ITS Berkeley

Models of Bus Queueing at Curbside Stops

Gu, Weihua
Cassidy, Michael J.
Li, Yuwei
2015

We consider curbside bus stops of the kind that serve multiple bus routes and that are isolated from the effects of traffic signals and other stops. A Markov chain embedded in the bus queueing process is used to develop steady-state queueing models of this stop type, as illustrated by two special cases. The models estimate the maximum number of buses that can arrive at and serve a stop and still satisfy a specified target of average bus delay. These models can be used to determine, for example, a stop’s suitable number of bus berths, given the bus demand and the specified delay target. The...

Effects of Segregating Buses and Cars in a Congested, Non–Steady-State Street Network

Saade, Nathalie
Cassidy, Michael J.
Gu, Weihua
2015

Much of the literature on exclusive bus lanes pertains to how these lanes might induce shifts in mode choice by prioritizing bus travel, sometimes at the expense of degrading travel by car; for example, see Basso et al. (1). A separate line of research theorized that the conversion of regular-use lanes to bus-only lanes can, in certain circumstances, improve travel for cars as well as buses, even in the absence of modal shifts (2). By removing buses from queues and putting them in their own, faster-moving lanes, target service frequencies can be maintained with fewer buses; thus, fewer bus...

A Problem of Limited-Access Special Lanes. Part I: Spatiotemporal Studies of Real Freeway Traffic

Cassidy, Michael J.
Kim, Kwangho
Ni, Wei
Gu, Weihua
2015

Most special-use freeway lanes in the US, whether reserved for carpools, toll-paying commuters or both, are physically separated from the adjacent regular-use lanes by some form of barrier. Vehicle movements in and out of a special lane of this type are permitted only at select access points along the route. The barrier at each select point might open for a distance of 400m or so. Limiting access in this way is said to reduce the “turbulence” that might otherwise occur were the special lane not to have a barrier, such that vehicles could instead enter or exit that lane anywhere along its...

A Problem of Limited-Access Special Lanes. Part II: Exploring Remedies via Simulation

Ni, Wei
Cassidy, Michael J.
Kim, Kwangho
Gu, Weihua
2015

Spatiotemporal analyses of freeway sites in Part I have shown that special-lane access points are prone to become bottlenecks. These can degrade traffic flows, sometimes in all lanes. Part II explores select impacts of re-designing the means of entering and exiting a special lane, and of altering the policy governing its use. Parametric tests were conducted using a computer simulation model that was calibrated to one of the sites studied in Part I; one with a buffer-separated carpool lane. Though less reliable than what might have been observed via experiments in real settings, the...

Exploring Alternative Service Schemes for Busy Transit Corridors

Gu, Weihua
Amini, Zahra
Cassidy, Michael J.
2016

Transit systems in which buses or trains always visit each and every stop along corridors are compared against those that feature two alternative vehicle-dispatching schemes. The alternatives entail so-called skip-stop and express/local services. Continuous models found in the literature are expanded so that the alternatives could be compared under a wider array of options. Comparisons are separately drawn for systems that feature buses, BRT and metro-rail trains, both for cities that are wealthy and for those that are not. Idealizations in regard to travel demand and route symmetry are...

A Low-Cost Alternative for Higher Capacities at Four-way Signalized Intersections

Kozey, Peter
Xuan, Yiguang
Cassidy, Michael J.
2016

Protecting left-turn movements on all four approaches to a signalized intersection conventionally requires a minimum of two extra phases per cycle. Losses in capacity often result. Various intersection designs have been proposed to combat those losses. Perhaps the best known of these designs is the continuous flow intersection. It features specially-configured approach lanes and mid-block pre-signals. These enable opposing left-turn and through-moving vehicles to proceed through the intersection free of conflicts, and without need for additional protected-turn phases. The present paper...

Cordon Control with Spatially-Varying Metering Rates: A Reinforcement Learning Approach

Ni, Wei
Cassidy, Michael J.
2019

The work explores how Reinforcement Learning can be used to re-time traffic signals around cordoned neighborhoods. An RL-based controller is developed by representing traffic states as graph-structured data and customizing corresponding neural network architectures to handle those data. The customizations enable the controller to: (i) model neighborhood-wide traffic based on directed-graph representations; (ii) use the representations to identify patterns in real-time traffic measurements; and (iii) capture those patterns to a spatial representation needed for selecting optimal cordon-...

City-Wide Traffic Control: Modeling Impacts of Cordon Queues

Ni, Wei
Cassidy, Michael
2019

Optimal cordon-metering rates are obtained using Macroscopic Fundamental Diagrams in combination with flow conservation laws. A model-predictive control algorithm is also used so that time-varying metering rates are generated based on their forecasted impacts. Our scalable algorithm can do this for an arbitrary number of cordoned neighborhoods within a city. Unlike its predecessors, the proposed model accounts for the time-varying constraining effects that cordon queues impose on a neighborhood’s circulating traffic, as those queues expand and recede over time. The model does so at every...

Achieving Higher Taxi Outflows from a Congested Drop-off Lane: A Simulation-Based Policy Study

Yang, Fangyi
Gu, Weihua
Cassidy, Michael
Li, Xin
Li, Tiezhu
2019

We examine special lanes used by taxis and other shared-ride services to drop-off patrons at airport and rail terminals. Vehicles are prohibited from overtaking each other within the lane. They must therefore wait in a first-in-first-out queue during busy periods. Patrons are often discharged from vehicles only upon reaching a desired drop-off area near the terminal entrance. When wait times grow long, however, some vehicles discharge their patrons in advance of that desired area. A train station in Eastern China is selected as a case study. Its FIFO drop-off lane is presently managed by...

Optimal Design of Transit Networks Fed by Shared Bikes

Wu, Liyu
Gu, Weihua
Fan, Wenbo
Cassidy, Michael J.
2020

Transit systems are designed in which access and egress can occur via a shared-bike service. Patrons may walk to shared-bike docking stations nearest their origins, and then cycle to their nearest transit stations where they deposit the bikes. The travel pattern is reversed when patrons cycle from their final transit stations on to their destinations. Patrons choose between this option and that of solely walking to or from transit stations. Shared bikes are priced to achieve the system-optimal assignment of the two feeder options. Transit trunk-line networks are laid-out in hybrid fashion...