About ramp signals

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 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.

^ Back to top

How do ramp signals work?

Ramp signals operate according to traffic flow with electronic sensors, built into the road, detecting when traffic becomes heavy. A message is then sent via fibre optic cables to an automated server which immediately switches the ramp signals on.

The signals manage the flow of traffic onto the motorway during peak periods and other busy times. The signals only operate when needed to improve traffic flows. At other times they remain off.

The system is made up of a number of traffic detectors and associated algorithms that detect when queues are building and changes the signal phasing to speed up traffic through the on-ramp. The system can also be switched off completely when traffic volumes demand it.

Depending on location, additional cameras and detectors are installed on the approach to the on-ramp to measure the ramp and local road traffic volumes. The New Zealand Transport Agency operators have a range of cameras giving a continuous view of traffic operations in the area.

The system is remotely monitored and managed as part of operations at the ATTOMS traffic management centre in Northcote.

View a video of how ramp signals work.

Why do we need them?

Currently traffic on the motorway is disrupted by 'bottlenecking'. This means whenever traffic enters the motorway and then shifts from lane to lane, it creates a slowing pattern as vehicles back up behind the on-ramp entry zone.

Most accidents on Auckland motorways happen during peak hours when traffic is stop-start, due to lapses in driver concentration and motorists travelling down crowded on-ramps vying for positions in traffic or trying to merge together.

Ramp signalling provides a smoother flow of traffic, minimising stop-start conditions by separating on-ramp traffic into streams of one or two vehicles. Ramp signals are designed to keep traffic flowing on the motorway and to reduce accidents.

With traffic on Auckland motorways growing, Transit is taking proactive steps to help reduce congestion by managing its existing motorways in the best way possible. Intelligent management is vital to sustaining and maintaining our motorways.

^ Back to top

Project Objectives

The ramp signalling and ATMS projects aim to:

  • Improve reliability of travel times on the Southern Motorway
  • Improve safety for users (e.g advance information about hazards)
  • Support integrated traffic management (e.g public transport initiatives)
  • Improve the travel efficiency for bus and freight transport (e.g provide priority access to bus/freight transport)
  • Improve information for motorists (e.g electronic message signs for road users)
  • Manage the effects of incidents on traffic (e.g improving warning systems when incidents occur)
  • Enable ongoing monitoring of ramp signalling system and ensure a responsive system (e.g real time monitoring of traffic management)
  • Ensure the system is sustainable in the long term

Working with Others

Ramp signalling is being launched by Transit New Zealand, working together with Auckland's City, Regional and District Councils, Auckland Regional Transport Authority and Land Transport NZ.

Transit has been involved with these councils and agencies through ongoing consultation. It will continue to work alongside these organisations to ensure the smooth implementation of ramp signalling in each of Auckland's major centres.

^ Back to top

Benefits

By introducing ramp signalling to the Auckland motorway network, Transit will deliver the following benefits:

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

Ramp signalling is one of a number of initiatives being introduced by Transit to help deliver these benefits. The combination of these ideas is what is known as Travel Demand Management (TDM). Through its commitment to TDM, Transit aims to increase mobility by improving the efficiency of the motorway network and enabling people to make choices about how, when and where they choose to travel. 

View more on travel demand management here

^ Back to top

Outcomes

There are working examples of ramp signals in Auckland within the Central Motorway Junction, at each of the southbound ramps along the Southern Motorway between Hobson Street and East Tamaki, and at the Takanini and Papakura interchanges. Ramp signals are also being installed at the northbound on-ramps starting at Gillies Avenue and Mt Wellington.

Ramp signals at these locations followed on from an earlier trial at the SH20 Rimu Road on-ramp, Mangere Bridge in 2003. The 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.

Results

While there is no single simple answer to Auckland's traffic pressures, these results show that the system is helping to make much improved and more efficient use of the overall transport network.

Data gathered since the signals have been turned on has given the following results for individual sections of the Southern Motorway (SH1):

Curran Street northbound

  • Improved northbound traffic flows on clip-on lanes on Auckland Harbour Bridge
  • 18% - increase in throughput of vehicles
  • 12% - improved peak period travel speeds

Wellington Street northbound and Northwest - North/Port-North

  • 6% - increase in throughput of vehicles
  • 4.5% - increase in travel speeds

Hobson Street to Market Road southbound

  • 15% increase in throughput of vehicles
  • 16% improved travel speeds
  • Commuter traffic cleared 20-30 mins earlier during afternoon peak periods
  • Safer merging and motorway incidents being cleared up to 15 minutes faster, to restore normal traffic flows

Between central city and Ellerslie-Panmure, Mt Wellington and East Tamaki Interchanges southbound

  • Peak period traffic flows have been significantly improved
  • Shortened periods of congestion
  • Motorway is carrying significantly more traffic during peak periods than before
  • Travel speeds have increased

Ramp signalling has been used for many years overseas as an integral part of comprehensive motorway management systems. The following statistics (averages) have been shown in similar projects in the United States and Europe, and are consistent with the expected outcomes in Auckland:

  • 9% - Increase in throughput of vehicles
  • 14% - Overall speed increase
  • 22% - Decrease in travel time
  • 24% - Reduction in crashes
  • 91% - Improvement in the reliability of journey times

More information about these outcomes in overseas studies can be found on the following websites:

 

^ Back to top

Priority Lanes

The New Zealand Transport Agency is aiming to improve journey times and create a more free-flowing motorway with the opening of priority lanes at on-ramps.

Truck priority lanes allow trucks to bypass the ramp signal without stopping and losing momentum, especially when on-ramps are on an incline. The faster access also means that trucks can maintain a good speed onto the motorway, and will not slow down other vehicles. The first trucks-only priority lane opened in October 2007, from the Grafton Road southbound on-ramp to the Southern Motorway.

The truck, bus and car-pool priority lane gives car-pool vehicles (two or more people per car), trucks and buses faster access to the motorway. The benefit of the lane is to move more people rather than more cars to the benefit of commuters who car-pool or use buses. The priority lanes will also make a big difference to the freight industry giving truck operators more reliable travel times on the motorway.

The priority lane for trucks, buses and car-pool vehicles will be operating soon at the Mt Wellington and South Eastern Highway northbound on-ramps. Motorcycles can also use the priority lanes, except at Grafton Road southbound on-ramp.

A total of 14 selected on-ramps across the Southern (SH1), Northern (SH1) and Northwestern (SH16) motorways will feature priority lanes for trucks, buses, with car-pool vehicles being added at a later stage.

Priority lanes are also an outcome of the objectives detailed in the New Zealand Transport Strategy's Assisting Economic Development section, by contributing to improving the flow of people, goods and services within and between cities in New Zealand.

View how truck priority lanes work.

^ Back to top

Auckland Ramp Signals

The New Zealand Transport Agency is installing ramp signals on all 31 on-ramps across Auckland's Southern Motorway and Central Motorway Junction (CMJ). Ramp signalling will be progressively extended across the motorway network on the Northern (SH1), Northwestern (SH16) and Southwestern (SH20) motorways.

The first phase of ramp signals has been introduced on the Southern Motorway.

View established sites here

Advanced Traffic Management System (ATMS)

Ramp signalling was launched at the same time as an extension to a system called the Advanced Traffic Management System (ATMS). ATMS is made up of new gantries and advisory signs, which have been added to the Central Motorway Junction (CMJ). These electronic signs (like those on Auckland Harbour Bridge) show recommended speed limits, arrows directing traffic into other lanes and crosses indicating lane closures. Special cameras and electronic sensors in the road have been installed as part of this new traffic management system.

ATMS, along with ramp signalling, helps to manage congestion and improve safety on the motorway network.