Don’t you hate it when you see a green light coming up that starts to turn orange just as you approach? What if there were intelligent traffic lights that communicated with your vehicle via 4G to make traffic flow more efficiently through a busy road network? That’s what we’ve tested as part of a new technology trial in South Australia.

It’s called V2I, or Vehicle-to-Infrastructure communications. At several real-world intersections in South Australia, we’ve enabled vehicles connected to our 4G network to support new V2I applications designed to make traffic flow smoothly.

Selected traffic light test locations in South Australia

Using virtual roadside units for V2I

We’ve worked with Cohda Wireless, JYW Consulting and the South Australian Government’s Future Mobility Lab Fund, which aims to encourage and stimulate developments in connected and autonomous vehicles, and position South Australia at the forefront of these emerging technologies.

Instead of having to deploy short-range radio hardware at every single traffic light intersection, we instead made use of our existing leading 4G network to keep implementation costs low and enable faster deployment of V2I applications across the road network.

Traffic lights today are typically connected to a central traffic light management platform but use a local controller built on timers and local in-ground sensors to help manage the flow of traffic through an intersection. What this new trial achieves is the ability of an approaching vehicle to receive and send messages via our 4G network directly into any set of traffic lights connected to the traffic light management platform.

We achieved this by developing virtual roadside units (Virtual-RSUs) in software that interact with the vehicle and the traffic light management platform. Just like hardware roadside units, the Virtual-RSUs broadcast intersection geometry information messages and traffic light signal phase and timing messages, but do this via 4G instead of short-range radio. The Virtual-RSUs accesses traffic light information via a new component developed in the trial called the SCATS SPaT Engine (SSE), which generates signal phase and timing messages based on live information from the centralised traffic light management platform.

What we can do with V2I

Using 4G and cloud platforms, traffic light timing and intersection mapping information, can be sent to V2I connected vehicles based on their position – without the need for new hardware on the traffic lights themselves. With this new capability, our consortium trialled four new V2I applications in Adelaide, South Australia at several selected intersections.

Freight signal priority (green light extension)

Using connected test vehicles, we tested an application called freight signal priority which allows heavy freight vehicles to request the extension of an active green light, to allow them to get through the intersection without stopping. The goal is a reduction in the number of times a heavy vehicle needs to stop at traffic lights with the aim of improving traffic flow at the intersection and reducing fuel use and trip time for heavy vehicles.

Similarly, public transit vehicles would also be granted priority through these smart intersections. If priority is granted, a green light extension will be issued by the central traffic light management centre to the local traffic light. During the trial we also tested that when the vehicle stops in a prescribed bus stop, any pending or granted priority requests for traffic lights up ahead are cancelled.

Trial vehicle executing tests

The technology can also allow emergency vehicles to travel through intersections more smoothly. It allows emergency service responders to extend a green light, or even override the traffic lights and force them to green on their approach.

Finally, we tested an application that can help connected passenger vehicles get a smoother “run” of green lights to improve their flow and reduce congestion in busy areas. While making no changes to the intersection traffic light timings, the system instead provides advisory information to connected vehicles, in the form of a suggested optimal speed to enable them to catch the green light at the next intersection. On approach to an intersection, vehicles are sent the timing of the traffic lights over the 4G network allowing the vehicle to modify its speed so that it optimally arrives at the intersection as the light in the direction of travel is green.

These V2I applications are part of a greater Co-operative Intelligent Transport System (C-ITS) approach, which also includes Vehicle-to-Vehicle (V2V) communication and Vehicle-to-Pedestrian (V2P) for safety applications. The 4G link used in the trial is also useful for other Network-to-Vehicle (N2V) communications – for instance, to communicate a bad road surface, weather or other information to distant vehicles and so that they might choose to re-route and avoid the area.

This suite of Vehicle-to-Everything (V2X) technologies – including a recent trial we completed with Lexus – is preparing the Australian road network for our eventual self-driving future. But between now and then, we’re working hard to ensure that the benefits of smart infrastructure help all road users have a smoother journey.

Abbreviations key

C-ITS – Cooperative Intelligent Transport System

N2V – Network to Vehicle

RSU – Road Side Unit

SCATS – Sydney Coordinated Adaptive Traffic System

SPaT – Signal Phase and Timing


V2I – Vehicle to Infrastructure

V2P – Vehicle to Pedestrian

V2V – Vehicle to Vehicle

V2X – Vehicle to Everything