By Jonathan Chadwick

Poland is pioneering new road signs that combine an array of sensors to monitor road traffic and conditions to warn drivers of hazards on the road ahead.  
  • Polish project is creating smart road signs for adaptive control of vehicle traffic
  • The signs combine video cameras, weather sensors and acoustic vector sensors
  • And they feature built-in Doppler radar – a technique based on the Doppler effect

Researchers are building ‘intelligent’ motorway signs to track traffic volume and alert drivers in real time to potential dangers as part of a national project called INZNAK. 

AVS reads reflected sound waves and calculates traffic on a particular stretch of motorway, which can then be relayed to drivers to warn of congestion.

Researchers in Poland have created smart road signs (pictured) that use built-in Doppler radar, video, and acoustic radar and weather stations to monitor road traffic and conditions to warn drivers in real-time of hazards and prevent collisions on highways 
Polish researchers say the technology would allow road signs to constantly detect traffic on the road and use this, and a host of other data, to warn drivers of any potential hazards ahead 


The Doppler effect, or Doppler shift, describes the changes in frequency of any kind of sound or light wave produced by a moving source with respect to an observer 

The Doppler Effect is a well-understood physical phenomenon which is also seen in astrophysics as the universe expands and creates ‘redshifting’, but is more commonly seen in sirens. 

For example, when a blaring ambulance or police car shoots past with its sirens on, they seem high pitched as they approach you and then lower pitched as they speed past. 

This is due to the compression of sound waves as they come closer, and they then stretch out as they grow more distant. 

A stretched out sound wave has a greater wavelength, and therefore a lower frequency, resulting in an increasingly lower pitch.    

The smart road signs also come equipped with built-in Doppler radar – a specialised radar technique based on the Doppler effect. 

Doppler radar is already used along roads to read how fast cars are travelling and tell the drivers to slow down if they’re travelling above the speed limit, as well as in police speed guns.  

In smart road signs, Doppler radar measures the velocity of objects such as cars or drops of precipitation hitting the roads. 

When rolled out, a whole network of signs would also communicate via vehicle-to-everything (V2X) technology – a form of Wi-Fi designed for fast-moving objects that lets Bluetooth-enabled smartphones and cars talk to each other. 

The whole project is being financed by the Polish National Centre for Research and Development, the country’s public agency for scientific innovation. 

Lead project scientist Andrzej Czyzewski, from Gdansk University of Technology in Poland, is describing his work at the 179th Meeting of the Acoustical Society of America, which is being held virtually from December 7-10.

‘We can calibrate an acoustic vector sensor [AVS] so it can be used to measure highway traffic volume and count vehicles by analysing the noise they emit as they go by,’ said Czyzewski. 

‘When it is successfully implemented, the devices developed by us will communicate with each other in V2X technology and actively react to the traffic situation, suggesting to drivers the speed appropriate to the situation.’

This technology was poised to be rolled out earlier this year, ‘but the pandemic has slowed production,’ according to Czyzewski.  

Each sign would run an algorithm to process that data and compute the current status of an allocated section of the road and driving conditions. 

As part of this project, the signs are being made so they can be placed on a mobile stand or hung above the road. 

They show updated speed limits which are determined automatically by a mini-computer within the road sign. 

AVS technology is being used to measure motion and pressure changes associated with a sound wave.

This principle, when applied to traffic, can reveal the direction in which a sound wave is travelling and how many sources of sound there are nearby.  

AVS is being combined with Doppler radar, which is based on the principle put forward by 19th century Austrian physicist Christian Doppler.

Smart traffic signs combining Doppler radar and video with acoustic and weather sensors can track traffic volume and alert drivers in real time to hazards ahead 
Illustration of the Doppler effect. Motion changes the frequency of the sound wave based on the direction of motion of its source. This is why ambulance sirens sound lower after they’ve passed us 

The Doppler effect describes the changes in frequency of any kind of sound or light wave produced by a moving source with respect to an observer. 

The effect explains why a car’s horn, for example, sounds lower to us after it passes than when it approached.

Doppler radar systems can provide information regarding the movement of targets as well as their position. 

A Doppler radar system transmits pulses of radio waves, directed at a target, such as a car.

It then measures the difference between the transmitted pulse and a received echo, to ascertain the target’s movement. 

INZNAK road signs will be kitted with both AVS and Doppler radar because both have advantages over the other, according to Czyzewski.

‘Although the acoustical vector sensor – the embodiment of acoustic radar – has lower accuracy than Doppler radar at vehicle counting and isn’t able to measure vehicle speed with the same precision, it has key advantages over Doppler sensors,’ said Czyzewski. 

The main advantages are that AVS doesn’t emit any signals and isn’t susceptible to electromagnetic interference like Doppler sensors are. 

AVS also makes it possible to analyse audio signals to provide an assessment of road conditions – whether it’s wet or dry.   

Cars of the future could use 5G to ‘talk’ to each other

Cars could soon be communicating with each other using 5G to make drivers aware of upcoming hazards, scientists claim. 

The ultra-fast mobile internet would allow for rapid information transmission and could make drivers aware of black ice, pot holes or other dangers up ahead. 

Several car manufacturers are already integrating 5G into their vehicles, including as a tool to help usher in the generation of self-driving vehicles. 

Experts at Glasgow Caledonian University (GCU) believe the high-speed connection will also improve the reliability and capability of automated vehicles to the point where they will be safer than the manual cars being driven today.

They predict the number of road traffic accidents – which according to the World Health Organisation account for more than 1.3 million deaths and up to 50 million people injured worldwide every year – will drop drastically as a result.

Dr Dimitrios Liarokapis, a member of the research group, said: ‘To have a better idea of what the future will look like, think of having Tesla-like cars that not only use sensors to scan what’s around them, they can also talk to each other and exchange safety-related information about their surroundings over an area that covers several square miles.

‘I’m sure anyone who has had a bad experience on frozen roads would have benefited from knowing about the dangerous conditions in advance so they could have adjusted their speed or, if possible, even avoided that route altogether. The same could be said of potholes.’