Texas Department of Transportation
When the freeways around Houston experience heavy congestion, motorists naturally divert to less-crowded frontage roads. To keep traffic moving on both routes, the Texas Department of Transportation has deployed a freeway adaptive system that uses the Wavetronix SmartSensor HD for vehicle detection. This system can adapt the signal timing patterns at frontage road intersections in order to maximize traffic flow.
The signalized intersections on Houston’s frontage roads were often controlled by time-of-day programs, which were designed to accommodate higher traffic volumes during peak traffic times. However, time-of-day systems change at scheduled times whether it is warranted or not, and they cannot respond to changes in traffic volumes that occur as a result of unplanned or special events, such as holidays and vacations; hurricane evacuation plans; and accidents on the freeway that cause traffic to be diverted onto frontage roads. According to Steve Chiu, the TxDOT engineering specialist in charge of the project, multiple attempts have been made in the past to manipulate intersection timing based on freeway conditions with limited success.
TxDOT implemented a system that uses SmartSensor HD to monitor freeway traffic. When heavy traffic on the freeway is detected, the system triggers an output to intersections on the frontage road, changing the signal timing patterns to accommodate more traffic, either by coordinating intersections for progression or by simply providing more green time in a free-mode operation.
HD’s patented dual-beam radar design detects volume, lane occupancy and individual vehicle speeds for up to 22 lanes of traffic. When a user-defined presence threshold is met, HD triggers a Click 513 contact closure, which generates an output that is delivered to traffic controllers via a 900 MHz radio. This output triggers the controller to initiate a preprogrammed timing pattern, which allows traffic to flow more freely through frontage road intersections.
This system was tested in a pilot project on Highway 290 west of Houston that used one HD sensor to control three intersections. A second installation on Highway 10 west of Houston uses three sensors to control six intersections.
“Wavetronix was chosen for this project because it has the most capable and complete selection of equipment that meets the need of the freeway adaptive system, and it is the most reliable and user-friendly sensor.”–STEVE CHIU, TXDOT ENGINEERING SPECIALIST
Chiu says the two current deployments are providing more green time to frontage roads when the freeway is overstressed, leading to less traffic, less wasted fuel and a more responsive traffic system. Says Chiu: “Wavetronix was chosen for this project because it has the most capable and complete selection of equipment that meets the need of the freeway adaptive system, and it is the most reliable and user-friendly sensor.”
