Ramp signalling is an internationally proven traffic management tool used with great success, in the United States, Great Britain, Europe and Australian cities such as Melbourne and Sydney.

By managing the rate at which vehicles enter the motorway, ramp signalling results in:

• More consistent and predictable travel times
• Safer merging
• Fewer accidents
• Better throughput of vehicles on the motorway
• More consistent speeds

Transit is installing ramp signals on on-ramps across the motorway network, with 16 ramps on the Southern Motorway and in the Central Motorway Junction.

The first ramp signals began operating in December 2006. Ramp signals are expected to be operating across the Southern, Northern and Northwestern motorways by the middle of 2009.

Ramp signals are also being used to manage traffic flow on major new motorway-to-motorway links, for example the new Northwest and Port to North links.

The first trial ramp signals were installed in 2003 on the Southwestern Motorway (SH20) at the Rimu Road on-ramp, Mangere Bridge. These signals first tested the technology and measured the benefits that ramp signalling has, on Auckland motorways. The Rimu Road ramp signals operated in isolation, without the benefit of a full motorway ramp signalling system. Nevertheless, they delivered noticeable improvements to throughput and safety on the northbound motorway lanes.

What are ramp signals?

Ramp signals are traffic lights at the top of motorway on-ramps that manage the flow of traffic onto the motorway during peak periods. With each green light, two cars (one from each lane) are able to drive down the ramp to merge easily, one at a time, with motorway traffic. Vehicles move forward every few seconds between green lights. Separating the vehicles travelling down the on-ramp makes merging onto the motorway easier and causes less disruption to motorway traffic flow.

View a video of how ramp signals work.

How Ramp Signals Work

When lights are red:

Stop and wait for green signal.

When lights are green:

One vehicle in each lane goes. The next vehicle in each lane moves forward and waits for their turn. Ramp signals run on a quick cycle, only a few seconds between green lights.