April 9, 2008.
California Office of Traffic Safety Summit
San Francisco, CA.
May 19, 2009
University of Minnesota Center for Transportation Studies
Bloomington, MN
June 23, 2009
Driving Assessment 2009
Big Sky, Montana
June 26, 2009
PRI World Congress
Rotterdam, The Netherlands
June 27, 2009
Day of Architecture
Utrecht, The Netherlands
July 13, 2009
Association of Transportation Safety Information Professionals (ATSIP)
Phoenix, AZ.
August 12-14
Texas Department of Transportation “Save a Life Summit”
San Antonio, Texas
September 2, 2009
Governors Highway Safety Association Annual Meeting
Savannah, Georgia
September 11, 2009
Oregon Transportation Summit
Portland, Oregon
October 8
Honda R&D Americas
Raymond, Ohio
October 10-11
INFORMS Roundtable
San Diego, CA
October 21, 2009
California State University-San Bernardino, Leonard Transportation Center
San Bernardino, CA
November 5
Southern New England Planning Association Planning Conference
Uncasville, Connecticut
January 6
Texas Transportation Forum
Austin, TX
January 19
Yale University
(with Donald Shoup; details to come)
Monday, February 22
Yale University School of Architecture
Eero Saarinen Lecture
Friday, March 19
University of Delaware
Delaware Center for Transportation
April 5-7
University of Utah
Salt Lake City
McMurrin Lectureship
April 19
International Bridge, Tunnel and Turnpike Association (Organization Management Workshop)
Austin, Texas
Monday, April 26
Edmonton Traffic Safety Conference
Edmonton, Canada
Monday, June 7
Canadian Association of Road Safety Professionals
Niagara Falls, Ontario
Wednesday, July 6
Fondo de Prevención Vial
Bogotá, Colombia
Tuesday, August 31
Royal Automobile Club
Perth, Australia
Wednesday, September 1
Australasian Road Safety Conference
Canberra, Australia
Wednesday, September 22
Wisconsin Department of Transportation’s
Traffic Incident Management Enhancement Program
Statewide Conference
Wisconsin Dells, WI
Wednesday, October 20
Rutgers University
Center for Advanced Infrastructure and Transportation
Piscataway, NJ
Tuesday, March 8, 2011
Ontario Injury Prevention Resource Centre
Injury Prevention Forum
Toronto
Monday, May 2
Idaho Public Driver Education Conference
Boise, Idaho
Tuesday, June 2, 2011
California Association of Cities
Costa Mesa, California
Sunday, August 21, 2011
American Association of Motor Vehicle Administrators
Milwaukee, Wisconsin
Wednesday, October 26, 2011
Attitudes: Iniciativa Social de Audi
Madrid, Spain
April 16, 2012
Institute for Sensible Transport Seminar
Gardens Theatre, QUT
Brisbane, Australia
April 17, 2012
Institute for Sensible Transport Seminar
Centennial Plaza, Sydney
Sydney, Australia
April 19, 2012
Institute for Sensible Transport Seminar
Melbourne Town Hall
Melbourne, Australia
January 30, 2013
University of Minnesota City Engineers Association Meeting
Minneapolis, MN
January 31, 2013
Metropolis and Mobile Life
School of Architecture, University of Toronto
February 22, 2013
ISL Engineering
Edmonton, Canada
March 1, 2013
Australian Road Summit
Melbourne, Australia
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| 
January 11th, 2009 at 10:14 am
A simple way to explain this is that people all use some form of the equation for stopping distance we learned in drivers ed to allow safe following distance to react to traffic changes.
distance = velocity * reaction time + braking coefficient * velocity^2 + some constant
Reaction distance increases linearly with speed, slowing distance increases quadratically. Once the speed is reached where reaction distance is equal to stopping distance, more speed requires much more stopping distance. So at high speeds, more space is needed to follow safely. At 45mph, much less space is needed than at 70, so more cars fit onto the roads.
Also, once capacity for a given speed has been reached, when new cars enter the system, traffic must slow down to make space. This is true whether traffic is flowing above or below the ~45mph threshold. So preventing new cars from entering the system allows traffic to flow at a more efficient speed.
Interestingly, the 45mph speed is very near the optimal speed for fuel efficiency. 55mph gets optimal fuel efficiency, but there is little difference between 55 and 45mph efficiency.
Below 55mph, faster is more fuel efficient. This is probably a big part of why high gas prices cause fuel efficiency to go down, as has been happening for several years. Despite less driving and more efficient vehicles being bought.
People mistakenly think slow is more fuel efficient, both in acceleration and speed. Accelerating quickly, but smoothly, is more efficient than accelerating slowly. And faster is more efficient except for freeway speeds above 55mph.
When people bring this slow is efficient mentality to the surface streets, congestion at bottlenecks compounds this problem.