8.3.1 Types of Electronic Roadside Signs
There are two main types of permanent electronic roadside signs deployed to support smart motorway operation; mainline VMS and arterial road VMS, as outlined below:
- Mainline variable message signs (VMS) are multi-purpose, full matrix signs that can display a variety of message types, including text and pictograms. VMS are installed on the motorway mainline in advance of key decision points (i.e. major exits/interchanges).
- Arterial road VMS may be installed to provide advance motorway condition information, to enable improved route choice prior to entering the motorway. This is particularly important when the motorway is congested or affected by an incident, and there are alternative arterial routes with a shorter overall travel time to the same destination.
Permanent VMS may be used to address localised performance issues on a motorway or to deliver messages to individual at-risk vehicles. For example, weather warning systems, heavy vehicle speed warning on curved entry ramps and over-height vehicle warning on approach to tunnels and other low clearance structures. Portable/temporary VMS are used for incident, road works and special-event management.
Historically, purpose-built, dedicated travel time signs have also been used on motorways and arterial roads. These signs comprise a standard retroreflective static sign with embedded electronic components that are used to display motorway travel times and/or colour-coded motorway condition information, such as illustrated in Figure 8.3. These signs have been referred to as motorway condition information signs, trip information signs, drive time signs and trip condition signs.
Source: Austroads (2016b).