Wellington’s smart motorway opens at the beginning of June ending a sustained period of construction on the busiest stretch of highway in the region. NZ Transport Agency’s Wellington highway manager Neil Walker says the central median barrier replacement dictated the length of time to complete the project.
“The smart motorway has been a project in two parts; the physical works, of which the largest task was constructing a new northbound lane, and the technology side which was about building and commissioning the smart motorway system,” says Walker.
The smart motorway concept was introduced first in England in 1995 on the London Orbital motorway, the M25.
“Smart motorways work by smoothing the traffic flow. Slowing the traffic reduces the gap between vehicles meaning more can fit on the road at any one time. Without the stop-start driving pattern which is a feature of congested traffic, vehicles keep moving and get through sooner with less stress,” says Walker.
“Theory tells us that around twice the number of vehicles can get through a section of road when they’re travelling smoothly at 70-80kph, compared to when they go at 100kph. But as more vehicles travel on the road and the distance between vehicles reduces, the chance of traffic flow being disrupted increases,” he says.
“The smart motorway assists drivers by informing them of the correct speed for the current conditions. Drivers can help by following the directions of the electronic signs, minimising lane changes and merging like a zip when needed, ” says Walker.
The smarts of the system come from a network of equipment that measures what’s happening on the road, processes this data to determine the optimum speed, and then displays the results in real-time to drivers.
The most critical time when the system can influence congestion is when the volume of traffic is beginning to build up, that is before the road becomes congested. It’s at this pre-peak time that the system will begin to slow traffic entering the area so vehicles can continue to flow smoothly through the area.
Because the road shoulder between the Aotea Quay on-ramp and Ngauranga has been removed to make way for the fourth northbound lane, two emergency stopping areas have been built.
Drivers can pull in here if their vehicle gets into trouble, which will also reduce the impact of an incident on the rest of the traffic. Installed in each emergency stopping areas is an event detection camera and a phone which connects straight through to the Wellington Transport Operations Centre (TOC).
Drivers can talk to the operators via the direct line or use their phone to arrange the help they need. They can then wait safely in the emergency stopping area until help arrives.
If required, TOC operators can display the Red X to close a lane and allow support vehicles to get there as quickly as possible. Motorway rules apply to the emergency stopping areas; drivers can only stop there in a genuine emergency (which doesn’t include taking a phone call).
When a vehicle is ready to leave the emergency stopping area, TOC operators can display the Red X on the variable message signs to close the lane behind the area. This feature empties the road, so drivers have time to get their vehicle up to the same speed of the rest of the traffic.
“Having a tow truck on standby during peak times will become a permanent feature of the smart motorway following a successful trial during the project. Peak-time crashes are low impact regarding injuries, but high-impact regarding their effect on other road users,” says Walker.
“Results from the trial demonstrated a decrease in response time and associated congestion, so we’ve decided to make the stand-by response vehicle a permanent feature during peak travel times on the smart motorway,” he says.
A southbound on-ramp for emergency services is another feature included in the project. Currently, Ngauranga-based Road Police Officers heading to the city or northern suburbs have to drive up the gorge, turn around at Newlands and head back down State Highway 1.
