At midnight July 1 2013, after failed negotiations between BART and its two main unions, BART workers went on strike. The strike has disrupted transportation throughout much of the Bay Area-  increasing commute times and traffic congestion. Many commuters are turning to the ferries, casual carpool, and rideshare. The more adventurous have opted for helicopters or yachts. While there has been the predicted mix of frustration, criticism, and selfpromotion on Twitter via #BARTstrike, it's still too early to gague the real impact of the strike on transportation. Some projections estimate the econmic impact to be $73 million a day as well as 16 million pounds of carbon. Some clues might be gleaned from the recently published, Subways, Strikes, and Slowdowns: The Impacts of Public Transportation on Traffic Congestion. Using data from the 2003 transit worker strike in Los Angeles, researchers show that transit relieves traffic congestion

Access Across America: How accessible are the jobs?

This week University of Minnesota's CTS issued a report about accessibility to job that includes an interactive map. Access Across America

Access Across America, a study by David Levinson, the R.P. Braun/CTS Chair in Transportation Engineering at the University of Minnesota, goes beyond congestion rankings to focus on accessibility: a measure that examines both land use and the transportation system. The study is the first systematic comparison of trends in accessibility to jobs by car within the U.S. By comparing accessibility to jobs by automobile during the morning peak period for 51 metropolitan areas, the study tells us which cities are performing well in terms of accessibility and which have seen the greatest change.

The full report can be found here. And here's the data!California is well represented with Los Angeles (1), SF-Oakland (2), and San Jose (6) all in the Top Ten.

Megacommuters: Travel time and income.

405 Freeway Los Angeles

Earlier this month the Census Bureau released the new American Community Survey (ACS). One of the figures they highlighted was the rise of the "megacommuters".

About 8.1 percent of U.S. workers have commutes of 60 minutes or longer, 4.3 percent work from home, and nearly 600,000 full-time workers had "megacommutes" of at least 90 minutes and 50 miles. The average one-way daily commute for workers across the country is 25.5 minutes, and one in four commuters leave their county to work.

The Bay Area is the nation's megacommuter capital with 2.6 percent of the full-time workers in the region enduring megacommutes. 

These statistics are interesting and relate to a new paper from University of Minnesota. Published in the March 2013 issue of Transportation, "Selfishness and altruism in the distribution of travel time and income" by Nebiyou Tilahun and David Levinson report the results of a Stated Preference experiment comparing choice income and travel time. 

Does distance matter? How does where you live and work affect happiness?

Divisadero Parklet - Bike Parking - San Francisco

A new article from Transportation Research A: Policy and Practice investigates travel behavior related to where people live and work (for those who can't telecommute). "Does distance matter? Exploring the links among values, motivations, home location, and satisfaction in walking trips" looks at traveler motivations and levels of satisfaction. They also suggest a new conceptional model for walking behavior. The research will help develop a more robust understanding of travel behavior and choice. You can find the whole article here

The State of Congestion: TTI releases the 2012 Urban Mobility Report


Recently the Texas A&M Transportation Institute released the 2012 Urban Mobility Report. This year's model relies upon a new methodology and expands the coverage, and you can download the data for your city.   The changes give a better picture of issues related to traffic congestion across the United States, as well as historic trends from 1982 to present, though some question if TTI underestimates congestion back them. 

Bay Area Traffic Decoded: What cell phone and GPS data reveals about traffic patterns

580 and I80 Traffic Jam

A new article from researchers at MIT and UC Berkeley uses data from cell phones and GPS to track traffic patterns. "Understanding Road Usage Patterns in Urban Areas" from December's Scientific Reports assess how drivers from certain areas effect the whole network. 

 We find that the major usage of each road segment can be traced to its own - surprisingly few - driver sources. Based on this finding we propose a network of road usage by defining a bipartite network framework, demonstrating that in contrast to traditional approaches, which define road importance solely by topological measures, the role of a road segment depends on both: its betweeness and its degree in the road usage network. Moreover, our ability to pinpoint the few driver sources contributing to the major traffic flow allows us to create a strategy that achieves a significant reduction of the travel time across the entire road system, compared to a benchmark approach.

Drivers from Sanjose, Hayward, Dublin, San Rafel and San Ramon often find themselves stuck in the worst traffic. Could more metering be the answer?

Friday Seminar - Vikash Gayah on The Aggregate Effect of Turns on Urban Traffic Networks

overland ave traffic

This week’s Friday TRANSOC Seminar has Vikash Gayah, Ph.D. candidate, University of California, Berkeley, presenting “The Aggregate Effect of Turns on Urban Traffic Networks.” 

This research creates and uses macroscopic traffic models to describe the aggregate behavior of vehicles on urban street networks. Insights gained from these models can then be used to design network-wide policies that may increase the ability of these networks to serve vehicle-trips. In particular, this work focuses on the turning maneuvers that exist in networks with multiple routes. The presence of multiple routes and turning maneuvers are found to have two effects on aggregate vehicle behavior: 1) they cause unstable and inefficient behavior when a network is congested; and, 2) they may reduce maximum vehicle flows across the network. Fortunately, this work finds that limiting the rate at which vehicles are allowed to enter a network and providing drivers with real-time information on current traffic conditions can help mitigate the first effect and allow the network to operate more efficiently. It is also found that the second effect may not always be harmful—lower network flows do not necessarily result in decreased network efficiency if the lower flows are accompanied by more direct vehicle routing. In fact, two-way networks, which accommodate conflicting left-turns and result in lower maximum vehicle flows than one-way networks, are found to serve trips at a higher rate because drivers travel shorter distances on average. Thus, in many cities, maximum network efficiency can be improved by converting one-way streets to two-way operation.

The seminar will take place at 4:00 PM in534 Davis Hall. Please join us for a TRANSOC-sponsored Cookie Hour in the ITS Library at 3:30 PM.

Friday Seminar - Nikolas Geroliminis on Traffic Systems

A (small) part of traffic-1

Today’s TRANSOC Friday Seminar has Nikolas Geroliminis, PhD., Assistant Professor, Urban Transport Systems Laboratory, École Polytechnique Fédérale de Lausanne (EPFL) presenting “The M6 of traffic systems: Macroscopic Modeling, Monitoring and Management of Multimodal Mobility.”

As more people and transport modes compete for limited urban space to travel, there is a need to understand how this space is used for transportation and how it can be managed to avoid traffic congestion. Our research seeks to shed some light in the modeling, planning and management of traffic flow for overcrowded cities with multimodal transport. We develop methodologies to model and understand the collective behavior for different types of multi‐modal systems, with emphasis in conflicts for the same road space (e.g. mixed traffic of buses and cars). The goal is to develop optimization tools on how to distribute city road space to multiple modes and to understand the level of accessibility for cities of different structures. We also investigate what type of real-time active traffic management schemes (congestion pricing, vehicle restriction, large scale traffic signal control) can improve mobility measures in a city. Until now traffic control systems in urban areas are locally programmed with little control over the impact of a micro-scale response to the macro-scale level. We build a hierarchical feedback control network of multiple levels. The validation of the modeling methodologies and the traffic management schemes are conducted in various and complex city structures scenarios using data from field experiments advanced micro-simulations.

The seminar will take place today 4:00 PM in 406 Davis Hall. Please join us for a TRANSOC-sponsored Cookie Hour in the ITS Library at 3:30 PM.

Friday Seminar - Ilgin Guler on Strategies for Sharing Bottleneck Capacity among Buses and Cars

let photo speak...

Tomorrow's TRANSOC Friday Seminar features Ph.D. candidate Ilgin Guler presenting, "Strategies for Sharing Bottleneck Capacity among Buses and Cars."

Buses that operate in mixed traffic can be impeded by car congestion, leading to unreliable and slow bus service. Conversely, buses that frequently stop to serve passengers can interfere with the movement of cars. To address these issues, exclusive bus lanes have often been used to segregate buses from other traffic. These exclusive bus lanes provide a means for buses to bypass car queues, thereby increasing bus speed and potentially decreasing the total person hours travelled on a network. In urban settings exclusive bus lanes are typically deployed by converting an existing general purpose lane to bus use only. However, in cases where bus flow is low, these lane conversions can increase the queuing and delays to cars. The problem is particularly acute at roadways bottlenecks, since cars now discharge from one less lane, even when the bus lane is unoccupied.

This research examines strategies for judiciously inserting cars between buses in ways that minimize the losses in a bottleneck’s car carrying capacity when bus demand is low. The idea entails sharing lanes among buses and cars in the vicinities of critical bottlenecks; and to have these shared lanes augment exclusive bus lanes that are deployed elsewhere throughout the network. The specific type of sharing strategy to be used near any given bottleneck would depend upon its operating conditions. In all cases the goal is to prioritize bus travel while minimizing the additional delays that this prioritization imparts to cars. Analysis unveils the ranges of bus demands for which the shared‑lane strategies are superior to ordinary lane conversions. We find that the shared-lane strategies have merit in many instances. Implementing these strategies for a real-world case study in Amman, Jordan produces promising outcomes: simulation analysis indicates that the delay savings to cars brought by the lane–sharing strategies are considerable. The proposed ideas can help increase the political acceptability of bus priority systems and promote public transportation in cities of various sizes.

The Seminar will be from 4-5pm in 406 Davis Hall. There will be no cookie hour precedding it this week, so you'll need to sort out your sugar fix some other way. 

Friday Seminar -Kitae Jang on Traffic Interactions in Freeways with Carpool Lanes

carpool lane

This Friday's TRANSOC Seminar features Kitae Jang, Ph.D. Candidate, University of California, Berkeley, presenting on "Traffic Interactions in Freeways with Carpool Lanes."

The study is concerned with the vehicular interactions that arise when carpool and regular vehicles are segregated in their own lanes. Real data show that reserving a lane for carpools on congested freeways induces a smoothing effect that is characterized by significantly higher bottleneck discharge flows (capacities) in adjacent regular-use lanes.  Thanks to this smoothing effect, we find in many cases that the carpool lanes – even when underused themselves – can benefit travelers in the regular lanes.  Ironically, the regular-use lanes are often damaging to the carpool-lane travelers. We find that the vehicle speeds in a carpool lane are negatively influenced by both growing use of that lane and diminishing vehicle speeds in the adjacent regular-use lane.  The findings do not bode well for a new US regulation stipulating that most classes of Low-Emitting Vehicles (LEVs) are to vacate slow-moving carpool lanes.  Analysis shows that relegating some or all of these vehicles to regular-use lanes can significantly add to regular-lane congestion; and that despite the reduced use of the carpool lanes this, in turn, can also reduce the speeds of those vehicles that continue to use the carpool lanes.  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.

The seminar will take place from 4-5 pm in 406 Davis on November 18. Please come to TRANSOC's Cookie Hour preceeding the seminar at 3:30 pm in the library.

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