Let’s say you have the choice between two vehicles. The first is a brand new vehicle designed and built to your exact specifications, from the amount of leg room to the color to how many cup holders there are. The second is a combustion engine used for a lawn mower with seats and tires bolted on. Which one would you choose? Unless you’re hoping for a rickety go-cart, you’d probably choose the vehicle custom made for you. While a lawnmower engine is perfect for a lawnmower, you wouldn’t want to power a car with one.
In the ITS industry today, we’re seeing a trend that is a lot like using a lawn mower engine in a car- and the results are often just as disappointing.
First, a bit of history. While the concept of Intelligent Transportation Systems has been around for decades, it wasn’t until after the year 2000 when the industry began to see technologies that changed the way we looked at detection. Before that, inductive loops buried in the ground were the standard for vehicle detection. These inductive loops were state of the art... in the 1970s.
Inductive loops are very accurate, but have a wide array of problems associated with their intrusive nature. They are difficult, costly and often dangerous to install, they are easily broken and require expensive and extensive repair systems. They require road closures and only work with a pristine road surface as any issues could cause failures.
The industry saw the problems with loops and attempted to move vehicle detection out of the ground, but many early non-intrusive systems had their own problems. Transportation agencies were sold on the convinces of non-intrusive technology only to be burned by low accuracies and high failures. These failures were especially evident in camera-based detection where low-light, fog, sun-glare and dirty lenses rendered the promise of accurate detection worthless.
The problem many of these systems faced was they were using technologies made for non-transportation applications and trying to force that into the ITS world. The industry demanded better from detection manufacturers.
The solution to this problem occurred when manufacturers used custom engineering to create technologies built from the ground up for the traffic and ITS industry.
From this mindset, one vehicle detection technology emerged as a viable replacement for inductive loops. It’s radar and it’s the result of some of the best radar experts in the world coming together with some of the best traffic experts in the world and creating an entirely new system unlike every other radar application. By creating a highly reliable digital system specifically for the traffic and ITS industry, radar became the technological choice for ITS projects around the world.
How reliable is radar? Over 15 years worth of third party testing has shown high-resolution, ITS specific radar often outperforms loops, as well as other detection devices, when it comes to factors like reliability, life-cycle costs, ease of installation and, of course, accuracy.
In the real world, tens of thousands of installations across the globe with more than a billion detections daily prove radar technology is reliable, accurate and non-intrusive placing it front and center for vehicle detection. More and more it is evident that proven radar traffic sensors are not only the good choice when matched with the right application, they’re the right choice.
Of course, any technology on its own has little value without the community hundreds of traffic experts around the world who utilize ITS specific radar technology bringing with them countless years of experience and expertise.
Now we are seeing a new problem. Since radar has been proven, many manufacturers have jumped on the radar bandwagon, but rather than build a traffic and ITS specific radar system, they use off-the-shelf radar or even try to shoehorn radar created for other industries into the ITS sector. Just like utilizing a lawn mower engine for a car- this type of technological jerry-rigging showcases a fundamental misunderstanding of how radar works and how it can work for the ITS community.
How then do you determine which radar technologies are best for which application? Let’s look at a few applications and see what qualifications radar detection requires for each.
Probably the most basic requirement of any vehicle detection system is to gather data. Intelligent systems require a large variety of data including counts, per vehicle speed, vehicle classification, lane occupancy, 85th percentile speed, gap, headway, direction of travel and more. Additionally, this data needs to be gathered on freeways and roadways with an increasing number of lanes. Radar detection should be able to gather all of this data on both sides of the freeway on all lanes, sometimes this means providing data for over 20 lanes.
Many repurposed radar sensors use a single radar beam with a wide width, side to side, and a narrow field of view, top to bottom. A wide width is usually fine for around six lanes but after that it is unable to detect more than one vehicle in the beam at a time leading to diminished accuracies for all data. At the same time, a narrow field of view will limit the number of lanes a sensor can see.
Traffic radar built for the ITS industry should have a narrow beam width, as small as seven degrees, and a wide field of view, usually 65 degrees to provide both flexibility and accuracy for up to 22 lanes.
Data accuracies also go up when traffic radar detection becomes vehicle based rather than lane based. In order to do this, radar must operate on a higher frequency, 245 MHz and then use the full spectrum of that frequency.
For example, if a radar uses only 50 to 100 MHz of the 245 MHz bandwidth, it cannot resolve closely spaced objects and can only provide lane-based detection. Meanwhile, a traffic radar sensor that uses the full spectrum of the 245 MHz bandwidth is able to provide vehicle based detection using a two-foot resolution which finely detects objects closely spaced together. Think of it as the difference between standard definition and high definition. High definition detection leads to drastic increases in accuracies. especially with lane-changing vehicles or when lanes are skewed do to weather or construction.
This ITS application has become both common and useful in controlling congestion in a number of scenarios. It requires mainline detection either by approach or by lane and requires accurate per-vehicle speeds. Best practices for this application says that 85th percentile speed should be used. Traditionally, a speed trap is created using two inductive loops per lane to calculate true per vehicle speed.
Repurposed radar sensors either utilize a radar capable of creating a Doppler affect or use a single radar beam that can only provide speed based on duration and assumed length. Neither of these technologies provide per vehicle speeds relying instead on average speeds. All speed data created, therefore, is an estimate.
Some non-traffic radar technologies use multiple beams but are not side fired. In these cases, radar beams are used only to differentiate lanes, not create speed traps. This technology, called monopulse radar, has some serious limitations. First, it is limited in the number of lanes which can be detected. It also has problems differentiating vehicles at the same distance from the radar- a hindrance that causes inaccurate counts.
Radar technology created for the ITS industry utilizes a dual-beam, side fire radar array which creates a speed trap that measures true per-vehicle speed for every lane. This, along with accurate lane occupancy counts means the pinpoint accuracy needed to accurately create variable speed limits, sometimes on a lane-by-lane basis, is met.
This is an ITS application that is saving lives. It requires accurate vehicle based detection capable of detecting direction of travel.
Repurposed radar sensors use a single radar beam and cannot provide any reference point to which direction the vehicle is traveling.
Radar technology created for the ITS industry utilizes a high-resolution dual beam array creating two points of reference for what is known as a/b logic. If a vehicle is traveling from a to b, everything is fine. If a vehicle is traveling from b to a, it identifies it as a wrong-way vehicle and can, in real time, activate warning signs and contact law enforcement.
The ability to proactively activate HOT lane designations requires highly accurate multiple lane vehicle and occupancy counts.
Here, repurposed radar sensors, including single beam and monopulse systems, face the same issues we discussed before: Their ability to provide accurate occupancy and specific lane data is quite limited.
Again, radar technology created for the ITS industry requires a narrow beam and a wide field of view to give accurate lane specific data across the entire roadway. A dual beam array is also required for speed data.
The pattern here is clear. Repurposed radar doesn’t provide the accuracy or detection ability needed for ITS applications because it wasn’t created for these systems. All of these applications as well as others such as trip times, incident management, congestion alerts, speed maps, ramp metering, work zone management and others require radar sensors built for the traffic industry. They must be able to detect more than 20 lanes of traffic with one unit; use a dual beam array; use the full bandwidth of the 24 Mhz and be proven both in third party studies and in real-world applications.
The good news in all of this is that by utilizing radar traffic sensors created for the ITS industry traffic engineers around the world are creating new and innovative applications. By refocusing the time, cost and effort of installing and maintaining loops while having an entire suite of proven accurate data at their fingertips, many of the hindrances to effective systems have been removed and the sky is the limit.
We know working in the transportation sector can be a thankless job, but it’s one of the most important. Safe and efficient roadways affect everyone whether they realize it or not. Radar is a proven tool to help make roads safer and more efficient, but only when that radar is built for the ITS industry. Using the right tool for the job is key to your success in providing safe and efficient roadways.