Creating driver-aware apps – The value of MirrorLink application certification

The MirrorLink Application Certification program provides a clear, vendor-neutral path to designing apps that meet driver-distraction guidelines and therefore can be used responsibly while driving. Because a large number of MirrorLink-enabled cars and MirrorLink-enabled handsets are already in use, a substantial market for these driver-aware MirrorLink apps exists today. There are two levels of application certification: and . MirrorLink Base Certification verifies interoperability with MirrorLink smartphones and (IVI) systems, and ensures the app can be used while the car is parked. MirrorLink Drive Certification ensures apps can be used while the car is moving; the primary goal is that apps do not distract drivers. When designing driver-aware apps, developers need to consider requirements aimed at avoiding , including restricted content, visual contrast, and text and button size. Because driver distraction is a safety issue, testing at a MirrorLink Authorized Test Lab is required to achieve application certification. Apps can obtain Regional or Global Drive Certification; in the vast majority of cases, Regional Drive Certification will be sufficient to cover all the markets targeted by an app.

Driver distraction is a critical safety concern when using technology in cars. Distraction is anything that diverts the driver’s attention from the primary tasks of navigating the vehicle and responding to critical events [1]. Because distracted drivers may miss vital events and road cues, distraction can quickly lead to dangerous situations. At 80 km/h, a vehicle travels more than 22 meters during each second that a driver takes his or her eyes off the road.

To minimize the risk of distracted driving, technology use should always be secondary to the primary task of driving, and should require a minimum of attention from the driver. However, apps are generally not designed with this aim in mind. In fact, the opposite is usually true: the implicit assumption is that the user’s primary focus is on the smartphone app, and controlling the app typically requires the user’s full attention.

To enable responsible use of smartphone apps in moving cars, drivers must be able to interact with them in a way that minimizes the attention required. MirrorLink Drive Certification for apps is designed to achieve this goal. It provides a clear path for developers to design apps that can be used while driving. This opens up a major new market for developers: the .

MirrorLink is the leading industry standard for car-smartphone connectivity. A large number of MirrorLink-enabled cars are already on the road, from companies including Honda, Peugeot, Citroën, Toyota, Volkswagen, and Skoda. Even more MirrorLink-enabled smartphones, from manufacturers such as , Samsung, Sony, and LG, are being used by consumersi.

MirrorLink enables users to stay connected to their smartphone apps even while driving. With MirrorLink, apps run on any compliant smartphone and drivers interact with them via any compliant IVI system, also known as a head unit. The applications on the smartphone project their (UI) to the IVI display and stream audio via the car’s speakers. Drivers interact only with the head unit and other car controls while the smartphone is stored away, as shown in Figure 1.


Figure 1: MirrorLink, leveraging the vehicle’s accessible display and controls [9].
(Click graphic to zoom by 1.9x)

MirrorLink handles the communications between smartphone and IVI, allowing developers to focus on creating innovative content and user interfaces [2]. MirrorLink has been designed to minimize the burden on developers: app developers do not need to learn a new SDK, just a thin API that is used to obtain information and events.

MirrorLink Drive Certification is an application certification program that ensures apps comply with industry-accepted driver distraction guidelines. These guidelines are based on principles developed by industry associations for use by automotive experts. The MirrorLink Drive certification requirements translate the information into a much shorter requirements document that focuses only on the aspects directly relevant to apps, and explains them in terms that can be easily understood by developers.

App certification is required because driver distraction is a safety-critical issue. To achieve certification, apps undergo testing by a MirrorLink Authorized Test Labii. Once Drive Certified, apps are available to drivers via MirrorLink IVIs and smartphones even while the car is moving. In contrast, apps that are not Drive Certified are blocked and therefore unavailable to the driver via the IVI. Certified apps become part of a trusted ecosystem of MirrorLink software and hardware, and benefit from MirrorLink branding and exposure to a broader audience.

Developing and certifying MirrorLink apps

There are two levels of certification: Base Certification and Drive Certification. This article provides descriptive information about some of the key certification requirements. The complete, definitive set of Base and Drive Certification requirements is provided in the corresponding requirements documents [3, 4].

Base Certification

Base Certification is required for all apps and is a pre-condition for Drive Certification. Base Certification validates that apps work with any MirrorLink-certified device, and ensures that the driver can use and interact with the app through any MirrorLink-enabled IVI. MirrorLink IVIs must make Base Certified apps available to the user while the car is parked by presenting the certified apps in the IVI’s app list.

Drive Certification

Drive Certification is additionally required for apps used while driving. The primary goal is that apps do not distract drivers. Drive Certification ensures apps can be used via MirrorLink IVIs while the car is moving; MirrorLink IVIs must make Drive Certified apps available while driving.

Base Certification

The goal of Base Certification is to verify that the app works with any MirrorLink device, including IVIs and smartphones. A key requirement is that the user must be able to interact with the app using the controls available on IVIs, which may differ from those available on smartphones. Apps use the MirrorLink Common API for some functions, including querying the connected IVI to obtain information such as the manufacturer, the controls available, and the screen size and resolution [5].

IVI controls and user input

Because the controls on IVIs differ from those available on smartphones, some current practices in smartphone app UI design do not apply to the MirrorLink environment. Developers creating MirrorLink apps should therefore take extra care to plan for these differences.

One key difference is that some cars and IVIs, including models from Mercedes-Benz, lack a touch-sensitive screen. Instead, the user interacts with the app via a (Figure 2). Apps must accept input from rotary knobs as well as touchscreens.


Figure 2: Example rotary knob controller [8].
(Click graphic to zoom by 1.9x)

The knob supports seven input operations: push; rotate clockwise and counterclockwise; and shift left, right, up or down, as shown in Figure 3. A knob may also provide additional diagonal shift operations or other selected hard buttons.


Figure 3: Rotary knob controller operations [3].
(Click graphic to zoom by 1.9x)

Rotary knob-based interfaces work in a different way from touch-based interfaces. With touch-based interfaces, the user can immediately activate any of the visible control elements simply by touching them. With rotary knob-based interfaces, the user must first move the focus to an individual control element using the knob’s shift or rotate operations, then activate that control element, typically with a push operation. Therefore, in contrast to touch-based interfaces, rotary knob-based interfaces must show which control element is the current focus (Figure 4b).


Figure 4: Example of (a) non-focus user interface for touch control (left) vs. (b) focus user interface for rotary knob control (right) [10].
(Click graphic to zoom by 1.9x)

All main app functionality must be available via the rotary knob, including the ability to select and activate functions and areas of focus within the app. Exceptions are specific operations that would be extremely complex to perform with a rotary knob, such as selecting a random point on a map.

Even among IVIs with a touchscreen, multi-touch support is not yet widespread. Therefore the app must not require multi-touch operations, although it may optionally take advantage of multi-touch if the IVI supports it.

The app may accept voice input if that is also supported by the IVI and smartphone.


Apps that produce audio must be able to stop their audio stream when necessary so that the user can hear higher priority audio content. For example, a music app must silence or pause its music stream when the user receives an incoming phone call or a voice prompt from the navigation system. These events are made available to the app via the Common API.

Drive Certification

MirrorLink Drive Certification validates that the application can be used without interfering with the safe operation of a vehicle. Accordingly, the requirements for Drive Certification focus mainly on preventing driver distraction and ensuring application functions are easily accessible while driving.

Restricted content

The app must not display any content that could reflexively draw the driver’s attention away from the road. This includes video-based entertainment, animated graphics used for entertainment, flashing content, or scrolling text. Visual advertisements are allowed, provided they are compliant with all other requirements. Apps that are running in the background must not display popups or visual notifications because they might distract the driver. Exceptions include incoming phone calls and drive-related notifications such as navigation prompts.

Visual accessibility

Visual accessibility requirements are designed to make sure that the display is easily read and comprehended by the driver. Focus areas include contrast and text formatting.


Drivers must be able to read the IVI display even in sunlit conditions. Because of this requirement, MirrorLink apps must provide a higher level of contrast than apps used on handheld smartphones. If the display of a handheld smartphone becomes hard to see due to bright sunlight, users can simply move into the shadows. But when driving, users don’t have that option; therefore greater contrast is required to ensure the display can be easily seen, even in sunlight.

It is important to consider these contrast requirements during app design. MirrorLink requires a contrast ratio between foreground elements such as text and symbols and their immediate background of 7:1, based on a scale of 1:1 to 21:1 [6], with the goal of ensuring adequate contrast while providing developers with design flexibility.


Figure 5: For MirrorLink Drive Certification, the contrast between button text or symbols and the button background must be at least 7:1 [9].
(Click graphic to zoom by 1.9x)

The contrast ratio for interactive elements (Figure 6a) is measured between the button text/symbol and the button background. There is no requirement for the level of contrast between the button background and the overall application background. The contrast ratio for text and symbols (Figure 6b) is measured against the immediate background color.


Figure 6: Contrast ratio for (a) interactive elements (left) and (b) text and symbols (right) [9].
(Click graphic to zoom by 1.9x)

Online tools are available to quickly determine whether a specific color combination meets requirements; the MSF&W Color Contrast Ratio Calculator [7] shows good and unacceptable combinations.

Fonts and text size

Primary text must be at least 4.2 mm high when viewed on the MirrorLink display used in testing, which is positioned at a maximum distance of 90 cm from the driver’s eye. The reference display in Figure 7 is 13.33 cm wide and 8 cm high, providing a resolution of 800 x 480 pixels.


Figure 7: Because an IVI display is much farther from the user’s eye than a smartphone screen, text must be correspondingly larger to occupy the same angle of view so the driver can read it with a quick glance [9].
(Click graphic to zoom by 1.9x)

The minimum size of 4.2 mm is much larger than the text typically displayed on smartphone screens. Because the IVI display is much farther from the user’s eyes than a handheld smartphone, text must be correspondingly larger to occupy the same angle of view so that it can be easily read with a quick glance. The minimum text size is based on the specification for text legibility defined in ISO 15008. Supplemental text may be smaller (at least 3.2 mm), and there is no size requirement for some types of text-based information, such as map information. It is, however, recommended to choose font properties that make the text clearly legible within maps.

Developers can choose from a wide range of fonts that are pre-approved by the CCC and listed in the Drive Certification requirements, or use other fonts that comply with guidelines described in the requirements.

Manual accessibility and controls

To avoid distraction, the driver must be able to easily and quickly interact with the app while the car is moving.


Figure 8: Not-allowed (a, left) and allowed (b, right) button designs [9].
(Click graphic to zoom by 1.9x)

Buttons and other controls displayed on IVI touchscreens must be much larger than on smartphones so that the user can easily locate them with a glance and operate them with a finger on a screen an arm’s length away – even when road-induced vibration makes precise movements difficult. They must be at least 10 mm along their shortest edge and occupy at least 50 percent of a 200 mm2 horizontally aligned rectangle (see Figure 8 for allowed and not-allowed examples).

Some IVIs use resistive touchscreens, which are less sensitive at the edge of the screen than at the center. Because of this, each button must be positioned so that more than 50 percent of its active area is within a threshold located 5 percent of the screen’s width away from the screen’s edge, as shown in Figure 9.

The user must be able to complete all tasks with one hand.


Figure 9: Locating buttons within the 5 percent threshold on touchscreens [4].
(Click graphic to zoom by 1.9x)

Pace of interaction

To avoid distracting users from their primary task of driving, apps must not put the driver under pressure to respond to prompts or dialog boxes within a specific time. Users should be able to interact with the app at their own pace. For example, drivers may need to suspend their interaction with an app in mid-operation while they maneuver to avoid a road hazard. No matter how long that interaction is suspended, a driver should be able to return to the app at any time and continue from the same point.

This means applications must not automatically time out. Dialog boxes should be left on screen until the driver has completed or dismissed them. If the user temporarily suspends a task, such as navigating a menu or entering a phone number, the app should preserve the user’s progress until he or she returns to the task.

Apps should respond quickly and noticeably to user input, so that users can quickly return their focus to the task of driving.

Geographic considerations

Base Certification is valid worldwide, but there are regional differences to consider when seeking Drive Certification. Apps can be Drive Certified for specific regions or for global use.

The regional certifications are as follows:

  • Default (valid worldwide except in EU member states, Canada, United States, and Japan)
  • EU (valid worldwide except in US, Canada, and Japan)
  • US and Canada (valid worldwide except in Japan)
  • Japan (valid in Default region and Japan)

It is important to note that, in the vast majority of cases, one of the regional certifications will be sufficient to cover all the markets targeted by an app. This is because the North America and EU certifications are valid in many other parts of the world. An app that is EU Drive Certified can be used in Korea, for example. Developers therefore never need to undergo both NA and EU certification; they simply need to choose which of the two regional certifications best meets their needs. Global certification imposes a much more restrictive set of requirements because global guidelines combine the restrictions of all regions.

Also, the fact that Base certification is a prerequisite ensures that apps certified for this region work with MirrorLink devices. Japan has some unique requirements, and therefore apps certified for Japan are limited to use in that country and the Default region.

Regional Drive Certification requirements differ primarily in the level of testing required. Certification for the US and for Japan requires region-specific workload verification testing. This involves testing by human participants to verify that app tasks can be completed with short glances at the screen, i.e. that users do not take their eyes off the road for more than a specific length of time. Default and EU regional certifications do not require workload verification.


MirrorLink Drive Certification opens up a fast-growing new market for app developers: the connected car. It provides a clear, vendor-neutral path to developing applications that meet driver distraction guidelines, and therefore can be used responsibly while driving. Because a large number of MirrorLink-enabled cars and MirrorLink handsets are already in use, a substantial market for these driver-aware MirrorLink apps exists today.

Dr. Jörg Brakensiek is Chief Architect at the Car Connectivity Consortium (CCC),

Christopher Seubert is Chair of the User Experience Working Group at the Car Connectivity Consortium (CCC), and an automotive software engineer at Carmeq GmbH.


Car Connectivity Consortium (CCC)


[1] US National Highway Traffic Safety Administration

[2] Developing Apps for the Connected Car: An Introduction to MirrorLink. Car Connectivity Consortium 2014

[3] Car Connectivity Consortium MirrorLink Application Requirements for Base Certification

[4] Car Connectivity Consortium MirrorLink Application Requirements for Drive Certification

[5] Available at the MirrorLink Developer Portal.

[6] As discussed in W3C Web Content Accessibility Guidelines 2.0

[7] MSF&W Color Contrast Ratio Calculator,

[8] Mercedes-Benz C-Class 2014: COMAND Controller and Touchpad in the centre console, Exclusiv Line, interior;

[9] Car Connectivity Consortium,

[10] Glympse,

i. A list of MirrorLink certified products is at

ii. A list of Authorized Test Labs is available at