Cross-cutting Issues

Loop detectors have been widely used to estimate travel time delay. One
implicit assumption about the estimation is that traffic flow is ‘stationary’. Based on this
assumption, the point data collected by loop detectors at different locations could be
interpolated or extrapolated to estimate travel time delay for segments between adjacent
loop detectors. This assumption is not quite valid when vehicle speeds fluctuate spatially
and temporally. It is desirable to examine and understand the accuracy level of such
travel time delay estimation methodology in real-world situations. The purpose of this
paper is to present an empirical analysis to explicitly illustrate the accuracy level of travel
time delay estimated using loop detectors. Travel time delay obtained from eight freeway
segments under various combinations of reference speeds, data aggregation intervals, and
loop detector spacings are studied and compared with true delays determined using
vehicle trajectory information. For all the eight freeway segments evaluated, it was
found that the mean absolute percentage errors of delay estimation are consistently less
than 7% when delay is defined using a reference speed higher than 60 mph (96 kmph).
Higher mean absolute percentage error was observed for lower reference speeds, longer
detector spacings and turbulent traffic situations, such as traffic incidents. Adopting
higher reference speed, say 60 mph (96 kmph), longer aggregation interval, say 300-
second, and shorter loop detector spacing, say 1000-ft. (305 m), helps produce lower
mean absolute percentage error in loop detector-estimated travel time delay.

California Department of Transportation

Villanova University

Presented at the 12th World Congress on Intelligent Transport Systems, November 6-10, 2005, San Francisco, California

This study begins to examine the potential demand for ITS technologies in Minnesota’s populace, both in the Twin Cities and statewide, with a focus on those attracted to services that do not require owning a single occupant vehicle to serve as the primary mode of transportation. The primary objective is to better understand how the needs of travelers are changing and how
ITS can be used to provide better transportation services to meet those changing needs.  
The research identified three populations that would benefit from ITS solutions. As travel
behavior has become much more diverse, corresponding groups of diverse travelers are
emerging. Car sharing, flexible transit and telecommuting / Advanced Traveler Information
Systems (ATIS) are ITS solutions for these diverse groups that can be tailored to meet the
assorted travel needs of these groups. The research problem is to identify the nature of the gap between the emerging needs and existing services, and to propose ways to use technology to bridge the gap, both in terms of providing better transportation options and in reducing the cost of these options.

University of Minnesota

Presented at the ITS America Annual Conference and Exposition, April 26 - 28, 2004 San Antonio, Texas

Electronic Toll Collection (ETC) is one of the clear success stories for intelligent transportation systems. To date, focus has been on the ability of these systems to process two to four times more vehicles than an automatic coin machine and collect tolls at highway speeds. However, ETC has the potential to revolutionize the toll collection industry in an additional manner – through the collection of time-of-day or congestion-based variable tolls.

This paper first examines how ETC in Lee County, Florida, is being used to charge tolls that vary by time of day. Variable tolling/pricing has been operational since August 1998 and has successfully shifted some peak-period traffic to off-peak times. The paper then uses responses from a recent revealed-choice telephone survey to examine user participation and response to both ETC and the variable tolling program. ETC has made a real impact on Lee County traffic, not just through improved toll collection efficiency, but also through the innovative time-of-day variable tolls.

University of South Florida - Center for Urban Transportation Research

Presented at the 10th ITS Annual Conference and Exposition, May 1-4, 2000 Boston, MA

Bottlenecks are key features of any freeway system and their impacts are of increasing
importance as congestion worsens in urban areas. In Oregon, a freeway data archive known
as PORTAL records measured count, occupancy, and speed data from over 600 locations at
20-second intervals. This archive has enabled development of online freeway performance
and reliability analysis tools. This paper describes the development of an automated tool for
identifying recurrent freeway bottlenecks using historical data within the PORTAL
framework. Efforts have focused on the selection of optimal variables to enable identification
and display of active bottleneck features using graphical tools. This research also aims to
detect bottleneck activation in real time and to expand the use of reliability techniques.
Ultimately the results of this research will aid in the prioritization of freeway improvements.

Portland State University

Presented at the 15th World Congress on Intelligent Transport Systems, November 16-20, 2008, New York, New York

This paper presents a case study of a comprehensive, innovative approach used by the
Missouri Department of Transportation (MoDOT), through its traveler information
partnership with NAVTEQ/Nokia and its NAVTEQ Traffic.com™ solutions, to use
advanced traveler information services to reduce recurring congestion caused by the
closure of I-64 in St. Louis, Missouri in the United States. The innovative approach
included installing additional traffic sensors to increase real-time data, using probe data
to provide additional coverage, staffing the NAVTEQ Traffic operations centers 24/7,
placing NAVTEQ Traffic staff in the MoDOT Gateway Guide operations center,
providing NAVTEQ Traffic.com511™ (ATIS) services by phone, web and email, and
disseminating NAVTEQ Traffic to XM satellite radio, local TV and radio stations.

Traffic.com, Inc

Missouri DOT, St. Louis Region

Presented at the ITS America Annual Conference and Exposition, November 16-20, 2008, New York, New York