Intelligent control of street lighting systems is becoming increasingly important. Choosing the right sensor technology plays a crucial role. While traditional motion detectors such as PIR sensors or camera systems have their strengths, radar technology offers a number of advantages that make it the ideal solution for many applications. What technologies are available and what are their advantages and disadvantages?

- PIR (Passive Infrared) sensors: These low-cost, heat-sensitive sensors are sensitive to environmental conditions and have a limited range. A temperature difference of 2 to 4°C is required between the target and the environment to ensure a reliable measurement.
How they work: PIR sensors detect changes in the infrared radiation emitted by warm objects. When a warm object (such as a person) moves through the sensor’s field of view, the infrared radiation striking the element changes. The sensor interprets this change as movement.
Limitations: The detection of thermal radiation is limited to a certain distance, which limits the detection range of PIR sensors. Typically, PIR sensors have a coverage angle of 120° and a range of up to 10 metres. In addition, factors such as draughts, direct sunlight or extreme temperatures can cause objects to go undetected.
- Radar sensors: Radar sensors offer high reliability and long range, regardless of light conditions and temperature. They provide vehicle and pedestrian detection and precise motion detection.
Functionality: By emitting microwaves and analysing the reflected signals, radar sensors can detect movement. When the emitted microwaves hit an object, they are reflected and picked up by the radar’s receiver module. Changes in the frequency or amplitude of the reflected waves indicate movement. Complex algorithms analyse this data and enable precise motion detection.
Limitations: Although radar sensors have many advantages, they also have limitations. For example, weather conditions such as high winds, rain or snowfall can cause false alarms by misinterpreting them as movement.
- Camera systems: Camera systems work well for access control and number plate recognition. However, they are often too complex and costly for lighting control alone. There are also conflicts with GDPR, the General Data Protection Regulation.
- Ultrasonic sensors: These sensors measure distance accurately, but are limited to a very short range. They are also affected by temperature, humidity and obstructions.
- Induction loops: These loops, buried in the ground, detect vehicles but are limited to metallic objects and require a high level of installation and maintenance.

The advantages of radar at a glance
A major advantage of radar sensors is their range: they can reliably detect movement over long distances. For example, the lixtec lix.one radar sensor can detect cars up to 70 metres away and trucks up to 100 metres away.
Radar sensors also have a wide detection angle. The lixtec lix.pure radar sensor, for example, is ideal for car parks, pedestrian crossings and footpaths because it perfectly detects an elliptical area directly under the luminaire without any blind spots. PIR sensors, on the other hand, typically have a smaller detection angle and are more sensitive to orientation. They are designed to best detect movement perpendicular to their detection area. Objects moving directly towards the sensor, or at a very flat angle, may be harder to detect. This is because PIR sensors react to changes in thermal radiation caused by movement across their detection zones.
The high accuracy of radar sensors, on the other hand, makes it possible not only to determine the exact distance to an object, but also to measure its speed. This versatility makes radar sensors interesting for a wide range of applications, from simple motion detection to complex control of traffic systems, where lixtec sensors provide the necessary data to increase the light to a pre-defined level only when a road user approaches, and then reduce it back to (for example) 10% of the brightness after the user has passed, opening up enormous potential for energy, CO2 and cost savings.

The future of cities: radar as a building block for smart city solutions
The use of radar sensors in street lighting is just the beginning. Widespread installation of such sensors on street lights will create a dense network of data points that will open up entirely new possibilities for urban planning and control.
Just imagine: Every streetlight becomes an intelligent hub that continuously collects data on traffic flow. This data can be analysed in real time to create a comprehensive picture of the traffic situation. For example, the volume of traffic can be accurately recorded and analysed by vehicle type and speed.
The knowledge gained can be used for a variety of applications:
- Intelligent traffic management: Traffic jams can be avoided and traffic flow optimised by adapting traffic lights to the current volume of traffic.
- Public transport optimisation: Public transport timetables can be adapted to actual traffic conditions to ensure greater punctuality and efficiency.
- Planning new infrastructure: Traffic data can be used to plan new roads, cycle paths and public transport.
- Identify traffic problems: The data can be used to identify potential hazards and take action to improve road safety.
- Develop new services: The data can be used to develop new mobility-related services, such as car-sharing services or navigation systems that provide real-time traffic information.
Integrating radar sensors into a comprehensive IoT system makes it possible to make cities smarter and more efficient. The networking of different sensors and devices can open up completely new applications. The possibilities are almost limitless. One thing is certain: radar technology will play a crucial role in the development of smart cities.
Literature and sources:
2013: „Principles of Modern Radar“, William L. Melvin und James A. Scheer
2024: https://semiengineering.com/radar-vs-pir-selecting-the-right-solution/
2024: http://de.solar-led-lights.com/info/what-s-the-difference-between-radar-sensor-and-95476458.html
2021: https://radar-blog.innosent.de/duell-der-bewegungsdetektion-pir-versus-radar/