Traffic Engineering

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.

Complete Streets

 From the Fall 2009 Tech Transfer Newsletter


  • National Complete Streets Coalition
    The National Complete Streets Coalition is comprised of planning organizations, advocacy groups, consultants, and local governments interested in the implementation of the Complete Streets concept nationwide. They provide information and news about Complete Streets initiatives, as well as resources to help people host their own community workshops about Complete Streets. The website also tracks pertinent federal policies including American Recovery and Reinvestment Act of 2009 (ARRA) projects and funds.
  • Complete Streets in California
    California Department of Transportation - Division of Transportation Planning
    The main portal for information about Caltrans' Complete Streets projects and guidelines, including implementation of Deputy Directive 64.
  • Complete Streets: Talking Points
    Planning for Healthy Spaces - Public Health Law and Policy
    A brief introduction to the Complete Streets model and how different aspects of the plan can improve the health and safety of different user groups, such as pedestrians or bicyclists.

Reports, Articles and Conference Proceedings

  • Complete Streets: We Can Get There from Here
    John LaPlante and Barbara McCann, ITE Journal, v.78, n.5, May 2008, pp. 24-28
    Provides an introduction and overview of the Complete Streets movement, as well as some points to consider before implementing changes in your location.
  • Retrofitting Urban Arterials into Complete Streets [PDF, 0.3 M]
    John LaPlante, 3rd Urban Street Symposium: Uptown, Downtown, or Small Town: Designing Urban Streets That Work, 2007
    Examines different issues related to retrofitting existing arterials into Complete Streets, addressing the tension inherent between the need for traffic capacity and speed and making streets safe for bicyclists and pedestrians as well.
  • Brave New Nonmotorized World
    Jay Walljasper, Planning, v. 74, n.11, December 2008, pp. 20-23
    Provides an analysis of how bicycling and pedestrian retrofits and improvements in European cities provide case studies and examples for similar projects in American cities.
  • Planning Complete Streets for an Aging America [PDF, 33.2 M]
    Jana Lynot et al., AARP Public Policy Institute, 2009
    Discusses how the Complete Streets agenda impacts and benefits mobility for the aging population. Interdisciplinary research examines how the Complete Streets program will affect older drivers and pedestrians, examining design recommendations to improve safety for travelers of any age.


Here are other organizations that are interested in and working toward implementing Complete Streets nationwide.


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