Unintended Consequences: Booting Hybrids from HOV Lanes Slows Traffic

 Hybrid car in the carpool lane, Institute of Transportation Studies, University of California, Berkeley

This past July, the California Clean Air Stickers for HOV Lanes program ended for hybrids. What was the effect of this change? How did it affect traffic flow and congestion? That question was investigated by ITS researchers Prof. Michael Cassidy and Kitae Jang, of the Volvo Center.  Their new ITS report, Dual Influences on Vehicle Speeds in Special-Use Lanes and Policy Implications, analysed traffic data and used models to calculate the impact of the added low-emissions vehicles on the other lanes. Cassidy told the Berkeley Newscenter:

“Our results show that everybody is worse off with the program’s ending,” said Cassidy. “Drivers of low-emission vehicles are worse off, drivers in the regular lanes are worse off, and drivers in the carpool lanes are worse off. Nobody wins.”

...

“As vehicles move out of the carpool lane and into a regular lane, they have to slow down to match the speed of the congested lane,” explained Jang. “Likewise, as cars from a slow-moving regular lane try to slip into a carpool lane, they can take time to pick up speed, which also slows down the carpool lane vehicles.”

The paper was also discussed by the New York Times, USA Today, and the LA Times

Get Down with Bicycle Safety

Avid readers know that this week was International Walk to School Day in the USA, part of the Safe Routes to Schools program. Bicycle safety has always been an important component of safe routes to schools, even way back in the 80s. Here's is an old school jam from an after school special circa 1989. You dig?

Word. Though safe bicycling is still important, even for adults. Listen to this rhyme king tell you all about the need for proper illumination. 

Stay safe out there. 

Friday Seminar: Mazyar Zeinali on Commercial Aviation and Climate Change

Airbus A380-800

This week's TRANSOC Friday Seminar is Mazyar Zeinali from the International Council on Clean Transportation presenting "Commercial Aviation and Climate Change: The Role of Technology."

The environmental impact of aviation has been of concern for several decades including specific concerns such as local air quality, impacts on Earth's protective ozone layer, and aircraft induced cloudiness. However, with the 1999 seminal publication by the Intergovernmental Panel on Climate Change (IPCC) entitled 'Aviation and the Global Atmosphere', significant concern has arisen both in aviation climate change impact and mitigation possibilities. To quantify expected return from future technology implementation (near to mid term), the International Civil Aviation Organizational (ICAO) commissioned and published a study conducted by a panel of independent experts (IEs). The IE technology scenarios included returns under typical/continuation of current business-as-usual practices and also accelerated implementation under added future regulatory pressure. The ICCT was a contributing organization to this ICAO study and Dr. Zeinali will present his findings and interpretations for specific technological packages envisioned by the panel and efficiency gains from implementing technology in tighter aircraft designs, better matching operational norms and patterns.

The seminar will take place October 7 from 4-5 PM in 406 Davis Hall. Cookie Hour will be at 3:30, as usual, in the library. 

International Walk to School Day and Safe Routes

going to school

Today International Walk to School Day in the USA. Did you know that? You probably did. Everyday can be walk to school day through the work of the Safe Routes to School program, a multidisciplinary coalition with members from transportation, public health, and housing. Their report, Getting Students Active through Safe Routes to School: Policies and Action Steps for Education Policymakers and Professionals, contains information about how schools can implementa a safe routes program and things to consider. The TransForm report, Bringing Safe Routes to Scale, which focuses on the Bay Area. SafeTREC researchers Jill Cooper and Tracy McMillan published a report last year that evaluated 10 low income schools

 

Petaluma Going Yellow for Left Turns

left turn signal

Yesterday the Press Democrat reported on Petaluma replacing the "left on green" signals with flashing yellow lights

The city will replace all or some of the protected-permissive signals at 26 intersections throughout town, while allowing a few to remain as is.

Some will include a signal new to California and what may be a first for Sonoma County — the flashing yellow left-turn arrow.

Petaluma Boulevard North at Magnolia Avenue/Payran Street had a “higher than expected collision experience involving left-turning vehicles,” Zimmer said.

In all four directions, the protected-permissive signals will be replaced with protected left-turn phasing, meaning left-turn drivers will see a progression of green, yellow and red arrows.

Then, once the intersection is cleared, a flashing yellow arrow will light, alerting drivers that they may proceed with caution with a left turn when oncoming traffic is clear.

The 2009 MUTCD includes languange about flahsing yellows for left turns (4D.17-4D.20). The topic is also discussed in NCHRP Report 493: Evaluation of Traffic Signal Displays for Protected/Permissive Left-Turn Control. While Petaluma is the first city in California to implement this sort of signal, it has been catching on across the nation. Next year, two different research projects investigating the impacts of flashing yellows on protected left turns should be completed. One is Evaluation of Flashing Yellow Arrows (FYA) for Protected/Permissive Left Turn (PPLT) Control from Bradley University for the Illinois DOT. The other is Field Study of Driver Behavior at Flashing Yellow Arrow vs Green Ball Permitted Left-Turn Indications by CTS of the University of Minnesota for the ITS JPO of RITA

 (Hat tip to @thedotreport)

 

Raising Speed Limits: Impact on Safety?

Motorway Three

Today the state of Maine raised its speed limit from 65 to 75 mph. Across the Atlantic, today it was also announced that the British government wants to raise the speed limit to 80 mph. Proponents argue that increasing the speed limit will propmote economic growth through reducing congestion, which was touched upon in the TTI report "Speed Harmonization and Peak-period Shoulder Use to Manage Urban Freeway Congestion." Opponents are concerned about the implications on traffic safety. Purdue's Fred Mannering wrote about the relationship between safet and speed in his 2009 article, "An empirical analysis of driver perceptions of the relationship between speed limits and safety." In the report, "Long-Term Speed Compliance and Safety Impacts of Rational Speed Limits," researchers from University of Virginia and VTRC found that increased speed limits along with coordinated education and enforcement can be safe.

 

Friday Seminar - Paul Waddell on Pedestrian Scale in Transportation Models

pedestrian crossing

This week's TRANSOC Friday Seminar feature Paul Waddell from the Department of City & Regional Planning at Cal. He will be present, "Addressing the Challenge of Representing the Pedestrian Sclae in Transportation Models". 

Transportation models have used zonal geography and coarse representations of the transport network to represent the spatial environment for trip origins, destinations and routes.  But the coarseness of the zonal geography and transport networks is inconsistent with the level of detail needed to represent walking and bicycling adequately.  This also has implications for the representation of transit, which is so dependent on walk access at origin and destination of transit trips.  This talk addresses recent work underway as part of projects funded by NSF and MTC, to develop an analytic and visualization capability at a level of detail of parcels and local streets.  Preliminary development of an integrated database, model system, and visualization platform yields early insight into strategies to more fully represent pedestrians and bicyclists within land use and transportation models and planning.

The seminar will be on September 30th, from 4-5 pm in 406 Davis Hall. Cookie Hour preceeding, as usual, in the library at 3:30 pm. See you there!

2011 Urban Mobility Report out now!

San Francisco - New Montgomery St.

The 2011 Urban Mobility Report has been released with week from the University Transportation Center for Mobility, a part of the Texas Transportation Insitute at Texas A&M. 

The 2011 Urban Mobility Report builds on previous Urban Mobility Reports with an improved methodology and expanded coverage of the nation’s urban congestion problem and solutions. The links below provide information on long-term congestion trends, the most recent congestion comparisons and a description of many congestion improvement strategies. All of the statistics have been recalculated with the new method to provide a consistent picture of the congestion challenge. As with previous methodology improvements, readers, writers and analysts are cautioned against using congestion data from the 2010 Report. All of the measures, plus a few more, have been updated and included in this report.

You can download the full report here. They also include summary tables for quick analysis and you can access congestion data for your city and even download the data for all 101 cities. A wealth of information to use in your research. Good stuff!

Friday Seminar - Marta C. Gonzalez on Characterizing Urban Road Usage Patterns

Traffic I Missed

This week's Friday Seminar is MIT's Marta C. Gonzalez presenting "Charactericing Urban Road Usage Patterns with a New Metric." The seminar will take place from 4-5 PM in 506 Davis Hall on 23 September. 

Mobility data from half million anonymous mobile phone users are used for this presentation to study the road usage patterns in the Bay Area. Using this mobility data based on our modeling framework each trip’s route is predicted. Surprisingly, it is found that on average 60% of the vehicles passing through a road segment come from 1% of its drivers’ home locations, hinting to high predictability of the vehicle sources. To quantify the heterogeneous traffic contributions of the vehicle sources we use the Gini coefficient and find that a road segment’s Gini coefficient is poorly correlated with its betweenness, traffic volume, and volume over capacity, suggesting that Gini coefficient is a new metric on top of the traditional measures, quantifying road usage patterns in the perspective of drivers’ demographic distribution. Finally, based on the road usage patterns, we find an efficient strategy to mitigate traffic congestion through a tiny decrease of car usage rates in a few targeted neighborhoods.

Don't forget about Cookie Hour in the library at 3:30! See you then.

Special Wednesday Seminar! Lin Zhang discusses Crowd-sourced Mobile Urban Sensing

taxis

This afternoon, Spetember 21,  there will be a special Wednesday Seminar. From 2-3 PM in 406 Davis Hall, Lin Zhang of Tsinghua University will present "Crowd-sourced Mobile Urban Sensing".

Wide area urban sensing is a topic of interest both within industry and academia, as well as a technique urgently needed by both city governments and urban residents.  In today’s rapidly urbanizing world, the urban sensing system provides up-to-date, complete and detailed observations of the climate, environment, traffic, and population of a city, all information which can aid government officials in the decision-making process.  The urban sensing system is also a frontier of Internet development, enabling cyber space to sense the ambient environments in which it is embedded.  However, there are two major challenges to urban sensing: communication capacity and sensing capability. 

This presentation will introduce a taxi-cab based mobile sensor system that was designed for wide-area urban sensing purposes.  The presented system addresses both of the aforementioned challenges as well as  considerations of economic and technical feasibility.  The system crowd-sources the sensing tasks to a group of taxi cabs roaming the city, and uses the store-carry-and-forward mechanism to collect and send sensory data to the data center for processing.  Compared to a static, dedicated sensor network, the system enjoys extremely low deployment costs with fairly strong coverage and performance.  The presentation will also describe the details of the system design, including the wireless channel measurement, an energy efficient neighbor discovery method, a utility-based routing protocol for data delivery, and a compressive sensing field recovery algorithm that exploits the sparsity of the physical field in order to reduce the volume of the required sensing data.  The presentation closes with a a discussion of future deployment plans and research directions for the system.

 

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