Signal operations have evolved into sophisticated networks. For example, adaptive control systems monitor traffic conditions and adjust signal phases accordingly, reacting to current data rather than average time-of-day settings that traditional methods use.
Replacing older systems that use pre-programmed, daily signal-timing schedules with a more advanced adaptive control system accommodates changing traffic patterns and eases congestion. With the use of adaptive systems, signal timing is more flexible and efficient.
Although adaptive systems may not be a silver bullet, they can be very beneficial when used at intersections that face flexible and inconsistent traffic patterns that traffic plans can’t keep up with. In areas that have unpredictable traffic, adaptive systems might be useful because plans are updated in real time.
“Adaptive is most suitable for tackling traffic problems at intersections that see a lot of variation in traffic patterns,” says Brad Giles, a research engineer at Wavetronix. “In places that traffic patterns aren’t as established from one day to the next there is a need for something more flexible.”
Although adaptive systems may not be a silver bullet, they can be very beneficial when used at intersections that face flexible and inconsistent traffic patterns that traffic plans can’t keep up with.
The need for accurate data has never been more important because detection is relied upon to do more in adaptive traffic control. Accurate detection is key to the success of any adaptive system because it implements local control policy in real time. Therefore, the selection of sensor equipment for adaptive systems is extremely critical for at least three reasons:
First, the implementation of local control policy in adaptive systems is usually like that of traditional actuated systems. Local stop bar and advance detectors are used to manage how much of each cycle’s planned split values are invoked in real time.
Second, over time local control policy adapts. This is different than actuated systems, because now the planned split values themselves are updated to match predictable changes in volume of vehicles moving from each leg of the intersection onto all other legs of the intersection.
Third, the detection adapts system control policy over time. This too is different from actuated systems. Now system-level settings such as the common cycle length shared between intersections and the relative start-of-green offsets used between intersections are updated to match predictable changes in the overall volume of traffic and intersection-to-intersection travel times.
“The advantage with adaptive is that if the detection is reliable, then local control and system control will stay more relevant over time,” Giles says. “However, if the detection is biased or imprecise this added value will not be realized. At the same time, one risk with having something that is more flexible is that it can be prone to adapt incorrectly. In fact, without reliable detection the intersection’s operational performance will be negatively impacted in real time and over time.”
An adaptive system will suffer if the data from the chosen detection is unreliable, incomplete, or inaccurate. The fact is that the adaptive system will fall back into the performance level of a fixed timing system if detection has a 15 percent or greater failure rate and faults are not rectified.
Wavetronix provides radar detection that delivers the accurate data required for a well running adaptive system. No matter the system there is a SmartSensor that will fit, with detection that is flexible enough to work in many different adaptive systems, from the very first to the very newest and anywhere in-between.
Often adaptive systems are sold as a packaged solution with specific detection. But in reality, they are compatible with Wavetronix radar detection. For example, SCATS (Sydney Coordinated Adaptive Traffic System) was originally designed for fifteen-foot loops, but SmartSensor Matrix has been used successfully with SCATS because the sensor can integrate like a loop with the advantage of being non-intrusive. In fact, Wavetronix radar detection has been integrated into a number of adaptive systems, including ACS-Lite, InSync, SCATS, SCOOT, Surtrac, Kadence, Centracs Adaptive and SynchroGreen, to name a few.
Brett Sellers, P.E. has experience with Wavetronix’ integration into SCATS, which counts vehicles utilizing stop bar detection. The system he managed was installed initially using video detection from a side-fire angle which caused several problems.
“We installed SmartSensor Matrix and the Click 650 at a couple of our headache intersections and gained immediate improvement. Mapping the detection into the system was easy and networking the Click 650 was a breeze, allowing remote connectivity to modify or troubleshoot from the office,” says Sellers, who now works as a technical sales representative in Wavetronix’ Tennessee/Alabama office. “Not only did we eliminate false and missed calls on mainline left turn movements and side street approaches, but we improved detection accuracy on the mainline.”
“We installed SmartSensor Matrix and the Click 650 at a couple of our headache intersections and gained immediate improvement. Mapping the detection into the system was easy and networking the Click 650 was a breeze, allowing remote connectivity to modify or troubleshoot from the office,” —BRETT SELLERS, P.E.
The improved accuracy on the mainline counts allowed the system to make better decisions concerning cycle lengths, therefore improving the efficiency of the most congested segment of the corridor.
Today, there are many adaptive systems on the market, all of which incorporate traffic data into their own algorithms that require various detection layouts. The detection layout is based on whether the approach to an intersection is an entry/exit link to the system or an approach internal to the system.
Usually used to adapt local control policy (specifically the “split” of green time allocated to different movements of conflicting traffic flow). Most adaptive systems rely upon lane-by-lane stop bar detection to help measure “who” should get “how much” green time. Volume and occupancy measurements from each lane are mapped to specific turn/through movements in order to best distribute the green time.
Usually used to adapt system control policy (specifically the offset of the start-of-mainline-green from one intersection to the next). Advance detection is detection beyond the queue. Beyond queue detection is important because it allows the time-of-arrival of the majority of vehicles to be recorded. Stop bar detection would only record the time-of-arrival of the first vehicle and is much less useful for system control.
Usually used to predict the arrival of vehicles at a downstream intersection rather than directly detect their arrival beyond the queue.
“Generally speaking, adaptive systems are designed to only use detection in some of these locations,” says Giles. “For example, SCATS uses stop bar detection but does not use exit detection or advance detection anywhere.”
Wavetronix has flexible radar detection that will work at any expected mainline and entry link placement required by individual adaptive systems. SmartSensor Matrix is used for detection required at the stop bar or for exit detection, and offers lane-by-lane detection and the flexibility to create detection zones at both the stop bar and the exiting side of the intersection. A single Matrix can be used for stop bar and exit detection for each leg of the intersection. For example, an arterial with three lanes in each direction can use one Matrix for stop bar and exit detection instead of six loops.
For detection required in advance of the stop bar, a SmartSensor HD or SmartSensor Advance can be used. SmartSensor HD is used when integration into the central system to collect interval data is wanted or if lane-by-lane advance detection is needed. SmartSensor Advance can also provide dilemma zone protection, help collect arrival profile information, and be used for signal performance measure systems.
“SmartSensor Advance’s detection is different from lane-by-lane advance loop detection, but by using radar tracking, it produces statistically-equivalent arrival profiles from the perspective of adaptive offset optimization algorithms,” Giles says. “This makes it a cost-effective retrofit for adaptive systems that specify lane-by-lane loops without the hassle of trenching long distances and with the benefits of dynamic dilemma zone protection. Road managers that want to try this out can collect arrival profiles with the new Click 650 for retrofit validation.”
An adaptive control system can ease congestion by changing signal timing plans in real time based on traffic conditions. When an adaptive system is determined to be a good solution for a problem area the selection of appropriate detection is of great importance. Reliable detection will maintain that the system will be as efficient as possible. Wavetronix provides the necessary detection required for various detection layouts and can be incorporated into almost any adaptive system on the market.
The 650's small profile packs a big punch and will help get your adaptive system humming in no time.
