Lesson

Provide ITS data at different aggregation levels as well as unaggregated data to satisfy diverse user needs.

National experience with ITS data archiving, sharing and usage.


5/1/2002
Madison,Wisconsin,United States


Background (Show)

Lesson Learned

Many stakeholders including planning, operations, and research staff, use different levels of aggregation. They are interested in performing similar analyses at different aggregation levels. One solution to the need for different levels of aggregation might be to save the basic aggregated data for current needs and use innovative archiving capabilities to provide advanced data users with access to raw, unaggregated data. There does not appear to be a least common denominator of data aggregation that is significantly favored, other than simply raw, unaggregated data.

Take into account the various users' needs:
  • Transportation planners require the most aggregated data. They require data aggregated for periods of 15 minutes or more. They often require data for various segments and time periods.
  • Traffic management operators often require data that are less aggregated (aggregation levels of 1, 5, or 15 minutes) than the transportation planners. The incident detection algorithm development requires data at intervals of less than 1 minute while typical applications evaluating highway capacity or ramp metering strategies may utilize data at the 5-minute aggregation level.
  • Transportation researchers typically desire the least aggregated data of all stakeholders. They will often use data in the least aggregated form available (i.e. data over a 20-second period, or individual probe vehicle data). Advanced data users such as transportation researchers generally have a significant amount of computing power and data manipulation tools at their disposal to assist them in analyzing large data sets.

For example, the research performed at the Institute of Transportation Studies (ITS) at the University of California at Berkeley has used unaggregated ITS data supplied by loop detectors to evaluate traffic features of freeway bottlenecks on two freeways in Toronto, Ontario, Canada. Speed, occupancy, and volume data were collected every 30 seconds along the Queen Elizabeth Way and the same data were collected every 20 seconds along the Gardiner Expressway.

Identifying which aggregation levels are necessary for different applications is indispensable. Different uses of ITS data require different levels of detail. Design and operational applications commonly require detailed data for shorter roadway sections and time intervals. Planning applications require the most aggregated data and commonly require historical data over extended sections of roadway and periods of time. Aggregating data at the right level is important because it helps transportation planners, traffic management operators, and transportation researchers to more effectively conduct the analyses and answer their questions of interest.


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Source

A Literature and Best Practices Scan: ITS Data Management and Archiving

Author: Henry X. Liu, Rachel He, Yang Tao, and Bin Ran

Published By: University of Wisconsin

Source Date: 5/1/2002

Other Reference Number: 0092-02-11

URL: http://on.dot.wi.gov/wisdotresearch/database/reports/02-11itsdata-f.pdf

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Lesson Contacts

Lesson Analyst:

Jane Lappin
Volpe National Transportation Systems Center
617-494-3692
jane.lappin@volpe.dot.gov


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Lesson ID: 2006-00252