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Adaptive Signal Control Technology: Managing Risks, Achieving Objectives
Eric Graves, P.E.Eric Graves, P.E.City Traffic EngineerAlpharetta, Georgia
Alpharetta Transportation System
• 50,00 Residents• Day Time Population~100,000– ADP– HP– UPS– North Point LCI– Downtown LCI
Alpharetta Transportation System• 4 Interchanges with GA 400 (Limited Access Freeway)• 7, 4-6 Lane Arterial Streets• ~ 120 Traffic Signals– 3 Emergency Signals at Fire Stations– 1 Hawk Signal – April
• All newer equipment – GDOT ATC Program– 332 cabinets– 2070 controllers – SEPAC Firmware– Ethernet Communications
• 60% direct connections to City TCC
Traffic Operations
• 2 Public Works Crews– Signs– Signals
• 1 Signal Systems Engineer• 1 Traffic Engineering Technician– Inspect Construction Projects– Manage maintenance contracts• Striping• Loop Repairs
Traffic Operations
• Signal Systems Engineer– Signal Timing Maintenance Program– Systemic timing of all traffic signals every 2-3
years– Before/After travel time measurements – Timing reports to be published on the City Web
Site (soon)
Why Adaptive??
• Less $$ available for capacity improvements• Less opportunity for new roadway connections – Alpharetta is land locked and nearly built out
• Essential we operate our system as efficiently as possible– Initiative included
• Systems / Timing Engineer• PM Program• Timing Maintenance Program
Why Adaptive ??
• Traffic STILL a top concern from citizen survey• What else can be done???
• Cobb County SCATS System– Councilman read article on SCATS Success• Directed Staff to investigate options for Alpharetta
When Adaptive Makes Sense
• Unpredictable Traffic Flow– High sustained growth– Freeway system interactions
When Adaptive Makes Sense
• Agency Capabilities– Technician capabilities• Detection at 98%!!• Strong communications
– Fiber along all major corridors– Stable Ethernet field network
When Adaptive Makes Sense
• Agency Capabilities– Engineering Staff• In-house signal timing maintenance program• “One of the best signal timers in the state”
When Adaptive Makes Sense
• Desire Continuously Optimized Timings!!
Alpharetta Adaptive Signal Evaluation: Hypothesis
A well-timed system is a well-timed system
Cycle length- appropriate for volume Split percentages- balanced or prioritized Offsets- provide good progression
Alpharetta’s Criteria• Should be able to perform close to manual
optimized timings• Maximize the utilization of existing infrastructure– 332 cabinets/ 2070 controllers/ SEPAC Firmware– Ethernet Communications/ECOMM
• Optimize Progression on Corridors• Provide Queue Management• Coordinate crossing arterials??• Manual control??– Special events/Seasonal Peaks/Incidents
Identified Solutions
• SCATS – Cobb County• SCOOT **OFFERED DEMO**• ACS Lite• InSync **OFFERED DEMO**
Identified Solutions
• The City of Alpharetta performed demonstration projects with two adaptive platforms– InSync and SCOOT
• The results of the demo projects indicated that adaptive solutions could replicate current timing efforts– Potentially improving operations for special
events, unexpected events, and off peaks periods
Other Systems Considered• SCATS – New Firmware– New Detection– Separate Central System
• OPAC– New Firmware– Separate Central System– Distributed solution – more rigorous detection
requirements• ACS Lite– Presently not available in TACTICS– Presently does not optimize cycle length
Next Steps• SR 9– Sandy Springs– Roswell– Alpharetta– GDOT
• 18 mile corridor– Collector between outer suburbs and GA 400
interchanges– Primary arterial (Sandy Springs/Roswell)– Back up for GA 400
• PM Team identified Adaptive as an ITS Strategy
SR 9 ATMS Project
• PM Team initially considered performance Spec– FHWA/GDOT indicated that as written only one
vender likely fulfilled requirements– FHWA determined documentation was insufficient
to sole source
SR 9 ATMS Project
• GDOT/FHWA Required PM Team to follow Federal Regulations mandating System Engineering Process to select Adaptive Solution
SR 9 ATMS Project
• Systems Engineering Report completed and accepted by FHWA – Systems Engineering Process identified similar
functional requirements as the Alpharetta demo projects
– SCOOT determined as preferred option• Compatible hardware with jurisdiction platform• Ability to coordinate with non-adaptive intersections
using Tactics Central System
SR 9 ATMS Project
• Project recently received NTP!!
