The difference between driving with a camera monitor system and mirrors

Driving trucks with side mirrors has always been something that drivers have taken for granted. In recent years though, several manufacturers have started to offer camera monitor systems instead. But when and where can that be useful, and what are the pros and cons of a camera versus a mirror?

In 2016, United Nations opened for a regulation that allowed camera monitor systems to replace mirrors. One of the benefits was that the so-called direct vision improved, which means the visibility from the driver's point of view: namely, that which can be seen without the aid of mirrors or cameras.

The European Commission estimates that the coming General Safety Regulation will reduce the number of accidents and hopefully save over 25,000 lives and avoid at least 140,000 serious injuries by 2038. Camera monitor systems can contribute to these numbers as they improve direct vision.But the main reason behind the development of camera monitor systems has been better aerodynamics and the possibility of saving fuel and CO2 emissions.

“Everyone wants to improve their fuel or energy consumption, and with reduced air resistance from mirrors, more slender camera units can improve energy efficiency with up to 1.5%*. But it’s also important to see which solution fits the customer and improves their driving experience”, says Gabor Szalo, Senior Engineering Specialist in Visibility at Volvo Trucks.

The first truck with cameras instead of side mirrors came in 2019 and the technical possibilities have been developing rapidly since then. Several manufacturers have been releasing trucks with camera monitor systems and the incentive from future legislation is speeding up the process. By 2029, the European General Safety Regulation  (GSR), will implement direct vision requirements for all newly registered trucks to minimize blind spots and improve what drivers can see directly from their vehicles.

Setting technical developments and upcoming legislation aside, there are possibilities and benefits, as well as challenges and limitations, driving with cameras instead of mirrors. Here are some of the aspects that can be considered:

The benefits of driving with a camera monitor system vs side mirrors

Aerodynamics:

• A truck’s aerodynamics have one of the biggest direct influences on fuel efficiency and, in turn, environmental impact. Since camera monitor systems are lowering the impact of air resistance compared to traditional side mirrors, they will reduce both fuel and energy consumption.
  
  

Visibility and safety:

• With a camera, there are no physical mirrors blocking your sight as a driver. Therefore, it is suitable for complex traffic situations: for example, when vulnerable road users are close to the truck or in roundabouts where the mirrors might obstruct the driver’s visibility.
• There can also be automatic or manual trailer tracking in the cameras to be able to follow trailer movements or for use when reversing. These are digital benefits that are not possible with a side mirror.
• Built-in reference lines (when changing lanes) can be another form of digital support with a camera monitor system.
• With ordinary convex mirrors there is some image distortion, due to the mirror radius. For a camera monitor system, there are possibilities to correct the image distortion, so drivers can get an image closer to reality.
• When the driver is sleeping, there can be surveillance features with a camera monitor system. It can also be activated from inside the cab, without having to draw back the curtains.
   

Weather and darkness:

• A camera generally offers a better vision during rain since the lens can be better protected inside the camera arm. But perhaps more importantly, the screen is situated inside the cab, improving the visibility compared to when there is rain both on the window and on the mirror itself.
• It’s easier to keep a camera lens clean than with a traditional mirror with a bigger glass area. The camera is also generally placed higher on the outside truck exterior, making it less susceptible to dirt.
• In darkness cameras can offer the benefit of better visibility compared to mirrors and also enhanced night vision, due to a camera’s ability to operate in low light conditions.
   

Legal compliance:

• As mentioned earlier, since there are legal requirements for direct vision in the General Safety Regulation (GSR) 1929, a camera monitor system could offer a preferable option.
• Vehicles over 12 metric tons passing through London from 2024 must have a three-star rating (based on what drivers can see directly from the cab windows) or fit their trucks with a range of safety systems. This makes trucks with cameras, replacing mirrors a preferable choice.
  
  

The challenges of driving with a camera monitor system vs side mirrors

Visibility and safety:

• Mirrors provide a three-dimensional image while camera systems are two-dimensional. Depth vision, assessment of distance and speed of vehicles from behind can require some time to get used to.
• The resolution of the camera can be a disadvantage compared to a mirror. Mirrors offer the same level of sharpness as your eyes have. Cameras have a wide-angle lens and a screen with limited resolution. This might make it harder for drivers to judge distance. The choice of image resolution and screen size are therefore important factors.
• The placement of the screens must be adapted to fit the cab interior to avoid creating another blind spot. It can result in smaller screen size than ordinary mirrors, which consequently impacts the object sizes in the screen.
   

Repairs:

• There are both sensors and screens in a camera monitor system, based on a computer managing the image. Any potential damage could be more costly to repair. But it depends on which component that needs to be replaced, or if it is covered in a service agreement.
   

Driving experience:

• Looking at a two-dimensional image on a camera screen is different than looking into your regular mirrors. More drivers are currently used to driving with classical side mirrors, making this a new driving experience and something to adapt to.
• Another thing to get used to, but more importantly, that needs to be learned, is the technical settings and new features. These are to be incorporated in the driver’s daily routine, when learning how to maneuver, as well as correctly estimating speed, distances, and surrounding areas.
  
  

How to choose - The future of the side mirrors and camera monitor systems

Both camera monitor systems and traditional mirrors have their advantages and drawbacks. The driving experience with side mirrors versus a camera monitor system is different, and there are also likely to be different preferences held by drivers.

Some segments might also find it easier to adapt: For example, within long haul, one can potentially get used to it faster than those who drive a lot inside cities where repeatedly judging distances and evaluating the depth of vision is crucial, and where more reversing may be necessary.

“Preferences can vary, the goal with cameras is to get the screen as close to reality as possible, to offer the best driving experience possible. For new drivers, cameras might be the standard and your choice can also depend on how open you are to changes and new digital solutions in the driving environment”, says Hanna Degerman, User Experience Product Planner at Volvo Trucks.

Kjell Brunnström is a senior scientist at RISE Research Institutes of Sweden, specializing in visual perception. He believes cameras can be more common and favored in the near future, but it can also be beneficial to add some aspects to the camera monitor systems to be able to make them a preferred option for everyone and every segment in the transport industry.

“As it is now, camera monitor systems give a reduced depth of vision compared to regular side or rear-view mirrors. But a study conducted at RISE and Volvo Cars** showed that to mitigate the reduced depth perception, the cameras should preferably present additional graphics, indicating distance and dangerous objects, which could help the driver make the correct decisions.”

Technology has been evolving fast within this area. Your choice between a classic side mirror or a camera monitor system might depend on preference or segment. There’s a need to evaluate your business requirements but also possibilities for legal compliance: and perhaps also your driver’s preference for, and openness to new driving experiences.

*Actual energy economy may vary depending on many factors i.e. driving speed, use of cruise control, vehicle specification, vehicle load, actual topography, the driver´s driving experience, vehicle maintenance, and weather conditions.

** Source: Zhang, M. and G. Bin. The effect of CMS with AR on driving performance. (diva2:1717225), RISE Research Institutes of Sweden, Chalmers University of Technology, M.Sc. thesis. 2022, Available from: http://urn.kb.se/resolve?urn=urn:nbn:se:ri:diva-61469