Traffic Engineering

I-580 Variable Toll Lanes One Year On

I580 Monday night lights flickr photo by Images by John 'K' shared under a Creative Commons (BY-NC-ND) license

It's been a year since the variable toll express lanes on I-580 through the Tri-Valley region were rolled out, and initial results are in. As reported in the San Francisco Chronicle

Since the combination express and carpool lanes opened in February 2016 on I-580, along the main route between the Bay Area and the Central Valley, more than 7.6 million drivers have taken advantage of them, according to a report released Thursday by the Alameda County Transportation Commission, which operates the lanes.

You can read the report here

As toll roads are used more often as a tool in transportation demand management, there is more data available for comprehensive evaluations of road pricing systems. As transportation funding evolves with a greater reliance on public-private partnerships that will often rely on tolls for cost recovery, it is important to understand how they will affect travel demand.  In the case of 580, they look to be a hit.

Closed July 1-July 4

flickr photo shared by m01229 under a Creative Commons ( BY ) license

The ITS Library will be closed Friday July 1 for maintenance and Monday July 4 for the holiday. We will resume regular hours on Tuesday, July 5. 

This weekend, if you are going to a fireworks display, stay safe and sane while you sit in traffic leaving the event. There has been some research in how smart parking can help these kinds of events and how mobile networks can be leveraged to detect congestion more accurately. Crowd-sourced probe data can also be used to monitor the situation. And in areas where it's available bike share data can sense the pulse of activity, like Washington D.C. and the fireworks display at the Capitol Mall. 

Bus Bunching Explained Visually


Any bus rider knows what a problem bus bunching can be. (Anybody riding AC Transit's 51B to campus lives with this daily.) It's a popular research topic, with many articles and reports exploring the causes and solutions to prevent bunching.

ITS PhD student Lewis Lehe and designer Dennys Hess have developed visualization to explain why bus bunching happens. (You need to use Chrome.) Go try it out. CityLab and Metafilter are talking about it.  

Lehe has made many other visualizations explaining transportation phenomena like gridlock vs. bottlenecks and traffic waves. You can see more of his work on

Everybody loves bus bunching.

Corporation Atlanteans at Moreton Shore

Or more realistically, everybody loves to complain about bus bunching - when two or more buses (usually on the same line) should be evenly spaced out, but are right behind one another. Here around UC Berkeley AC Transit's 51b in the line most people complain about bunching (they're working on it!), but every transit systems has its own problem line(s). 

Earlier this week WBEZ's Curious City examines bus bunching in Chicago. They provide an easy to understand animation that demonstrates how minor service delays cascade to bus bunching. Bookmark it to share with your friends next time they lament about the topic. 

The topic is also beloved by transit researchers, particularly at ITS Berkeley. From systematic analysis of why bunching occurs to ways to solve the problem. And as always, you can find more research on bus bunching at TRID

Institute of Transportation Studies Friday Seminar: Lane Changing - Mysteries on Behavior and Modelling

Changing lanes

This week's Friday Transportation Seminar is about ellusive lane changing behaviors. Victor Knoop, Assistant Professoor of Transport & Planning at TU Delft will present, "Lane Changing - Mysteries on Behavior and Modelling."

Traffic congestion often is related to lane changes - at a lane drop bottleneck, on ramp, or weaving section. It is therefore essential to have a good description of the lane change maneuvers performed by drivers. Whereas much attention has been given to car-following behavior (how much distance do people keep), lane changing did not get the same amount of attention. This seminar will touch upon three aspects related to lane changing. Firstly, a large-scale data analysis shows that simple concepts of trying to go to a faster lane combined with gap accepting does not provide a satisfactory model. In the seminar outcomes of the data analysis are shown at it is discussed what can be learned from it. Secondly, calibration and validation are required for any model, but there is no standardized method for calibrating lane-change models. It will be shown that the methods have been chosen carefully. Thirdly, the differences in driving strategy between drivers with regard to lane changing are discussed.

The Friday Transportation Seminar takes place on September 19, 2014 from 4:00-5:00 PM in 290 Hearst Memorial Mining Building. Cookie Hour immediately precedes it at 3:30 PM in the same location. (Note: Cookie Hour is not in the library!) There will also be a no-host Happy Hour at LaVal's at 5:00 PM.

Institute of Transportation Studies Friday Seminar: Large-Network Travel Time Distribution Estimation for Ambulances

Ambulance in Georgetown. BW.

It's almost Friday, so it's almost time for the Friday Transportation Seminar. Remember that this semester the seminars and Cookie Hour are in 290 Hearst Memorial Mining Buidling. We also encourage you to follow along (and participate) with the Twitter hashtag #itsberksem

This week's Friday Seminar features Dawn Woodward from Cornell presenting, "Large-Network Travel Time Distribution Estimation for Ambulances."

We present methods to predict the time required for an ambulance to drive to the scene of an emergency. This forecast is critical for deciding how many ambulances should be deployed at a given time, where they should be stationed, and which ambulance should be dispatched to an emergency. Specifically, we predict the distribution of lights-and-sirens ambulance driving time on an arbitrary route in a road network, using automatic vehicle location data and trip information from previous ambulance trips. We train a statistical model using a computationally efficient procedure; challenges include the large size of the network and the lack of trips in the data that follow the route of interest. We demonstrate the operational impact of our methods using data from Toronto Emergency Medical Services, and discuss ongoing efforts to incorporate our methods into a software package used by ambulance services.

The Friday Seminar takes place on September 5, 2014 from 4:00-5:00 PM in 290 Hearst Memorial Mining BuildingCookie Hour immediately precedes it at 3:30 PM in the same location. (Note: Cookie Hour is not in the library!) There will be a no-host Happy Hour at LaVal's at 5:00 PM.

Institute of Transportation Studies Friday Seminar: Lessons Learned from Spatiotemporal Studies of Freeway Carpool Lanes


Late August means the end of summer is nigh, students are back, classes are in session, and it's the return of the Friday Transportation Seminars. This semester there are some changes to the seminars - Cookie Hour and the seminar will take place in the same location in 290 Hearst Memorial Mining Buidling. We also encourage you to follow along (and participate) with the Twitter hashtag #itsberksem

This week's Friday Seminar features ITS's own Professor Michael Cassidy presenting, "Lessons Learned from Spatiotemporal Studies of Freeway Carpool Lanes."

The presentation explores how the segregation of distinct vehicle classes on a roadway can improve travel conditions for all of the classes. Insights come using freeway carpool lanes as case studies. Spatiotemporal study of real sites shows (i) how the activation of a continuous-access carpool lane triggers reductions in vehicle lane-changing maneuvers, and (ii) how the reduced lane-changing can “smooth” and increase bottleneck discharge flows in a freeway’s regular lanes. Theoretical analysis predicts that, thanks to this smoothing effect, even underused carpool lanes can diminish both the people-hours and the vehicle-hours traveled on a freeway. Relevance to bus lanes is briefly discussed. Further insights come via critiques of certain practices that degrade the effectiveness of carpool lanes. Spatiotemporal traffic data reveal that a policy aimed at improving carpool-lane speeds has backfired, owing to a friction effect. The policy mandates the eviction of select fuel-efficient hybrid vehicles from carpool lanes. These evictions have caused queues to expand in regular lanes during the rush. And these expanded queues, in turn, slow vehicles in the adjacent carpool lanes. Spatiotemporal data further show that efforts to combat the friction effect by deploying limited-access carpool lanes can also backfire, because the designs for these lanes are prone to creating bottlenecks.

The Friday Seminar takes place on August 29, 2014 from 4:00-5:00 PM in 290 Hearst Memorial Mining Building. Cookie Hour immediately precedes it at 3:30 PM in the same location. (Note: Cookie Hour is not in the library!) There will be a no-host Happy Hour at LaVal's at 5:00 PM.

SB-743, CEQA, and moving away from LOS

Saturday in LA

Yesterday the Governor's Office of Planning and Research (OPR) released Updating Transportation Impacts Analysis in the CEQA Guidelines. It's the draft discussion SB-743 Environmental Quality: transit oriented infill projects, judicial review streamlining for environmental leadership development projects, and entertainment and sports center in the City of Sacramento. As the bill's name hints, the impetus for the legislation is the contentious proposed new arena for the Kings in downtown Sacramento though the effects will be felt statewide. 

Many of the concerns and questions raised by SB-743 lie in the proposed changes to litigation windows to CEQA (California Environmental Quality Act). The proposed reforms could make it easier for projects to obtain exemptions from the full CEQA project, potentially making the development of previously contested projects easier. 

From a transportation standpoint, the biggest change to CEQA is the use of level of service (LOS) in evaluating the impact of projects. Instead of relying solely on LOS to determine the significance of transportation impacts, OPR proposes:

In developing the criteria, the office shall recommend potential metrics to measure transportation impacts that may include, but are not limited to, vehicle miles traveled, vehicle miles traveled per capita, automobile trip generation rates, or automobile trips generated.

Engineering groups like Western ITE suggested using vehicle miles traveled (VMT) instead of LOS to measure impact as it focuses only on automobile congestion at the expense of other modes. So now that it looks like we're moving away from LOS, what comes next? Researchers have already begun looking at how this will affect models and traffic studies. Fehr & Peers have developed an concise website describing the impacts of SB-743

New Article: Macroscopic Fundamental Diagram and Public Transport

Changing Course in Urban Transport

A brand new article in Transportation Research Part C: Emerging Technologies examines a macroscopic fundamental diagram (MFD) and how it is applied to bi-modal urban networks. "A three-dimensional macroscopic fundamental diagram for mixed bi-modal urban networks," by (ITS alum) Nikolas Geroliminis, Nan Zheng,and Konstantinos Ampountolas investigates existence of a three-dimensional vehicle-flow MFD for bi-modal network.

Recent research has studied the existence and the properties of a macroscopic fundamental diagram (MFD) for large urban networks. The MFD should not be universally expected as high scatter or hysteresis might appear for some type of networks, like heterogeneous networks or freeways. In this paper, we investigate if aggregated relationships can describe the performance of urban bi-modal networks with buses and cars sharing the same road infrastructure and identify how this performance is influenced by the interactions between modes and the effect of bus stops. Based on simulation data, we develop a three-dimensional vehicle MFD (3D-vMFD) relating the accumulation of cars and buses, and the total circulating vehicle flow in the network. This relation experiences low scatter and can be approximated by an exponential-family function. We also propose a parsimonious model to estimate a three-dimensional passenger MFD (3D-pMFD), which provides a different perspective of the flow characteristics in bi-modal networks, by considering that buses carry more passengers. We also show that a constant Bus–Car Unit (BCU) equivalent value cannot describe the influence of buses in the system as congestion develops. We then integrate a partitioning algorithm to cluster the network into a small number of regions with similar mode composition and level of congestion. Our results show that partitioning unveils important traffic properties of flow heterogeneity in the studied network. Interactions between buses and cars are different in the partitioned regions due to higher density of buses. Building on these results, various traffic management strategies in bi-modal multi-region urban networks can then be integrated, such as redistribution of urban space among different modes, perimeter signal control with preferential treatment of buses and bus priority.

The full paper can be found here.

Friday Seminar: Travel Time Reliability and Network Traffic Performance

Travel Times

This week's TRANSOC Friday Seminar features Professor Hani Mahmassani of Northwestern University presenting "Travel Time Reliability and Network Traffic Performance: Selected Highlights from Recent Research"

Reliability of travel time in traffic networks is affected by a variety of factors,some external (e.g. demand surges, weather) and others inherent to the behavior of the traffic stream, reflecting complex dynamics among interacting agents. Yet remarkably simple collective effects emerge when examining the relation between the standard deviation of the trip time per unit distance to the corresponding mean at the network level. We examine this relation for several networks using both simulated and actual data from vehicle probes. We connect this variance to other traffic variables defined at the network level, providing a simple characterization of travel time reliability as a function of density. We consider within-day and day-to-day variability and propose a compound gamma model to capture overall variation. To evaluate the reliability implications of different transportation options and operational strategies using simulation tools, a scenario-based approach is proposed and demonstrated.

The seminar takes place this Friday, February 21, 2014 from 4-5 PM in 534 Davis. Cookie Hour commences at 3:30 in the library.

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