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Open Access Publications from the University of California

Recent Work

The UC Berkeley Center for Future Urban Transport was established in 2004 after the Volvo Research and Educational Foundations designated it as a Volvo Center of Excellence in a competition involving a large field of international candidates. It is housed at the Institute of Transportation Studies at the University of California, Berkeley, and its director is Carlos Daganzo, Professor of Civil and Environmental Engineering.

The Center's mission is to study the mutual interdependence of urban transportation policy and technology and use the understanding of that concept to devise sustainable transportation strategies for the world's cities.

It addresses this undertaking on three levels:

  • strategic, so that the research is guided by a city's vision of its own future;
  • tactical, where policies are tailored for specific environments; and
  • operational, where technologies are developed and the results fed back into tactical-level decisions.

The Center's research is divided into five research areas:

  • Mobility & Accessibility
  • Adapting to Urban Form
  • Telework Solutions
  • Congestion Mitigation
  • Wireless Infrastructure

Cover page of Strategies for Mitigating Impacts of Near-Side Bus Stops on Cars

Strategies for Mitigating Impacts of Near-Side Bus Stops on Cars

(2012)

"Near-side stops" are bus stops located a short distance upstream of a signalized intersection. A bus dwelling at a near-side stop can impede queued cars upstream as they discharge during their green time at the intersection. Added car delays and residual queues can result. All else equal, the closer the stop’s location to the intersection, the greater the potential damage to car traffic. Models for locating these near-side stops to achieve target levels of residual queueing among cars are formulated using kinematic wave theory. This same approach was also used to develop a strategy for further mitigating residual car queues by temporarily detaining some buses from reaching the stop. This bus-holding strategy can be applied selectively, so that the times that held buses depart from the stop are not affected. The strategy therefore will not delay buses over the longer run. Assessments indicate that this holding strategy can significantly reduce instances of car delays and residual queueing, especially for stops that are located very close to their intersections.

Cover page of Dual Influences on Vehicle Speeds in Special-Use Lanes and Policy Implications

Dual Influences on Vehicle Speeds in Special-Use Lanes and Policy Implications

(2011)

Slow speeds in a special-use lane, such as a carpool (HOV) or bus lane, can be due to both high demand for that lane and slow speeds in the adjacent regular-use lane. These dual influences are confirmed from months of data collected from all freeway carpool facilities in the San Francisco Bay Area. Both influences hold for other types of special-use lanes, including bus lanes. New US regulation stipulating that most classes of low-emitting vehicles, or LEVs, be banned from slow-moving carpool lanes. While LEVs invariably constitute only about 1 percent of the freeway traffic demand in the San Francisco Bay Area, forcing some or all of these vehicles to regular-use lanes can significantly add to regular-lane congestion, and that this, in turn, can also be damaging to vehicles that continue to use the carpool lanes. Counterproductive outcomes of this kind are predicted first by applying kinematic wave analysis to a real Bay Area freeway. The site stands to suffer less from the regulation than will others in the region but the site’s people-hours and vehicle-hours traveled during the rush are predicted to each increase by more than 10 percent and that carpool-lane traffic will share in the damages. Real data from the site support these predictions. Further parametric analysis of a hypothetical, but more generic freeway system indicates that these kinds of negative outcomes will be widespread. Constructive ways to amend the new regulation are discussed, as are promising strategies to increase the vehicle speeds in carpool lanes by improving the travel conditions in regular lanes.

Cover page of Urban Densities and Transit: A Multi-dimensional Perspective

Urban Densities and Transit: A Multi-dimensional Perspective

(2011)

This paper investigates the relationship between transit and urban densities in the United States. An analysis of light rail systems finds that a residential density of about 30 people per gross acre near stations is needed to in order to make them among the top 25 percent of rail transit investments in terms of cost effectiveness; for heavy rail systems, the density is 45 people per gross acre. Increasing density around stations would greatly increase ridership, particularly when jobs are located within one-quarter mile of the stations and housing is located within one-half mile. Stakeholders in the small city of Stockton found high levels of density unacceptable, and supported transit improvements, such as bus rapid transit, only when there would be no impact on private vehicle traffic.

Cover page of Morning Commute with Competing Modes and DistributedDemand: User Equilibrium, System Optimum, and Pricing

Morning Commute with Competing Modes and DistributedDemand: User Equilibrium, System Optimum, and Pricing

(2011)

The morning commute problem for a single bottleneck is extended to model mode choice in an urban area with time-dependent demand. This extension recognizes that street space is shared by cars and public transit. It is assumed that transit is operated independently of traffic conditions, and that when it is operated it consumes a fixed amount of space. As a first step, a single fixed-capacity bottleneck that can serve both cars and transit is studied. Commuters choose which mode to use and when to travel in order to minimize the generalized cost of their own trip. The transit agency chooses the headway and when to operate. Transit operations reduce the bottleneck’s capacity for cars by a fixed amount. The following results are shown for this type of bottleneck: 1. If the transit agency charges a fixed fare and operates at a given headway, and only when there is demand, then there is a unique user equilibrium. 2. If the transit agency chooses its headway and time of operation for the common good, then there is a unique system optimum. 3. Time-dependent prices exist to achieve system optimum. Finally, it is also shown that results 2 and 3 apply to urban networks.

Cover page of A Dynamic Holding Strategy to Improve Bus ScheduleReliability and Commercial Speed

A Dynamic Holding Strategy to Improve Bus ScheduleReliability and Commercial Speed

(2011)

Bus systems are naturally unstable. Without control, the slightest disturbance to bus motion can cause buses to bunch, reducing schedule reliability. Holding strategies can eliminate this instability. However, the conventional schedule-based holding method requires too much slack time, which slows buses. This delays on-board passengers and increases operating costs. This paper studies a family of dynamic holding strategies that use the current state of all buses, as well as a virtual schedule. The virtual schedule is introduced whether the system is run with a published schedule or not. We found that with this control method, which we term general control method, buses can both closely adhere to schedule and maintain regular headways without too much slack. Thus the general control idea is applicable to bus lines with both long and short headways. Although the optimal set of control parameters can be found numerically, a one-parameter version of the control method can be optimized in closed form. This simple method was shown to be near-optimal. To put it in practice, one only needs the arrival times of the current bus and the preceding bus relative to the virtual schedule. This simple method was found to outperform alternative control methods (i.e., require less slack for the same headway variance). While the paper mostly focuses on recurrent small disturbances under quasi-deterministic demand, it also shows that the proposed control method can deal with large disturbances.

Cover page of Innovative Bus-Lane Deployments in Amman: Proposed Field Experiments

Innovative Bus-Lane Deployments in Amman: Proposed Field Experiments

(2010)

Innovative strategies for deploying bus lanes are proposed for field tests in Amman, Jordan. The objective is to reduce delays to buses in the network while minimizing delays to other vehicular traffic. The proposed strategies may be far better options than conventional, static bus lanes, given the test site’s large car demand and low bus frequency. The experiment is designed to be conducted in simple, safe ways, without the need for investment in permanent infrastructure.

Cover page of Clockwise Hysteresis Loops in the MacroscopicFundamental Diagram

Clockwise Hysteresis Loops in the MacroscopicFundamental Diagram

(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 tends more strongly toward unevenness because very congested areas clear more slowly than less congested areas. Since it is known that uneven congestion distributions reduce network flows, it follows that lower network flows should arise during recovery, resulting in clockwise loops. Fortunately, in sufficient numbers, drivers that choose routes adaptively to avoid congested areas help to even out congestion during recovery, increasing flow. Thus, clockwise loops are less likely to occur when driver adaptivity is high.

Cover page of Toward Green TODs

Toward Green TODs

(2010)

Green Transit Oriented Developments (TODs) shrink environmental footprints by reducing Vehicle Kilometers Traveled (VKT)/ Vehicle Miles Travled (VMT) and incorporating green urbanism and architecture in community designs. Synergies from combining TOD and green urbanism derive from increased densities, which promote transit usage and conserve heating/cooling expenses; mixed land uses which promote non-motorized transportation and limited-range electric vehicles; reduced impervious parking services matched by increased open space and community gardens; and, opportunities for generating solar power from photovoltaics atop rail-stop canopies. The carbon footprints of Green TODs can be 35% less than those of conventional developments. Experiences with Green TODs are reviewed for urban regeneration projects in Sweden, Germany, and Australia. The paper concludes with ideas on moving Green TODs from theory to practice.

Cover page of Deploying Underutilized Bus Lanes at Key Nodes in a Road Network

Deploying Underutilized Bus Lanes at Key Nodes in a Road Network

(2010)

The authors of this working paper explain that the operation of buses in mixed traffic flow can be impeded by congestion, leading to unreliable and slow service. Similarly, buses that stop frequently for passengers interfere with the flow of general traffic. Dedicated lanes provide a means for buses to bypass car queues, but in cases where bus flow is low, converting a general purpose lane to a bus-only lane will delay car traffic. The authors describe innovative schemes for deploying bus lanes to serve low bus demand intermittently. Strategies to deploy underutilized bus lanes will be systematically examined and field-tested in Amman, Jordan. A final report will include guidelines for deploying underutilized bus lanes that reduce or eliminate bus delays while minimizing the additional delay imparted to cars.

Cover page of A congestion mechanism for uphill expressways, Part I: the shoulder lane "release valve"

A congestion mechanism for uphill expressways, Part I: the shoulder lane "release valve"

(2010)

A mechanism is unveiled by which congestion forms and persists near the base of an uphill expressway segment, causing significant reductions in output flow. The traffic condition in the expressway's shoulder lane is key to the mechanism. When shoulder-lane flow was low, drivers maneuvered around speed disturbances that periodically arose in the median lane. The shoulder lane accommodated high rates of vehicle migrations, thus acting as a "release valve" for the excess accumulation created by the speed disturbances. The release valve failed only when demand increased later in the rush. The resulting higher flows in the shoulder lane impeded drivers' attempts to maneuver around the median-lane speed disturbances that occurred thereafter. These attempts disrupted traffic and spread the excess accumulation laterally across all lanes. When this queue filled the approach to the hill, vehicles arrived to its base at low speeds. This impeded vehicle ascent; output flow dropped by about 10%; and this state of affairs persisted for the remainder of the rush.

The more conspicuous details of this mechanism were observed in loop detector data measured over many days at the site, and are consistent with observations previously made at other sites. The more subtle details became visible by examining thousands of vehicle trajectories extracted from a series of eleven roadside video cameras. Many of the subtleties are compatible with an existing theory of multi-lane traffic. All of this suggests that the present findings can be generalized to other uphill expressway segments. Practical implications are discussed.