximize Capacity

Laval, Jorge
Cassidy, Michael
Daganzo, Carlos
Schadschneider, Andreas
Pöschel, Thorsten
2007

Recent empirical observations at freeway merge bottlenecks have revealed (i) a drop in the bottleneck discharge rate when queues form upstream, (ii) an increase in lane-changing maneuvers simultaneous with this “capacity drop”, and (iii) a reversal of the drop when the ramp is metered.

Counteracting the Bullwhip Effect with Decentralized Negotiations

Ouyang, Yanfeng
Daganzo, Carlos F.
2007

This paper shows how to reduce the bullwhip effect by introducing advance demand information (ADI) into the ordering schemes of supply chains. It quantifies the potential costs and benefits of ADI, and demonstrates that they are not evenly distributed across the chain. Therefore, market-based strategies to re-distribute wealth without penalizing any supplier are presented. The paper shows that if a centralized operation can eliminate the bullwhip effect and reduce total cost, then some of this reduction can also be achieved with decentralized negotiation schemes. Their performance is...

The Bullwhip Effect in Supply Chains with Stochastic Dynamics

Ouyang, Yanfeng
Daganzo, Carlos F.
2007

This paper analyzes the bullwhip effect in single-echelon supply chains operated nondeterministically. The supply chain is modeled as a Markovian jump linear system driven by arbitrary customer demands. The paper presents robust analytical conditions to diagnose the bullwhip effect, and bound its magnitude. The tests are independent of the customer demand. Examples are given. Policies that pass these tests, and thus avoid the bullwhip effect in random environments for arbitrary customer demands, are shown to exist. The paper also presents extended tests for multi-echelon chains.

Continuum Approximation Techniques for the Design of Integrated Package Distribution Systems

Smilowitz, Karen R.
Daganzo, Carlos F.
2007

Complex package distribution systems are designed using idealizations of network geometries, operating costs, demand and customer distributions, and routing patterns. The goal is to find simple, yet realistic, guidelines to design and operate a network integrated both by transportation mode and service level; i.e., overnight (express) and longer (deferred) deadlines. The decision variables and parameters that define the problem are presented along with the models to approximate total operating cost. The design problem is then reduced to a series of optimization subproblems that can be...

Urban Gridlock: Macroscopic Modeling and Mitigation Approaches

Daganzo, Carlos F.
2007

This paper describes an adaptive control approach to improve urban mobility and relieve congestion. The basic idea consists in monitoring and controlling aggregate vehicular accumulations at the neighborhood level. To do this, physical models of the gridlock phenomenon are presented both for single neighborhoods and for systems of inter-connected neighborhoods. The models are dynamic, aggregate and only require observable inputs. The latter can be obtained in real-time if the neighborhoods are properly instrumented. Therefore, the models can be used for adaptive control. Experiments should...

Deploying Lanes for High Occupancy Vehicles in Urban Areas

Cassidy, Michael J.
Daganzo, Carlos F.
2007

Simulations and field experiments in previous works suggest that a freeway’s general purpose lanes (those not dedicated to high occupancy vehicles) discharge vehicles from bottlenecks at an equal or higher average rate when one of the lanes is devoted to high occupancy vehicles than when it is not. This result was used in these previous works to develop formulae for the total discharge rate of bottlenecks, with and without dedicated lanes, as a function of the percentage of high occupancy vehicles in the traffic stream.This present paper extends these ideas by examining the effect of...

City-Scale Transport Modeling: An Approach for Nairobi, Kenya

Daganzo, C. F.
Li, Yuwei
Gonzales, Eric J.
Geroliminis, Nikolas
2007

Traffic congestion poses problems for cities around the world, especially in rapidly growing and motorizing cities like Nairobi, Kenya. We show here how we plan to use in the context of Nairobi a new theory that relates the mobility provided by a city’s street network to the number of vehicles on the network (including private cars and public transport) and to key aggregate descriptors of both the street infrastructure and the public transport services. Conventional micro-simulation models require vast quantities of data and produce unreliable detailed results. The new theory asserts that...

Spillovers, Merging Traffic and the Morning Commute

Lago, Alejandro
Daganzo, Carlos F.
2007

Theoretical studies of the morning commute for mono-centric cities have ignored that drivers choose their home departure times knowing that they must compete with other drivers for road space, which becomes scarcer with proximity to the center. This paper examines two important aspects of this competition: queue spillovers caused by insufficient road space, and merging interactions caused by the convergence of trips. For maximum transparency the paper focuses on an idealized two-origin, single-destination network with limited storage space because this system exhibits all the essential...