12Sign display requirements#

12.1Display technology#

The display technology must be light emitting diode (LED). To achieve the required sign luminance levels, the display pixels may be formed by arranging one or more LEDs in a cluster.

12.2LED output#

Each individual LED must be driven with a continuous current with no peak and/or magnitudes exceeding 70% of the LED manufacturer's maximum continuous rating. For LEDs in a 5 mm or smaller diameter package, peak magnitudes of the LED current shall not exceed the manufactured rated driving current.

12.3Character format#

The display of numerals for the purpose of speed regulation and information must comply as much as practicable with the fonts defined in Queensland MUTCD. Numerals must meet the fonts defined for use on a Regulatory Sign R4-1. The annulus must not be less in size than that required for an equivalent static sign. The minimum legibility (sight) distance and character height must be as indicated in the Table 12.3 below for both daytime and night-time viewing.

Refer to traffic control drawings TC1785 1 and 2 for dimensions of the TVSL sign display. Character heights are specified in standard signs R4-1 and vary according to whether 2 or 3 numerals are displayed.

12.4Display changes#

Display changes must be effected by blanking the display, and then activating all required pixels of the new frame simultaneously. Scrolling of images is not permitted. All signs connected to a DP that are instructed to display the same frame must display that frame simultaneously. The sign shall prevent the concurrent display of 2 frames. There must be no discernible flickering of the display. Background flickering as a result of checking the 'on' and 'off' pixel status must not be visible. The display must be able to be reproduced with all required active pixels by camera with shutter speed of up to 1/2000 s. Upon displaying a new frame, the previously displayed frame shall be removed from the sign's memory.

12.5Display colour#

The display must be generated by red and white LEDs on a matte black background. The red and white colours must fall within the chromaticity coordinates specified in AS 5156.

12.6Default display#

Facilities must be included to detect failures within the display control system with the sign defaulting to pre-determined display when major faults are detected. The sign shall blank the display in the event of a sign processor fault. Time to blank shall be a configurable and the range and factory default settings are shown in Appendix A. The sign display must monitor communications with the DP and blank the display if loss of communication experienced. The communications timeout period shall be configurable and the range and factory default settings are shown in Appendix A. The sign shall be able to detect LED failure even if the LEDs may be required to be 'off' at the time of the periodic check. The display must be blanked upon failure of 2% of contiguous pixels for each displayed image or failure of more than 20% of LEDs. Single LED failure, provided that the cumulative LED loss remains below the 2% and/or 20% thresholds described above or TVSL light sensor failure, should not result in blanking of the display.

Loss of power shall result in blanking of the display. On power restoration, the sign shall become available for activation and remain blank until commanded by the DP. At no time shall partial or incomplete frames be displayed.

12.7Red annulus#

The red annulus must consist of suitably constructed, evenly spaced pixel rings in accordance with Table 12.7 below. The number of rings to flash shall be counted from the inner ring. The outer ring(s) shall maintain an apparent solid ring to satisfy the regulatory status of the sign. When displaying the default speed limit, all pixel rings of the annulus must be illuminated.

The annulus shall be constructed so that LEDs connected in series are separated physically by at least 3 LEDs from other circuits.

12.8Flashing display elements#

The sign shall allow selectable flashing of the whole and/or part of the display via all the communications ports. The flash rate parameters must be configurable and also be selectable via all of the communications ports as specified in Appendix A.

12.8.1Flashing partial annulus#

The red annulus must be designed so that the inner rings of the annulus can be flashed as an independent event. In partial flash mode, between 50% and 75% of the total number of annulus pixel rings must flash. The inner diameter pixel ring(s) of the annulus must flash while the remaining outer ring(s) of the annulus must remain lit.

12.8.2Conspicuity devices#

No conspicuity devices or lanterns are required. However, the sign shall allow conspicuity devices to be added in future if desired.

12.9Optical performance#

12.9.1Test procedures#

The optical performance must be determined by measurement under laboratory conditions of the following parameters listed in Tables 12.3 and 12.9.3 below:

• minimum luminance ratio
• minimum and maximum luminance and luminous intensity uniformity
• viewing angle, and
• colour as per AS 5156.

The performance of the TVSL sign displays must meet or exceed the luminance and chromaticity parameters defined in AS 5156. Witness Point 1

12.9.2Luminance#

The luminance of the LEDs, when measured under laboratory conditions, must comply with the requirements of AS 5156.

12.9.3Luminance intensity half angle#

The luminance intensity half angle must comply with Table 12.9.3 below.

12.9.4Sun phantom#

The effect of sunlight or other light sources shining on the optical elements must be controlled such that inactive pixels do not appear active.