Functional Limitations Of Traffic Sign Recognition, Detailed Information - GF54.30-P-0021-01A
Model All (CAR)
with code 504 (Speed sign recognition)
Model All (CAR)
with code 513 (Road sign recognition system)
Overview
This document contains information on:
- General
- Function
- Highway entry/exit signs
- Changing traffic signs
- Changing traffic signs without circular ring
- Horizontal angle of vision of multifunction camera
- Resolution of multifunction camera
- Design of back-end sections of commercial vehicles
- Signage on back-end sections of commercial vehicles
General
Speed sign or traffic sign recognition evaluates the information on traffic signs and interprets its meaning. Here, functional restrictions of the traffic sign recognition may occur due to different factors.
Function
Below is a list of situations in which the pictures recorded by the multifunction camera cannot be evaluated and cannot be used for display.
Highway entry/exit signs
Speed limits marked by town/village entry and town/village exit signs or by freeway start and finish signs are not recorded. These traffic signs however, are filed through the road definition feature (e.g. freeway) in the digital navigation map.
Example illustration of highway entry and exit signs
Changing traffic signs
Electronically actuated variable traffic signs may be missed or interpreted incorrectly. In the event of changing traffic signs that are actuated by pulses or flashes, there may be difference to the picture recording's permanent cycle time, depending on the actuated frequency of the changing traffic signs. As a result only fragments of the changing traffic signs will be recognized.
If the image cannot be uniquely identified as a traffic sign, the speed value that is stored in the digital navigation map is then shown.
Example illustration of changing traffic signs
Changing traffic signs without circular ring
To enable the detection of changing traffic signs on which the outer circular ring is missing, special detectors have been implemented in the multifunction camera. This type of display is mainly used in The Netherlands and Belgium.
Example illustration of changing traffic signs without circular ring
Horizontal angle of vision of multifunction camera
The horizontal angle of vision of the multifunction camera is limited.
Traffic signs erected immediately after junctions into which the vehicle is turning may be missed by the multifunction camera.
Example illustration of horizontal angle of vision of multifunction camera
Resolution of multifunction camera
The resolution of the multifunction camera is limited Traffic signs on wide or multilane roads may be missed as they do not attain the size required for clear identification in the evaluation window of the multifunction camera.
The sensitivity and dynamics of the multifunction camera are limited This results in traffic signs not being recognized under the following conditions:
- Traffic signs with low contrast
- Extreme oncoming lights or lights from the rear
- Low levels of lighting darkness The focus and alignment of the multifunction camera 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 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.
Example illustration of resolution of multifunction camera
Design of back-end sections of commercial vehicles
Unfavorably designed back-end sections of commercial vehicles may be interpreted as derestriction signs by mistake.
Example illustration of design of back-end sections of commercial vehicles
Signage on back-end sections of commercial vehicles
Signage on the back-end section of commercial vehicles may be interpreted as traffic signs by mistake.
Example illustration of signage on back-end sections of commercial vehicles