More and more Actros and Arocs trucks are showing up on the road without the conventional large external rearview mirrors. Instead, small aerodynamically shaped camera arms are mounted on the roof frame. Since June 2019, Mercedes‑Benz has been delivering its heavy‑duty trucks fitted with MirrorCam – a world first, and the one and only truck manufacturer to do so. In most of the European markets, the Actros with the L cab comes with MirrorCam fitted as standard fare.

Not only do the digital rearview mirrors have a futuristic look; they also reduce fuel consumption by up to 1.3 per cent thanks to their aerodynamic advantages. Even more importantly, the system has a lot more to offer in terms of safety than conventional main and wide‑angle mirrors. The performance of MirrorCam exceeds legal requirements by far.

Patrick Hirth is a mechanical engineer in the driver cab development section at Daimler Truck AG, and he has already covered over 200,000 kilometres on the road with the new MirrorCam. He says: “After a short acclimatisation phase, the driver becomes acutely aware of the advantages offered by MirrorCam in many different situations. Overtaking, manoeuvring, driving in poor visibility and cornering – all this can now be done more safely and without stress.”

The MirrorCam system incorporates two cameras, one each mounted on the left and right side of the roof frame. To protect them from getting damaged, they are hinged so that they can be folded forward or backward. There are two portrait‑format display monitors mounted on the A‑pillars in the driver’s cab, and operating elements are fitted in the door module as well as on the Multi‑Touch‑Display. In addition, there is a switch on the passenger side to turn on MirrorCam when the engine is turned off, and optionally also another one in the bunk. The images recorded by the cameras are sent to the two 15.2‑inch monitors with a resolution of 720×1,920 pixels. As with a conventional mirror setup, the image on the monitors is split into a main and a wide‑angle area.

“The fact that the cameras of the MirrorCam system are fitted to the roof frame, with the monitors mounted inside the driver’s cab, means the driver has a much better direct view out of the side windows,” explains Dirk Stranz, a development engineer at Daimler AG. “The line‑of‑sight diagonally forward is clear, whereas the large exterior mirrors tended to obstruct the driver’s view in many situations. This is particularly important when a pproaching crossings and roundabouts, when manoeuvring, and in tight bends.”

MirrorCam also assists the driver when manoeuvring in reverse: the display will then switch to a special manoeuvring view. This makes reverse cornering easier because even more distant areas around the vehicle are displayed in proportionate size. The manoeuvring view is activated automatically when reverse gear is engaged and then remains active even when driving forwards up to a speed of ten kilometres per hour, or until deactivated with the push of a button.

“The distance lines on the MirrorCam display also provide useful support,” says Dirk Stranz. “They help the driver to better assess the distances to objects behind his own vehicle in relation to the current driving situation. During overtaking manoeuvres, the red, orange and yellow markings on the MirrorCam display on the right indicate whether the truck can already switch back to the right‑hand lane safely, or whether there are still a few metres to go before the required safety distance has been reached.”

It is important, however, that the driver sets the adjustable distance line on the door‑mounted control panel before setting off, so that the line accurately shows him the rear end of his own vehicle on the display. “To do that, I always place my hi‑viz vest on the ground next to the rear end of the trailer, and then adjust the distance line using the vest as a reference before I drive off,” explains test driver Hirth. Another useful plus is that whenever trailers have been switched, the system warns the driver before the start of the journey by flashing the line. This allows the driver to check whether the length of the overall rig is different with the new trailer.

One particular feature of MirrorCam comes to the fore when the articulated vehicle drives around bends: the image on the display showing the inside of the bend pans along, so that the driver can maintain a clear view of the end of the trailer at all times. With a conventional mirror system, on the other hand, the mirror on the inside of the bend often only shows the trailer’s side wall, due to the angle at which the semitrailer is travelling. “It has actually happened to me that I brushed against a tree branch with the rear end of the trailer,” admits Patrick Hirth. “With MirrorCam there is much less risk of making contact with an obstacle.” The system is set up for standard trailers in general, but the panning action can be adjusted individually. This happens automatically with modern trailers, as they are designed to send their geometry data to the tractor unit. The driver can manually adjust the panning radius in the door‑mounted control panel, using the side selection button and the cross rocker.

Another plus in terms of safety: on the Actros and the Arocs, MirrorCam and Sideguard Assist* work hand‑in‑hand. The Sideguard Assist system comes to the aid of the driver in hazardous situations when turning right. Sideguard Assist will give visual and acoustic alarms whenever there is a risk of collision with a stationary or moving object within the alert zone on the right‑hand side of the truck: a yellow triangle is displayed on the monitor of MirrorCam on the passenger side, followed by a red triangle. Alert signals will also be sounded.

This allows the driver to still brake in time if he has failed to notice something on the passenger side before turning right. This represents a distinct advantage, especially in dense city traffic where there are many cyclists, pedestrians, e‑scooters and parked cars. But that is not all: Sideguard Assist also functions as a lane‑change assist system for the right‑hand side and alerts the driver, again with a yellow or red triangle on the MirrorCam monitor, if there is another road user in the lane to the right of truck.

MirrorCam offers yet another benefit compared to the conventional mirror system: many drivers unintentionally drive with mirrors that are not optimally adjusted. This can result in a dangerous “blind spot” on the passenger side: an area where other road users can easily “disappear”. Sometimes all it takes is a slight change in seating position for the driver to create a “blind spot” on the passenger side. This is because with a conventional mirror, the formula “angle of incidence equals angle of reflection” consistently applies to the driver’s line of vision.

With MirrorCam and Sideguard Assist, this problem goes away: “blind spots” are a thing of the past, because the monitors will always show the same image from the camera – regardless of the angle from which the driver is viewing the monitor. 

* Currently available in LHD only.

Even when the driver takes a break, MirrorCam still offers a great advantage: with the engine turned off, the system can still be activated for two minutes at a time via a switch on the passenger side, or via an optional switch in the bunk. “This function is a very convenient added safety feature for us drivers, because it means we can take a look around the vehicle at any time, without anyone on the outside being aware of it,” says Patrick Hirth. “For example, if thieves should try to get at the fuel tank or at the load, I can see it even if the curtain is closed and raise the alarm.”

Last but not least, the fact that the camera arms are hinged and can be folded in both directions minimises any potential damage in the event of a collision. The smaller size and the high positioning of the cameras alone also lowers the risk of hooking onto some obstacles considerably. Another benefit in the event that the vehicle will be sold at a later stage: trucks that come with MirrorCam can be retrofitted with conventional mirrors using installation points already provided in the door body shell.

Can dirt and rain negatively affect the images provided by MirrorCam?

When it comes to dirty mirrors and condensation on windows, the MirrorCam system has numerous advantages compared to conventional rearview mirrors. Thanks to the position of the cameras high up on the vehicle, the small cover extending over the camera lens, a special coating and the digital transmission of the image to a display in the driver’s cab, fogging and dirt have virtually no impact on the performance of the system. Equally useful on cold and humid days is MirrorCam’s heating system, which kicks in automatically at temperatures below 15 degrees Celsius.

Many users have complained about noise degradation of the image at night. Is the camera system at a disadvantage compared to a conventional mirror system at dusk or dawn, or at night?

No. In fact, MirrorCam performs better in residual light situations, that is, at dawn or dusk. The cameras are designed to be very light‑sensitive. This allows the monitors to display a brighter image than what is actually out there. This provides the driver with more visual information about the surroundings than a normal mirror would. In addition, the brightness of the image automatically adjusts to the ambient light continually – preventing the driver from being blinded by bright lights. All of this works equally well on the open road and inside tunnels. Of course, in total darkness MirrorCam will also be able to depict only those areas that are illuminated by the vehicle itself. But that is no different with conventional mirrors. With MirrorCam, our development team tuned the system in such a way that it provides as much visual information as possible, and right now this does still produce a slightly noisy image

Speaking of image quality: why is the picture on the monitors not as sharp as on my smartphone?

In the development team, we see the established viewing habits of drivers as more important than pixel density: with the large monitors measuring 15.2 inches diagonally, the displays of the MirrorCam roughly correspond to the conventional shape of mirrors. This allows drivers to estimate the distance and speed of a following vehicle by the size and the change in size, just as they have always done. It’s true that many smartphone displays have an insanely good resolution, but there you hold the device in your hand, the distance from the eyes is small, and the monitor is small, so this is a bit like comparing apples with pears. The MirrorCam displays, by comparison, are much further away, and the greater the distance, the less detail our eyes can make out. Which means, in my view, that it is simply not necessary for MirrorCam to have the pixel density of a smartphone. The other important thing to note is that MirrorCam represents a key safety system, and for this reason it has been designed for utmost reliability. It has successfully passed all the prescribed approval procedures. Given the current state of the technology, a smartphone would fail those tests.

Can the brightness of the display be adjusted if I find it dazzling?

Yes, differences in the light sensitivity of drivers sharing a vehicle, changing weather conditions and times of day – there are sometimes valid reasons to readjust the brightness of the displays. The driver can do this easily via the Multi‑Touch‑Display or via the multifunction steering wheel. They can even have different brightness settings for the monitors on the left and the right. There is a virtual sliding ruler under the menus “Information display and Brightness”, “Display Brightness”, “MirrorCam”.

How do drivers wearing spectacles cope with the displays, and are drivers allowed to wear sunglasses

The MirrorCam displays are easy to view for people wearing glasses, too. A particular benefit for drivers wearing glasses is that the positioning of the displays on the A-pillars means that they no longer have to look so far to the left and right in order to see the traffic behind – there is therefore less interference from the spectacle frame. It can happen, however, that drivers wearing glasses struggle a bit getting used to the changed viewing angles and distances. The first thing to check would then be: is the prescription for the glasses still correct for their eyes? Changes in our vision tend to be very gradual, which is why most people are not even aware of them at first. If long-established habits – like looking in the rearview mirror – then need to be adjusted, it is easy to jump to the conclusion that there is something wrong with the system. But in fact, the problems of getting used to the system are often due to glasses that are no longer suitable for the driver’s eyesight. Be it at the desk or behind the wheel, the hard and fast rule is that the glasses must be appropriate for the workplace! Driving with sunglasses is usually not a problem. A great deal depends on the optical quality of the lenses, however, the degree to which they change what we see. Sunglasses always come with both advantages and disadvantages – whether we use mirrors or the MirrorCam system.

Why do many drivers find it difficult at first to reverse in a straight line using MirrorCam?

I am familiar with this phenomenon – it is one that resolves itself after a short period of getting accustomed to it, provided the system is used as intended. What is happening here is this: MirrorCam provides two separate views when manoeuvring in reverse. By default, the large main display shows the area close to the truck, and the lower part shows the wider, most distant surroundings. This split view is particularly useful when the driver is driving backwards around a bend. But if the driver only reverses the vehicle in a straight line, it is often better to deactivate this function. That can be done quickly and easily via a button in the door-mounted control panel. So you see, manoeuvring with MirrorCam offers more options compared with using conventional mirrors. Another thing to get used to at first is that when reversing in a straight line, the driver can actually see more of the vehicle than with conventional mirrors. This is because the cameras are set a bit further away from the vehicle than mirrors. This is also something to get used to. The best way to get accustomed to it is to watch both displays, alternating between them. If you only look at one of the displays the whole time, you sometimes get the impression that you are driving at an angle, even though you are driving straight as a die.

Mr Stranz, thank you very much for this interview!