Sensors for safety in fog

SAFETY | Sensors for safety in fog

A smart detector beacon system uses sensors and LEDs to guide and warn drivers, improving safety for those travelling in dense foggy conditions

Words | Sandra Fernandes, marketing communications manager, Sernis, Portugal

If you can’t avoid fog entirely, the first thing you should do is increase the space between your vehicle and the vehicle in front of you. However, judging the distance can be quite a challenge since fog can significantly reduce your visibility.

There is often dense fog on the Autovía del Cantábrico (A-8) in Spain. The last section of the highway to be put into service – the Mondoñedo to Vilalba section – is in Alto Do Fiouco, 698m above sea level. Currents or air masses from the Cantabrian Sea in this area regularly create fog by orographic elevation.

On July 26, 2014, a serious multicar accident occurred on this section of highway, as a direct result of dense fog. The accident involved 40 vehicles and resulted in loss of life.

A smart solution

To try to improve safety on the highway, cameras and weather stations with visibilimeters that send information to the Northwest Traffic Management Centre every minute were installed. Since visibility conditions change very quickly here, the solution proved not to be very efficient. Dirección General de Tráfico (DGT) launched an open tender to develop a smart system that could alert drivers about fog immediately. In response Sernis developed Project BICA (Balizas Inteligentes Climatologia Adversa, in Spanish), a smart detector beacon system designed for adverse weather, particularly fog.

Each smart detector beacon has two powerful LED beacon windows, amber and red, with brightness control, for guidance. Each detector also has a set of a dedicated sensors (like radar sensors) and a local processing unit to detect vehicles and alert drivers in real time if they have traffic in front of them, even with very limited visibility conditions.

There are 382 units on this section of highway, covering a distance of around 4km of road. They are connected via an RS485 communication protocol, which makes it possible to communicate individually with each set of smart detector beacons, to monitor and control several internal parameters.

When there is reduced visibility or when meteorological elements prevent correct visibility, the smart system provides guidance and lane limitation through amber LEDs. It provides warnings and vehicle detection via red LEDs.

The system works according to three different scenarios: • Under normal conditions, all lighting devices remain off. • In low light conditions, either on a cloudy day or during the night, amber LEDs turn for guidance signalling. • In foggy conditions, vehicle detection and guidance lights are activated simultaneously. When the smart detector beacon system detects the passage of a vehicle, it activates red LEDs in the device for a predefined time to warn the following vehicle about the presence of another vehicle in front of it. The guidance lights (amber LEDs) remain active as guidance signaling.

Above left: Smart detector beacon system for dense fog warnings Above right: Project BICA in dense foggy conditions on the A-8 in Spain

Connected information

In addition to its main functionality, the smart detector beacon also monitors traffic flow between every set of two consecutive systems. This means that the software can continuously check vehicle correlation between the smart detector beacons and alert about possible accidents.

The 382 smart detector beacons are installed approximately every 48m on each side of the road on the A-8. Each point has become a detection barrier with doppler radar sensors. The management software was developed according to all DGT requirements, including integration in the existing road equipment management application in the Northwest Traffic Management Centre. After several tests that validated the results in the research, installation was completed at the end of 2021. To find out more, visit Sernis at Intertraffic Amsterdam 2022 (March 29 – April 1, 2022) on booth 01.207. ■