ITS and solid-state lidars

Improving ITS with solid-state lidars

Lidar sensing technology continues to evolve, as new suppliers redefine optical detection and ranging capabilities with groundbreaking innovations. New solid-state lidar technology is set to change the face of ITS

Words | Stéphane Duquet, LeddarTech, Canada

Solid-state lidars deliver precise multi-target detection and measurement in applications such as e-tolling, vehicle counting and profiling and speed measurement

Lidar technologies have been deployed in specialized intelligent transportation systems (ITS) applications for a some time. Their benefits – including distance measurement precision, resolution, and resilience to changing lighting conditions – have justified their use in applications such as highway tolling, despite coming with a hefty price tag.

Laser scanners have limitations. Their mechanical components and complex builds can affect their reliability over time and can make them expensive to deploy, especially if the intended application requires sensors. Their collimated light beams also make them more sensitive to rain, snow, or fog.

Today, a new generation of lidars is available for ITS applications from vendors that use solid-state designs and flash illumination to produce highly efficient, robust lidar with no moving parts. These lidars also drive sensor prices down from thousands to hundreds of dollars, making them appealing for broader deployments.

As one of the pioneering solid-state lidar (SSL) manufacturers, LeddarTech first introduced the technology to the ITS market 10 years ago and since then, the company has continued to improve its SSL product performances, filing more than 55 patents. Its first commercial application was in advanced traffic management systems (ATMS), using lidar as a stop bar for traffic detection. Placed above ground on existing infrastructures, SSL indeed represented an attractive alternative to induction loops for traffic light automation.

While some forward-looking cities have been quick to adopt SSL sensing to manage critical intersections, the ITS industry as a whole has taken some time to embrace it. But this mindset is changing, as integrators and operators realize the potential to improve mobility through the implementation of cost-effective lidars in smart city, intelligent highway, and dynamic traffic monitoring applications.

SSL advantages

SSLs are compact, robust, affordable, and easy to integrate into existing hardware and roadside structures, providing reliable detection and ranging data.

Compared to laser scanners, SSLs typically use diffuse light sources, which generate weaker return signals (the quantity of light reflected back from the object) and reduce the sensors’ performance and range. Through proprietary algorithms and advanced signal processing, LeddarTech can deliver performances that rival those of their scanning counterparts, with the use of low-cost, solid-state optical designs and components.

SSLs can be deployed in ITS as standalone units or in combination with

other sensors, such as cameras, radars, or induction loops, to provide complementary information and redundancy. Compared to radars, lidars offer distinct benefits, including higher resolution, more consistent detection of various types of objects (for example, pedestrians, still objects, etc.), better multi-object discrimination, and easier beam forming. Lidars also provide significant benefits over camera-based solutions, with robust detection in any lighting conditions, longer effective range, more accurate distance measurements, and better performance in inclement weather.

Intensive benchmarking of these different technologies is currently being performed in the automotive industry, where detection performance and reliability is paramount to ensuring the safety of vehicle occupants, particularly with the advent of autonomous driving functions. This industry has reached a quasi-unanimous consensus that lidars bring unique capabilities – and that they will be a key element in establishing the 360° ‘detection cocoon’ required around the vehicle.

Therefore, while radar and camera-based solutions are currently being deployed for basic driver assistance functions, upcoming generations of cars should increasingly rely on new combinations of cameras and lidars for both short- and long-range detection. The same cost and performance benefits seen in automotive applications apply to ITS, which faces similar challenges in the reliable detection of various types of traffic.

Using SSL in ITS applications

SSLs are versatile sensors that capture a variety of traffic information, such as the location of vehicles, cyclists, or pedestrians; dimension measurements; and direction and speed data. This makes SSLs very attractive for use in various ITS applications.

As previously mentioned, SSL-based traffic management systems provide accurate stop-bar detection functionalities over multiple traffic lanes, for traffic light automation at busy intersections. Above-ground installation makes SSLs easy to deploy and maintain. They can be combined with cameras and automatic license plate recognition (ALPR) systems for enhanced functionalities, including traffic violation enforcement. Consequently, SSL is increasingly viewed as a versatile alternative to underground induction loop sensors.

SSLs can also be used in automated tolling (e-tolls). Their highly accurate and consistent distance measurements make them ideal vehicle detectors for triggering ALPR systems.

SSLs’ precise beam-forming and customizable detection areas also make them particularly suitable for detection systems at pedestrian and bicycle crossings. They have the potential to replace traditional pelican crossings and to enable advanced traffic light automation.

Speed enforcement and mitigation systems also use SSLs’ multi-object ranging capabilities to simultaneously measure the speed of several vehicles within a wide detection area. For such applications, the sensor benefits from having higher refresh rates, thereby ensuring maximum performance and responsiveness, even at very high speeds.

SSLs can be used to estimate the dimensions and shapes of fast-moving vehicles, thanks to their ability to measure multiple segments with high sampling rates within their field-of-view. Vehicles can then be classified by size and type against application-defined criteria. Such capabilities can be leveraged in applications including e-tolling, gated access control, public transit vehicle priority systems, and clearance warning for overpasses, tunnels and other structures. Smart cities looking to monitor high-traffic areas in real time will also be able to deploy a comprehensive network of SSL sensors to collect valuable data and optimize the use of their existing infrastructure.

A bright future for optical sensing

As SSL technology continues to evolve, lidar is set for a bright future in ITS. Sensors will become an integral part of smart mobility and a key enabler in increasing transportation efficiency. It is foreseeable that all major roads will eventually be systematically monitored by an array of low-cost sensors, such as SSLs, with key traffic information being exchanged dynamically between passing vehicles that provide insights and relay information through vehicle-to-infrastructure (V2I) communications networks. This future may be much closer that we can envision, made possible by breakthrough innovations such as solid-state lidars enabling the high-volume deployment of versatile, cost-efficient optical sensors in ITS. n

Left: Beyond vehicle traffic,

Leddar sensors excel at pedestrian and cyclist detection. This makes them a sensor of choice for automating crosswalk and bike lane signals at busy intersections