What MVMS Are Used For
NZTA's specification lists MVMS as suited to a defined set of situations, in both urban and rural environments:
- Incident management, such as crashes or unusually severe congestion.
- Special events, including road closures or diversions.
- Sites affected by extreme weather or environmental events.
- Route advisory information, guiding motorists to alternative routes.
- Travel time information, where delays are known in advance.
- Safety advisory notices sanctioned as part of an approved campaign.
Site Selection
Unless operational requirements necessitate variations, an MVMS must be positioned to the left of approaching traffic. Positioning it on the right-hand side is considered unsafe, since it may confuse a motorist's point of reference at night and increase head-on collision risk.
The sign should also be positioned to avoid obstructing drainage or the flow of water, and installed on a straight road alignment so drivers have a clear sightline and enough time to view and react to the message.
Clear Sight Distance
For a 100 km/h speed environment, choose sites offering clear sight distance to the sign of at least 300 metres, reduced proportionally in lower-speed environments. Make sure other signage, structures, or vegetation do not obscure the sign.
Avoiding Sunlight Glare
Where possible, avoid positioning the sign directly in front of a rising or setting sun, since this can significantly reduce visibility, and sun reflections on the display face can reduce legibility even with a hood or louvres fitted. Where a natural backdrop such as a hill, trees, or a downhill slope cannot mitigate this, a hood or louvres must be used to shield the display.
Road Geometry
Avoid positioning an MVMS immediately before a sharp bend, blind crest, or intersection, where it could distract attention at a critical moment. It must also not be positioned where its display could be seen from a neighbouring road if this would give motorists confusing or conflicting information.
Route Diversion Messaging
If an MVMS is intended to advise route diversions, it should be located far enough in advance of the alternate route intersection to give motorists time to read the message and respond, including changing lanes if necessary. NZTA's specification leaves the exact distance to professional judgement based on the specific site, rather than setting a single fixed figure.
Avoiding a Hazard or Hindrance
On motorways, an MVMS will normally need to be positioned behind barrier protection. In high-volume urban and rural contexts, for speed environments at or above 70 km/h, an MVMS should be sited outside the clear zone or behind barrier protection. For speeds below 70 km/h, it should be located as far from the road edge as practicable.
Visibility, illumination, and safety under night-time or adverse weather conditions all need consideration, and placement must never impede pedestrian footpaths or cycle lanes.
Build and Durability Requirements
NZTA's specification sets minimum technical requirements for the sign and trailer itself, not just where it is placed:
Ingress Protection
Enclosures must meet a minimum IP56 rating against water and dust.
Wind Rating
Designed to withstand wind gusts of up to 180 km/h in operation mode.
Battery Runtime
At least 48 hours of operation without recharging, with a minimum 24-month battery design life.
Design Life
A specified 10-year design life for the overall asset.
In operation mode, the lower edge of the display panel enclosure must sit between 2.1m and 2.5m above local ground level, with the rear of the trailer and the display facing approaching traffic. Trailers carry a 5-year warranty, with the sign component covered separately for 2 years.
Deployment
When deploying an MVMS, operators should ensure:
- The rear of the trailer faces oncoming traffic.
- The handbrake is on.
- The wheel clamps are fitted and locked.
- The stabiliser legs are extended firmly to the ground.
- The battery is fitted and securely locked.
Deployment in Wind
The sail area of the raised display can exert significant overturning forces on the trailer in moderate to high winds. In addition to the standard deployment checks, operators should use the lash-down straps provided to anchor the trailer, with the most important points being those on the windward side. Only raise the display to the lowest operational configuration if needed, noting a fully raised display gives better visibility in moderate to high traffic volumes. If very high winds are expected, place the display in transportation mode or move the MVMS to a position of safety until winds abate.
Messages
Messages posted on an MVMS should comply with the standard message design processes outlined in NZTA's Variable Message Signs Operating Policy and Procedures, using the standard messages provided in that documentation where possible.
Inconsistent or contradictory messages can arise between an MVMS and fixed VMS. To ensure road users receive consistent information, the appropriate Transport Operations Centre should be made aware of any proposed MVMS message before it is displayed.
