Adaptive Signal Control in Atlanta District

Rebecca Wells, P.E. TxDOT Atlanta

Why Adaptive Control

• Typical corridor has timing plan – Time of Day – Days of week changes – School, annual special

events, etc. Works okay, Signal technicians are

reactive to problems

Striving for Excellence

• Reduce travel time • Increase efficiency of corridor • Reduce delay • Proactive operations

Traditional Upkeep

• Periodically retime corridors • Difficult for District Staff to

have resources to do with our personnel

• $1500 to $3500 per intersection to retime – Temporary benefit – Lack of funding for consultant

work

Various adaptive control systems

• Real time adaptive control – Reacts to the traffic as it happens, adjusts timing

to best serve, real time traffic

• Responsive adaptive control – Evaluates what is happening at the intersection

over several cycles, and adjusts timing over a period of time

Various systems

• Several minor players, but don’t have many deployments

• SCOOT • SCATS • InSync • ACSLite

SCOOT

• Avg installation cost per intersection $30,000 to $60,000

• About 25 hours per intersection to install

• Avg 13 hours per week per intersection maintenance time

• Approx 13% time downtime

SCOOT

• Proprietary controller • Specific detectors required • Handles up to 255

intersections • Can work with grid system

SCATS

• Avg installation cost per intersection $30,000 to $60,000

• About 13 hours per intersection to install

• Avg 8 hours per week per intersection maintenance time

• Approx 4% down time

SCATS benefits

• Limited types of controller can be used

• Specific detector required • Handle 250 intersections • Linear Arterial only

InSync

• Avg installation cost per intersection $25,000 to $35,000

• About 19 hours per intersection to install

• Avg 5 hours per week per intersection maintenance time

• Approx 2% down time

InSync

• Proprietary controllers required • Specific cameras required • Linear arterial only

InSync

• HDR 2010 survey -most felt system met or exceeded their expectations for reducing overall delay, decreasing number of stops, or improving the overall travel time

• Issues with communications and detection

• At times, registers false positives and misses calls

InSync • Video detection and

communications a concern for most survey respondents

• Greatest improvement during peak period travel times

• Only Real Time Adaptive Traffic Control

ACS Lite

• Avg installation cost per intersection $12,000 to $38,000

• About 7 hours per intersection to install

• Avg 6 hours per week per intersection maintenance time

• Approx 9% downtime

ACS Lite

• Variety of controllers (NTCIP) • Flexible on type of detectors • 16 intersection or 32

intersections depending upon communication availability

• Linear arterial only

ACS Lite

• HDR 2010 - Most felt the system met or exceeded their expectations of decreasing arterial delay, decreasing number of stops, reducing intersection delay

• Does not work in a grid patter • Does not work well with short duration high

volume peak

ACS Lite

• Overall ACS lite is the least labor intensive for installation and fine tuning

• Issues with communications most common problem

• Designed to be low-risk approach to ASCT

• Developed with public/private partnership (FHWA)

ACS Lite • What does it do?

– Balance Utilization of Green – Adjusts Splits – balances demands across all phases – Adjusts Offsets – monitors changing speeds of

platoons and system throughput

City of Marshall

• US 59 AADT 27,000 – US 80 AADT 15,900 – Major US Route

• Tourism • Industry • Recreation

City of Marshall

Typical System Architecture varies depending upon communications and setup

Detector Placement – any type of detectors Stop bar detectors for all approaches - Cameras Need advance detectors for platoons on main arterial – Wavetronix RADD

Optimize the phase utilization

ACS Lite

• Keeps controller’s timing as standard

• Downloads new splits and offsets for the currently running pattern every five to fifteen minutes, maintaining the same cycle length for that time of day.

Does it work?

• Measure of Effectiveness and Performance Evaluation – Smooth flow on arterial, two-way

progression – Manage queues – Manage side street flows – Prevent or delay oversaturation – Reduce variance

• Flow Profile – Displays date per detector for each approach – Percent greens (green), occupancy (blue), and capture

(black) – Works to maximum capture

Pattern History

Split Adjustments

Marshall, Tx • CSJ 0062-06-051 • Special Spec 8778-2001 • Bid Item $90,000 • Contract Start Jan 2012 • 240 Working Days • Project ends early Dec

Marshall, Tx

• Has redlight running equipment

• Installed RADDs poles to see platoons

• Cellular modem

Marshall, Tx

• One Master at US 59 @ US 80 • 3 additional intersections connected • 6 more intersection to include

Marshall, Tx

• Upgrade controllers • Install detection

devices • Install modems

Adaptive Signal Control

• Adaptive Traffic Control Signals will not replace the need for signal technicians, but should help fine tune an operable system