What is ramp metering?

If you drive along the Southern Expressway regularly, you might’ve noticed traffic lights installed on the entry ramp at the new Majors Road interchange.
These traffic lights have been installed at the northbound on-ramp at Majors Road to assist with the ramp metering system. It’s the first time the system has been used in South Australia, so here’s what you need to know.
What is ramp metering?
Ramp metering, also known as ramp signalling, is used to control the rate of traffic entering a freeway or, in this case, the Southern Expressway.
The set of traffic lights stops traffic before gradually releasing them on to the motorway. While the Southern Expressway will be the first location where ramp metering takes place in South Australia, the system has been used both interstate and overseas for many years.
How does ramp metering work?
Ramp metering uses sensors on the expressway to detect heavy traffic and trigger the signals.
Vehicles are stopped and then allowed to enter in a controlled manner, with one vehicle per lane entering each time a green light is displayed. This ensures smoother and safer merging and increases the overall efficiency of the freeway.
What you’ll see when entering the Southern Expressway
When entering the Southern Expressway along the northbound on-ramp from Majors Road, you’ll see a set of traffic lights and a couple of signs you may not have come across before, including the ‘stop here on red signal’ and ‘one vehicle per green’ signs in each lane.
When approaching the ramp meter, you treat it like any other traffic signal, obeying the red and green lights. Stop at the red light and proceed at a green light when it’s safe to do so.