Camera-monitor systems instead of mirrors on trucks and buses

A camera-monitor system replaces a mirror with a camera outside the vehicle and a monitor inside the cab. UN Regulation No 46, the UNECE regulation on devices for indirect vision, treats it as one such device alongside mirrors, and Regulation (EU) 2019/2144 lists that UN Regulation for the EU type-approval of motor vehicles of categories M and N, which include buses and trucks. In the version of UN Regulation No 46 published in the EU Official Journal on 8 August 2014, a camera-monitor device may take the place of the close-proximity mirror (Class V) and the front mirror (Class VI). Mercedes-Benz Trucks, DAF, MAN and Volvo describe factory systems that also replace the main and wide-angle mirrors, which DAF names as Classes II and IV. In the United States, 49 CFR 393.80(a) requires every bus, truck and truck-tractor to carry two rear-vision mirrors, one at each side; the Federal Motor Carrier Safety Administration (FMCSA) has allowed camera-monitor systems in their place only through exemptions of up to five years, each limited to one named system.

Status as at 9 November 2026. Read on that day: UN Regulation No 46 as published in the Official Journal of the European Union, L 237 of 8 August 2014, page 24, a text that incorporates all valid text up to Supplement 1 to the 04 series of amendments, whose date of entry into force it gives as 9 October 2014; Regulation (EU) 2019/2144 in its Official Journal text of 16 December 2019; eight FMCSA notices in the Federal Register, from 21 February 2019 to 9 January 2026; and pages and press releases of Daimler Truck, DAF, MAN Truck & Bus, Volvo Trucks, Scania and the supplier Stoneridge. Not among the texts read: the amendments to UN Regulation No 46 after 2014 and the consolidated UNECE text, any later amendment to Annex I of Regulation (EU) 2019/2144, and the text of 49 CFR 393.80 itself, which is quoted here as the FMCSA notices give it.

What a camera-monitor device is

UN Regulation No 46 defines devices for indirect vision as devices “to observe the traffic area adjacent to the vehicle which cannot be observed by direct vision”, and continues: “These can be conventional mirrors, camera-monitors or other devices able to present information about the indirect field of vision to the driver” (paragraph 2.1). In a camera-monitor device for indirect vision the field of vision “is obtained by means of a camera-monitor combination” (paragraph 2.1.2): a camera that renders an image of the outside world and converts it into a signal, and a monitor that converts the signal into images in the visual spectrum (paragraphs 2.1.2.1 and 2.1.2.2).

For camera-monitor devices the Regulation uses a reference object, the critical object, a cylinder 0.50 m high and 0.30 m in diameter (paragraph 2.1.2.6), and the detection distance runs from the centre of the camera lens to the point at which that object “can just be perceived” (paragraph 2.1.2.9). Apart from the design of the device and its attachment to the bodywork, a type of mirror is defined by its class, shape, dimensions and the radius of curvature of its reflecting surface, and a type of camera-monitor device by its detection distance and range of vision (paragraph 2.1.4).

Not every camera on a vehicle is such a device. A surveillance camera-monitor-recording device shows fields of vision other than the ones the Regulation prescribes, or serves as a security system in or around the vehicle (paragraph 2.1.2.13). The Regulation’s provisions do not apply to it, but paragraph 15.3.6 sets where an exterior surveillance camera may sit: at least 2 m above the ground with the vehicle loaded to its maximum technically permissible mass or, if its lower edge is below 2 m, projecting no more than 50 mm beyond the vehicle’s overall width, with radii of curvature of at least 2.5 mm.

The mirror classes a camera stands in for

The Regulation sorts mirrors into classes by the field of vision each must give the driver, set out as a flat portion of road measured from the driver’s ocular points (paragraph 15.2.4). Paragraph 15.2.1.1.1 says these fields “shall be obtained from the minimum number on mandatory mirrors set out in the following table”, and adds: “Where the presence of a mirror is not requested on a mandatory base, this means that no other system for indirect vision can be requested on a mandatory base.”

Two qualifications sit in the paragraphs on the fields of vision. A Class V mirror is not compulsory where its field can be seen through the combination of a Class IV and a Class VI mirror (paragraph 15.2.4.5.5). The front-mirror provisions are compulsory for forward-controlled vehicles of categories N2 over 7.5 t and N3 (paragraph 15.2.4.6.1), but a Class VI mirror is not mandatory if the driver can see, allowing for the A-pillars, a straight line 300 mm in front of the vehicle at a height of 1,200 mm across the width that paragraph 15.2.4.6.2 sets.

The areas beside and in front of a heavy vehicle that these classes cover are the subject of other rules as well: France’s blind-spot signs for heavy vehicles mark them on the bodywork, and London’s permit scheme, which names camera monitoring systems among its measures, is set out in London’s Direct Vision Standard.

What the 2014 text lets a camera replace

Paragraph 15.2.1.1.2 opens two classes to other devices. Where the field of vision of a front mirror and/or a close-proximity mirror “can be obtained by another device for indirect vision that is approved according to paragraph 6.2 of this Regulation and that is installed according to paragraph 15 above, this device can be used instead of the relevant mirror or mirrors.” When that device is a camera and monitor, the monitor “shall exclusively show”:

• the Class V field of vision, where the close-proximity mirror has been replaced;
• the Class VI field of vision, where the front mirror has been replaced, “while the vehicle is moving forward with a speed of up to 10 km/h”;
• both fields at the same time, where both mirrors have been replaced. Moving forward above 10 km/h or reversing, the monitor “may be used for other information, provided that the field of vision prescribed in paragraph 15.2.4.5 below is permanently displayed”, that is, the Class V field.

For the forward-controlled trucks that need a front mirror, the Regulation adds: “If vehicles of these categories cannot fulfil the requirements by using a front mirror or a camera/monitor device, a vision support system shall be used.” That system has to detect an object 50 cm high and 30 cm in diameter within the Class VI field (paragraph 15.2.4.6.1).

The 2014 text has no provision of this kind for the Class II main mirrors or the Class IV wide-angle mirrors; its table lists them as mirrors. In the United States, FMCSA’s notices of 2022 and 2024 describe the European position in their own words: camera-monitor systems “are authorized for use in a number of European countries as a legal alternative to the traditional rear-vision mirrors” under UN Regulation No 46, “which specifies minimum safety, ergonomic, and performance requirements for CMS in place of mandatory inside and outside rearview mirrors for road vehicles. This regulation references ISO (International Organization for Standardization) standard 16505 Rev 2019”. ISO 16505 does not appear in the 2014 text. The amendments of UN Regulation No 46 after 2014 were not among the texts read for this page, so the provisions that FMCSA’s description refers to are not quoted here.

What the device itself must meet

Paragraph 6.2 sets the approval requirements for devices for indirect vision other than mirrors. If the user has to adjust the device, it must be adjustable without tools; a device that covers the prescribed field by scanning must complete scanning, rendering and reset within 2 seconds (paragraphs 6.2.1.1 and 6.2.1.2). For camera-monitor devices:

• Sunlight. “The camera shall function well in conditions in which sunlight falls on the camera.” In a test with simulated sunlight of 40 kLx, the saturated area, where the luminance contrast of a high-contrast pattern falls below 2.0, may cover no more than 15 per cent of the displayed image (paragraph 6.2.2.2.1).
• Monitor. It must render a minimum contrast under various light conditions as specified by ISO 15008:2003, with the luminance contrast measured according to ISO 15008:2009, and its average luminance must be adjustable, manually or automatically, to the ambient conditions (paragraphs 6.2.2.2.2 to 6.2.2.2.4).
• Edges. With the device mounted on a plane surface, parts that a sphere 165 mm in diameter (monitor) or 100 mm in diameter (camera) could touch have a radius of curvature of at least 2.5 mm (paragraph 6.2.2.1.1).

Installed on the vehicle, the device “shall give such performances that a critical object can be observed by the driver over the entire required field of vision” (paragraph 15.3.1), assessed under Annex 10 or, alternatively, by the displayed object size of Annex 11. The obstruction of the driver’s direct view by the device “shall be restricted to a minimum” (paragraph 15.3.2), and “The viewing direction of the monitor shall roughly be the same direction as the one for the main mirror” (paragraph 15.3.4). For Class V and VI camera-monitor devices, the instructions for use must include a table of the minimum and maximum mounting height of the camera above the ground for different viewing distances, and the camera must be mounted within the applicable height range (Annex 11, paragraph 1.4).

How UN Regulation No 46 reaches EU type-approval

Regulation (EU) 2019/2144, the General Safety Regulation, applies from 6 July 2022 (Article 19). Its Annex I lists UN Regulation No 46, “Devices for indirect vision and their installation”, in its 04 series of amendments with the Official Journal reference L 237 of 8 August 2014, page 24, for categories M and N. Article 4(2) states: “Type-approval in accordance with the UN Regulations listed in Annex I shall be considered as EU type-approval in accordance with the requirements of this Regulation and of the delegated acts and implementing acts adopted pursuant to it.” Annex II lists “Indirect vision devices” under UN Regulation No 46 as requirement B13 with date code A: 6 July 2022 as the date for the prohibition of the registration of vehicles, as well as the placing on the market and entry into service of components and separate technical units.

Article 4(3) empowers the Commission to amend Annex I by delegated acts “by introducing and updating references to the UN Regulations, and relevant series of amendments, that apply on a compulsory basis”. Amendments to Annex I were not among the texts read for this page. The Official Journal publication of UN Regulation No 46 carries its own caveat: “Only the original UNECE texts have legal effect under international public law”, and the status and date of entry into force are to be checked in the UNECE status document TRANS/WP.29/343.

The other vision-related requirements of the same Annex II, such as the blind spot information system of requirement B6, and their dates for trucks and buses are set out in mandatory driver assistance systems.

The makers’ systems

The makers’ descriptions include further functions. Daimler Truck’s release of 13 December 2019 says that on the MirrorCam a manoeuvring view switches on with reverse gear and stays on when driving forwards up to ten km/h, that the image on the inside of a bend swivels with a semi-trailer, and that Sideguard Assist shows its warning triangles in the passenger-side display. DAF lists automatic panning for vehicles with a connected (semi-)trailer and display overlays: a red line for the length of the vehicle, a yellow line at 50 metres and a green line at 150 metres. Mercedes-Benz, MAN and Volvo each describe a mode for viewing the surroundings from the cab when the truck is parked. Mercedes-Benz places the cameras on the roof frame and DAF above the cab doors; the cab types themselves are explained in European truck cabs.

DAF and MAN each publish a figure, and the two measure different things. DAF gives its Digital Vision System an improvement in fuel efficiency of 1.2 per cent, “VECTO certified”, and the Corner View 0.3 per cent; MAN says buses with OptiView have “around ten percent less aerodynamic drag than vehicles with conventional mirror systems”. Other aerodynamic claims made for cabs are set out in aerodynamic cabs and length rules, and the way Euro NCAP’s truck rating treats camera monitoring systems in how Euro NCAP tests trucks.

Stoneridge supplies systems for vehicle makers as well. In its renewal application to FMCSA, summarised in the notice of 2 February 2024, it reported that MirrorEye had been installed on over 1,000 vehicles in North America and that in Europe it had been installed on over 1,110 buses and over 2,000 systems had been installed by commercial vehicle original equipment manufacturers.

United States: two mirrors, or an exemption

FMCSA’s notices state the rule: “Section 393.80(a) of the FMCSRs requires that each bus, truck, and truck-tractor be equipped with two rear-vision mirrors, one at each side. The mirrors must be positioned to reflect to the driver a view of the highway to the rear, and the area along both sides of the CMV.” Section 393.80(a) cross-references the National Highway Traffic Safety Administration’s standard FMVSS No. 111, whose paragraph S7.1 covers multipurpose passenger vehicles and trucks with a gross vehicle weight rating above 4,536 kg and below 11,340 kg and buses other than school buses above 4,536 kg, and paragraph S8.1 multipurpose passenger vehicles and trucks of 11,340 kg or more. For commercial motor vehicles with a gross vehicle weight rating of 11,340 kg (25,000 pounds) or more, the 2022 Rosco notice says, FMVSS No. 111 requires a rearview mirror of unit magnification of no less than 323 cm² (50 in²) on each side of the vehicle.

FMCSA may exempt from that rule under 49 U.S.C. 31136(e) and 31315. It decides “whether granting the exemption would likely achieve a level of safety equivalent to, or greater than, the level that would be achieved by the current regulation (49 CFR 381.305)”; an exemption runs for up to five years and may be renewed (49 CFR 381.300(b)). Six camera-monitor systems had been exempted in the notices read.

Each grant is limited to the named system and “does not apply to any other camera-based mirror replacement system/technology”. The conditions changed over time. The grants of 2019 to Stoneridge and of 2020 to Bosch and Mekra Lang forbade continued operation of the vehicle if the camera or monitor failed during normal operation on the highway, until the system could be repaired or mirrors complying with section 393.80 were installed. The grant and renewal notices from 2022 on set conditions instead: drivers inspect the system each time before operating the vehicle and again at the end of each day, noting any defects, and the motor carrier repairs defects noted by the driver before the vehicle is operated again; each of these five notices also has the motor carrier inspect the system periodically. The 2025 renewal for Vision Systems North America also requires motor carriers using the system to report to FMCSA each year the number of vehicles operating under the exemption and any crashes, other than front-end crashes, involving them. The Rosco, Convoy and Safe Fleet notices say that a camera or monitor failure would not lead to an out-of-service order, because it is not a critical inspection item under the Commercial Vehicle Safety Alliance’s out-of-service criteria; the Rosco and Convoy notices add “in the same way conventional mirrors are not out of service if cracked or damaged while in operation”. While an exemption is in effect, no State may enforce a conflicting law with respect to interstate operations under it; States “may, but are not required to, adopt the same exemption with respect to operations in intrastate commerce”.

The 2022 Rosco notice refers to an advance notice of proposed rulemaking on rear visibility that NHTSA published on 10 October 2019 (84 FR 54533); no later NHTSA document was among the texts read. The application by Aumovio SE, which the notice describes as formerly the Continental Automotive division, estimates that, if the exemption is granted, 50 to 100 vehicles with the ProViu Mirror system would be used initially as proof-of-concept or demonstration vehicles with key customers.

Where the rules were read