Vehicle mounted Variable Message Signs (VMS)

Vehicle mounted Variable Message Signs (VMS) are sometimes required to be used to comply with slow downs over major road infrastructure as stipulated in a NHVR Oversize Overmass Vehicle Permit.

When required as a permit condition the: 
  • VMS must be either towed or fixed to a vehicle 
  • VMS must display all messages in an amber colour 
  • VMS must be capable of operating at speeds up to 100km/h 
  • layout of any VMS must comply with all relevant requirements of Victoria's Road Safety Road Rules 2009, Australian Standard (AS) 1743-2001 Road Signs - Specifications and AS 1742 Manual Of Uniform Traffic Control Devices 
  • character heights and border widths for text type signs must comply with the guidelines detailed in the table below 
  • display characters must comply with the appropriate font, as defined in AS 1744-1975 Standard Alphabets For Road Signs. 

NOTE : It is accepted that due to the ‘flaring’ of illuminated displays, the widths of the characters may be slightly less than that required for a static sign. Each character shall be either single stroke width (single row of LED’s) or double stroke width (two rows of LED’s) and the display of a VMS shall be surrounded by a matt black border, as detailed in the table below.

Recommended character heights, stroke widths and minimum border widths

Speed limit  Recommended character height  Recommended stroke width Minimum border width
40 km/h  80 mm single 75 mm
60 km/h  120 to 150 mm single 100 mm
80 km/h  200 to 250 mm single

150 mm

 100 km/h  350 to 450 mm  single or double  200 mm
 110 km/h  450 mm  single or double  250 mm

Frequently asked questions about when a VMS is required and how the VMS should be used

What is the criteria that NHVR Statewide Permit Group use to trigger the additional permit condition that a VMS is required to follow a load?

Any oversize (usually overmass) load that is required to reduce vehcile speed to 5 to 10km/h to cross a structure on a high speed road (100km/h or greater) will require a NHVR escort and a VMS sign to warn traffic of the slow moving vehicle ahead.

What roads, highways, freeways is this condition (requiring use of the VMS) applied to? 

Any road where the speed limit is 100km/h or greater.

What operating criteria are transport companies/pilots required to follow when using a VMS?

Transport companies/pilots are required to follow the directions of the NHVR Safety and Compliance Officers (SCOs) who will be escorting the load or supervising the bridge crossing. There may be different instructions for different sections of road and traffic conditions, e.g. placement of the VMS in relation to the load. 

What is the standard wording to be displayed on the VMS? 

The standard wording to be displayed on the VMS is generally "Caution slow moving load ahead".

However the wording may vary depending on the section of road, the load or traffic conditions. Generally it is expected that the wording on the VMS can be easily programmed. 

Who is authorised to tow or carry a VMS? Will a driver’s license suffice or is the driver required to be a certified pilot or an accredited traffic controller?

To tow or carry a VMS only a drivers licence is required, however the driver of the vehicle towing or carrying the VMS must not be one of the pilots required in the permit conditions to move the load, e.g. if the load requires two certified pilots and a VMS vehicle there must be two certified pilot vehicles plus an additional vehicle towing/carrying the sign.


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