Transit introduces easy merge signals
Auckland Regional Office
25 February 2004
Transit introduces easy merge signals to reduce motorway congestion
In an initiative to reduce queuing on the Southwestern Motorway (SH20), Transit New Zealand is trialling a system to ease traffic merging onto the motorway from the Rimu Road-Mahunga Drive on-ramp. The system will operate during peak times from Monday 1 March.
The Rimu Road-Mahunga Drive on-ramp, just south of the Mangere Bridge, carries upwards of 65,000 vehicles a day. Closely spaced vehicles merging from the on-ramp at peak times slow motorway speeds from 80km/h to around 25km/h. This causes traffic to back up several kilometres south of Mangere Bridge.
Transit will trial its ‘easy merge’ traffic signals on the ramp to smooth the flow through the merge area and reduce congestion.
During heavy traffic flows, sensors measuring traffic on the motorway will switch the signals on automatically. The lights will change very quickly, allowing two cars at a time on each green signal to merge with the motorway traffic.
When the lights are red, motorists will stop at the white line and wait for the green signal. When the lights switch to green, the first vehicle in each queue may go and merge with the motorway traffic. The following vehicle will wait for the next green signal. Electronic signs before the on-ramp will advise drivers when the ramp signals are operating. When the signals are not operating, on-ramp traffic may proceed and merge with motorway traffic as usual.
Transit regional manager, Wayne McDonald, says that pulsing vehicles onto the motorway prevents the tight groups of vehicles that are generated at uncontrolled on-ramps. “This allows traffic to merge without the breakdown that is a feature at many on-ramps on the motorway network,” he says.
Mr McDonald says that while the system may at times lead to increased queues on the ramp, international experience – as well as short trials conducted in New Zealand – have shown improved overall traffic flow.
“This easy merge initiative is the latest step in addressing the Auckland region’s chronic congestion problem, which is costing upwards of $1 billion a year in lost time, access difficulties, fuel and stress,” he says.
“Easy merge is a smart, cost-effective, technology-driven solution that fits in smoothly with the rest of the traffic management measures that are being employed increasingly throughout the motorway network to keep traffic moving smoothly and safely.”
Mr McDonald says that based on the success of the present easy merge trial, similar on-ramp controls will be introduced at other sites on the motorway to reduce congestion.