Traffic Sign Assist, function

S54.21-4757-11

S54.30-4602-79

Function requirements for Traffic Sign Assist in general

 Circuit 15R ON

Traffic Sign Assist, general

Traffic Sign Assist is implemented as per the equipment specification in the multifunction camera (MFK) control unit. It can be switched on and off in the "Assistance" menu of the instrument cluster (IC) control unit.

The multifunction camera (MFK) control unit evaluates the following input factors:

 "Engine running" signal.

 Direction of travel, vehicle speed and yaw rate

 Steering wheel angle

 Radio (Audio/COMAND) map data

The multifunction camera (MFK) control unit registers the signposted speed limits, e.g. at the edge of the road, on overhead signs or at construction sites. The recorded picture data are sent to the integrated picture recognition module which compares them against the stored data records and assigns the traffic signs to the respective valid road traffic regulations.

These data are compared with the information from the navigation system and are displayed both in the multifunction display of the instrument cluster (IC) control unit and in the map view of the navigation system according to the country in question. "No passing" zones and the associated derestriction signs are also recorded and displayed. For no-entry zones with corresponding signage, a warning message and a warning tone are also output.

The following traffic signs are registered and evaluated by the multifunction camera (MFK) control unit:

 Speed limits including additional signs along with the corresponding termination signs

 No overtaking signs and their termination

 No entry signs

 Because speed limits are subject to alteration, the digital map data has to be regularly updated.

If the multifunction camera (MFK) control unit does not detect any speed limits (e.g. if the windshield is dirty), the values verified in the navigation system are shown.

If this state persists, the multifunction camera (MFK) control unit changes to "Blocked" mode and the traffic signs display is deactivated. If, later on, a traffic sign is detected again (e.g. reduction in degree of windshield fogging), the "Blocked" mode is deactivated again.

In the event of a fault, the following messages are shown on the multifunction display:

 "System currently not available" (e.g. camera field of view fogged up)

 "System inoperative" (e.g. failure of the multifunction camera (MFK) control unit)

P54.33-3144-71

S54.32-4517-81

The display in the Audio/COMAND display control unit appears only in the map view of the navigation system.

Electronically actuated changing traffic signs
Electronically actuated changing traffic signs can be "missed" or interpreted incorrectly. In the case of changing traffic signs that are actuated in pulses or flashes, there may be a difference between the actuated frequency of the changing traffic sign and the fixed cycle time of the picture recording. As a result only fragments of the changing traffic signs will be recognized.
If the picture cannot be clearly identified as a traffic sign, the speed value that is stored in the navigation system is then shown.

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Electronically actuated changing traffic signs without outer circle
To enable the detection of changing traffic signs with no outer circle, special detectors have been implemented in the multifunction camera (MFK) control unit. This type of display is mainly used in the United Kingdom, the Netherlands and Belgium.

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Horizontal angle of vision of multifunction camera (MFK) control unit
The horizontal angle of vision of the multifunction camera (MFK) control unit is limited. Traffic signs erected immediately after turnoffs may be "overlooked" by the multifunction camera (MFK) control unit.
The horizontal angular coverage of the multifunction camera (MFK) control unit is 46°.

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P54.30-9917-71

The vertical angle of vision of the multifunction camera (MFK) control unit is limited. Traffic signs on overhead gantries are only interpreted reliably up to a vehicle speed of 160 km/h.

In order to keep recognition certainty homogeneous over all vehicle speed ranges, the evaluation window of the multifunction camera(MFK) control unit is downsized as the vehicle speed increases. The consequence of limiting the evaluation window is that traffic signs installed low down are "overlooked" if they are passed at high speed.

Traffic signs on wide or multilane roads
The multifunction camera (MFK) control unit resolution is limited. Traffic signs on wide or multilane roads can be "missed" as they do not reach the size required for clear identification in the evaluation window of the multifunction camera (MFK) control unit.

P54.30-9846-71

The sensitivity and dynamics of the multifunction camera (MFK) control unit is limited. This results in traffic signs not being recognized under the following conditions:

 Traffic signs with low contrast

 Strong oncoming lights or lights from behind

 Low levels of lighting, darkness

The focus and alignment of the multifunction camera (MFK) control unit are fixed. As a result recorded objects are represented with a movement blur depending on the exposure time.

This movement blur and sensitivity of the multifunction camera (MFK) control unit limit its usefulness at night. The result of the fixed focus and static alignment is that the traffic signs to be recorded must be completely visible in a small observation time window.

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P54.30-9848-71

Unfavorably designed back-end sections of commercial vehicles may be interpreted as derestriction signs by mistake (left picture).

Signage on the back-end section of commercial vehicles may be interpreted as traffic signs by mistake (right picture).

 Navigation system data are not available during an update or reset procedure for the radio (Audio/COMAND), which may lead to fault messages occurring in some cases.