Collecting intersection data through their adaptive signal control system has helped Bellevue, Washington develop a better understanding of traffic patterns in the city and adjust timing plans accordingly.
Other benefits of this data collection for Bellevue include improved customer service and free research on their arterials performed by a local university.


United States

NCHRP Synthesis 447: Active Traffic Management for Arterials

Summary Information

This synthesis documents the state of the practice associated with designing, implementing, and operating active traffic management (ATM) on arterials. Information for this synthesis was gathered through a literature review of advanced ATM methods for arterials and in-depth telephone interviews of agencies selected through a screening interview. The study has provided information on strategies used to actively manage traffic and congestion on arterials; situations and operating conditions in which ATM strategies have been successfully and unsuccessfully deployed on arterials; and system and technology requirements associated with implementing the strategies.

Adaptive Signal Control System Collecting Arterial Intersection Data

Bellevue, Washington uses more than 500 inductive loop detectors and an adaptive signal control system at 110 signalized intersections to collect high fidelity arterial traffic data, which is then published to an FTP site. Bellevue is focused on improving the accessibility of this data, which has included hiring an intern to write software to improve the accessibility of the data outputs. As accessibility improves and automated systems are verified for accuracy, plans are to retire the older, more time and labor intensive manual methods of data collection.

Bellevue contended with both technical and institutional constraints in implementing their arterial data collection network. Technical constraints were based primarily around having an older system that needed upgrades. The original system could only report eight loops of data for an entire intersection, which was not enough for full intersection coverage. The new adaptive system implemented by Bellevue can report as many as 24 loops of data. This allows the city to have lane-by-lane information for each intersection approach, giving them turn movement counts.


There were a number of positive outcomes from implementing the arterial data collection efforts in Bellevue:
  • Higher quality and more frequent collection of data on intersection operations, enabling increased responsiveness to complaints.
  • Because they had large quantities of data available, a lot of research has been done on the arterials in Bellevue at no cost to the city by students, including those at nearby University of Washington.
  • The city developed a better understanding of how the controllers collect and report data.
  • The city developed a better understanding of the traffic patterns in the city. For example, the data collected through the automated system enabled the city to see this second peak and they could make sure they accommodated it rather than starting to transition to a midday signal timing plan earlier in the morning. Microsoft, for example, has a more flexible start time than do other companies, so the corporation’s employees contribute to a mini peak hour from 9 a.m. to 10 a.m. that is after the traditional morning peak.
  • The city no longer has to guess at seasonal variations in traffic because they keep the collected data in a database. Bellevue reports one of the city's more recent uses for the collected data was to track diversion from SR-520, which was recently converted to a toll facility.