11Variable message display requirements#

11.1General#

The variable message display technology shall be light emitting diode (LED). The display pixels may be formed by arranging one or more LEDs in a cluster to achieve the required luminance levels. The displays shall use a series of pixels forming a dot matrix display system. A 'full matrix' configuration shall be used to allow the display of graphics as well as alphanumeric characters. The horizontal and vertical pitch of the pixels in the matrix shall be in accordance with AS 4852.2. The variable message display pixels shall be in modules of a size capable of being removed and installed by hand via access door(s) or screen. The permissible TVMS message types shall be as described in Clause 9.2.

11.2Failures#

Facilities shall be included to detect failures within the display control system. The DU shall blank the display in the event of a sign processor fault. Time to blank shall be a configurable setting. The DU shall monitor communications with the TVMS controller and blank the displays if loss of communication is experienced. The communications timeout period shall be a configurable setting. The TVMS controller shall be able to detect LED failure even if the LEDs is required to be ‘off’ at the time of the periodic check. The display shall be blanked upon failure of 2% of contiguous pixels for each displayed image or failure of more than 20% of LEDs. On power restoration after loss of power, the TVMS shall become available for activation and remain blank until commanded by the TVMS controller or STREAMS. The power recovery delay time shall be configurable. At no time shall partial or incomplete messages be displayed. The TVMS controller shall allow the sign's display to remain blank for a minimum time once the display has been blanked irrespective of the cause. This minimum blank time shall be configurable. If colours are generated with a colour mixing technology from a cluster of LEDs, failure of any LED within the cluster shall automatically turn off the entire cluster to avoid generation of colour noise. Refer to Appendix A. Single LED failure, provided that the cumulative LED loss remains below the 2% and/or 20% thresholds described above or TVMS light sensor failure, should not result in blanking of the display.

11.3LED output#

Each individual LED shall be driven with a continuous current with no peak and/or magnitudes exceeding 70% of the LED manufacturer's maximum continuous rating.

11.4Character and graphical display formats#

The TVMS sign shall be capable of displaying:

  • a) text
  • b) graphics, or
  • c) a combination of text and graphics.

All signs shall display their colours against a matt Black background.

11.4.1Display Unit (DU) Requirements#

Type A, Type B and Type C VMS shall comply with the display dimensional requirements of AS 4852.2.

Each alphanumeric character in the DU shall be formed by a matrix arrangement of horizontal and vertical pixels.

The signs shall have sufficient vertical pixels to permit lower case text, with descenders that lie wholly below the base of the upper-case characters. The character format shall be complied with the requirements of AS 4852.2.

The type of TVMS proposed for each location shall comply with the requirements of QGTM Part 10 and the Queensland MUTCD Part 3, and shall be specified on the design documentation.

11.5Display fonts#

As a minimum, the variable message display shall generate single stroke alphanumeric character fonts generally to the requirements of AS 1742, AS 1743 and AS 1744. The characters shall be arranged to have a minimum of 2 pixels between characters and 2 pixels between lines.

11.6Display changes#

Variable message display changes shall be in accordance with the TVMS Use and Operations Guidelines. All display changes shall be affected by first blanking the respective DU, and then activating all required pixels of the respective display simultaneously (as apparent to the eye).

11.7Fallback displays#

Facilities shall be included to detect failures within the variable message display(s) and the display control system(s). On detection of a failure, the relevant display(s) shall be blanked to prevent confusing displays to the motorist. Loss of communications with STREAMS shall also be considered a TVMS failure and shall result in the display(s) being blanked after a pre-set time period. This time period shall be a variable, able to be set by STREAMS, with a range of 60 seconds to 600 seconds.

11.8Optical performance#

The performance of the TVMS displays must meet or exceed the optical characteristics defined in Clauses 11.8.1 to 11.8.6. Tests shall be performed by a NATA or NATA-accredited or NATA-endorsed by Mutual Recognition laboratory and the results submitted to the Principal. Witness Point 1

11.8.1Luminance#

The performance of the TVMS displays must meet or exceed the luminance and chromaticity parameters defined in AS 4852.2.

11.8.2Display colour#

The TVMS display shall be either be capable of displaying Monochrome (Yellow) or 5 Colour (Yellow, White, Red, Green and Orange). Yellow, White, Red, Green colours shall be compliant with AS 4852.1.

  1. 1.For monochromatic signs TVMS display shall be able to display individual pixels in Yellow against a matt Black background. LEDs shall be used within pixels to generate the output colour.
  2. 2.The VMS display shall be able to display individual pixels in either Yellow or White or Red or Green or Orange colours, against a matt Black background. LEDs shall be used within pixels to generate output colours. The individual pixels may generate colour with either discrete LED(s) for each of the 5 colours or via a colour mixing arrangement with RGB LEDs or equivalent technologies.
  3. 3.Yellow, White, Red, Green colours shall be compliant with AS 4852.2.
  4. 4.AS 4852.2 does not define the Orange region. The coordinates defined in Table 11.8.2 below are designed to fall within the Orange region for the retroreflective fluorescent Orange in AS 1906, having established that the TVMS Yellow region of AS 4852.2 largely falls within the retroreflective fluorescent Yellow region in AS 1906.
  5. 5.In the event of the use of colour mixing or equivalent technology, any non-compliant colours to AS 4852.1 shall neither be configurable nor displayed under any circumstances.
Table 11.8.2 – Chromaticity coordinates for orange
Colour1234
Orangex0.630.610.640.66
y0.370.370.340.34

11.8.3LED dimming#

The dimming requirements shall be as specified in AS 4852.2.

The LED intensity shall be controlled to provide maximum legibility distances for the complete range of ambient light under which the TVMS shall operate.

11.8.4Luminance intensity half angle#

The luminance half angle for type A, B and C signs shall meet the intensity half angle parameters defined in AS 4852.2.

11.8.5Luminance intensity uniformity#

The luminous intensity uniformity requirements shall be as specified in AS 4852.2.

11.8.6Sun phantom#

The action of sunlight or other bright light sources on the optical elements shall be controlled such that inactive pixels shall not appear active.

Source: MRTS262 · pages 25–27 Open PDF at this page Search this document