“Unlike their predecessors, these adaptive systems are not based on a fixed cycle length; they can adjust the split, offset, cycle lengths, and phase order of the control signal,” FHWA says. “ACS uses sensors to interpret characteristics of traffic approaching a traffic signal and, using mathematical and predictive algorithms, adapts the signal timings accordingly, optimizing their performance.”
Adaptive signal control is so appealing that on May 22, at the American Association of State Highway and Transportation Officials (AASHTO) spring meeting in Natchez, Miss., Federal Highway Administrator Victor Mendez announced that adaptive signal control technology would be one of several innovative technologies selected for accelerated deployment under his 2010 Every Day Counts initiative.
Other technologies selected were warm mix asphalt, geosynthetic reinforced soil integrated bridge systems, and prefabricated bridge elements and systems.
FHWA will host a series of strategic regional summits this fall to promote the deployment efforts, and to more broadly engage stakeholders who will be involved in mainstreaming the technologies.
New York City is developing a new integrated adaptive signal control decision support system, and is implementing it on two New York City arterials. In their 2010 Transportation Research Board paper Integrated Adaptive Traffic Signal Control with Real-Time Decision Support, authors Xin, Chang, Bertoli and Talas describe a new integrated adaptive signal control decision support system for use in the Big Apple.
Featuring mixed control objectives for both under- and over-saturated traffic, the system integrates a just-in-time “microscopic” traffic simulation framework, enabling the operator to supervise, review, and interact with signal operations in real time by verifying algorithm-optimized strategies against other alternatives.
In addition to the “operator-in-the-loop” mode, the new system also supports autonomous signal optimization without operator interactions. Current implementation covers two arterials in New York City, i.e., Victory Boulevard in Staten Island with four intersections, and a section of Route 9A in Manhattan with 22 intersections.
But ACS is not limited to big governments. In November 2007, the City of Tyler, Tex., deployed the ACS-Lite technology along a 3.17-mile corridor. The deployment included $150,600 for the software module, $38,400 for traffic communication system upgrades, and $357,900 for detection devices.
Citing the results of a study of the ACS installation, the Tyler newspaper reported that on peak traffic hours on weekday mornings, motorists experienced the largest drop in drive times, with the average trip time in both directions dropping from just more than nine minutes each way to less than six minutes. On average, motorists’ amount of stops dropped from 2.9 on the route to one stop per trip while traveling north, and from 3.1 to two per trip travelling south.
Middays, the average northbound trip time dropped from about 9.5 minutes to 8 minutes and 46 seconds, and the southbound trip was taking seven minutes, which was only nine seconds less than what it was before.
And at weekday peak evening hours, the northbound trip time was down by about 40 seconds to just less than nine minutes and the southbound trip time down by about a minute to less than eight minutes a trip.
Improving Dynamic Message Signs
Another relatively low-cost way ITS is impacting today’s drivers is via dynamic message signs (DMS), which are an important component of advanced traveler information systems. Such ATIS provide a powerful venue by which real time traffic information is accessed by motorists.
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