With works on the $80 million Sumners Road interchange upgrade winding up, access to the centenary motorway in Brisbane’s south-west will significantly improve. Roads & infrastructure discovers what the project has involved.
Sumners Road interchange provides access to the Centenary Motorway from the highly populated western Brisbane suburbs of Jamboree Heights, Sumner, Sinnamon Park and Darra.
Before the $80 million upgrade, which began midway through 2019, the interchange comprised a two-lane bridge over the motorway connected by two roundabouts.
Queueing on the 100 kilometer per hour motorway and traffic delays on Sumners Road were a regular occurrence as more than 35,000 vehicles, including about 1750 heavy vehicles, used the interchange daily.
Significant peak-hour congestion also deterred commuters from accessing the nearby Darra train station, while active transport options were limited. Queensland’s Transport and Main Roads Minister, Mark Bailey, said an upgrade was certainly needed to provide greater time savings and better outcomes for all road users.
“This project has replaced the two roundabouts with signalised intersections, demolished the old two-lane bridge and built two new bridges, providing six traffic lanes in total,” Bailey said.
“A key highlight is the much-improved active transport facilities which connect with the Centenary Bikeway.”
Construction has involved demolishing the four-span bridge, built in 1965, and replacing it with two new ones.
The new, two-lane, eastbound bridge was built before the existing bridge was demolished. The new, four-lane, westbound bridge, with a shared path for active transport users, followed.
The bridge length crossing over the Centenary Motorway is 55 metres, and the works involved lifting and placing 36 girders (27.5 metres each in length) near live traffic, underneath pylons and high- voltage overhead electrical powerlines.
The existing roundabouts at each end of the bridge were collapsed and replaced with signalised intersections. Additional lanes were added to the on and off- ramps, as well as the local approaches, to accommodate the high volume of traffic.
The eastbound girder lift took more than one week, with 12 girders lifted and placed using a 500-tonne crane and a franna crane.
The westbound bridge had 24 girders lifted and placed using the 500-tonne crane and a 275-tonne crane. Both cranes were positioned either side of the Centenary Motorway to lift and place the girders as a dual lift, with the westbound girder lift taking place over 10 days.
A new, grade separated, bike track was also built as an underpass directly under the western intersection to provide connectivity between the missing link of the existing Centenary Bikeway.
The existing arrangement had limited pedestrian and bike-rider facilities as the off-road Centenary Bikeway terminated at the southern end of interchange and went “on road” for 500 metres before going off road again at the northern end.
“The Centenary Bikeway’s missing link that originally required a 500-metre detour is now solved by the construction of the new underpass,” Bailey said.
The upgraded interchange also improves safety and connectivity for active transport users by providing dedicated, on-road bike paths, a new shared path to existing businesses and new footpaths throughout.
Set in a largely modified urban environment, site inspections took place on a regular basis to ensure all remnant vegetation communities and animal breeding places were identified and monitored.
New trees and plants were planted on the site to replace any vegetation lost, while the project also includes two noise fences totalling 200 metres along property boundaries.
Construction began in July 2019 and progressed ahead of schedule, with completion expected this month (March 2021). But Bailey said delivery wasn’t simple.
“The project has been challenging due to the confined project footprint near houses and businesses, the substantial amount of public utilities, and working over the highly trafficked Centenary Motorway,” he said.
“The staging of construction of the new, two-lane, eastbound bridge, then demolishing the existing bridge and building the new, four-lane, westbound bridge required detailed traffic staging to ensure flow was maintained throughout the interchange.
“The major utility constraint was the high-voltage overhead powerlines, which could not be de-energised, and pylons. Despite these challenges, the project has still run ahead of schedule.”
Bailey said construction challenges presented opportunities for innovation to ensure a quality product was delivered.
The girder lifts for both bridges required strategically placed and weighted cranes on the motorway to safely place the girders. The new, grade separated bike track was built using box culverts.
“The traffic management arrangement was complex to ensure safety and required innovated thinking to reconfigure the western intersection to ensure traffic flow was maintained,” Bailey said.
“The new bridges have also been ‘future-proofed’ to add more lanes on the motorway, as the likelihood that the interchange traffic volumes will increase.”
As a Queensland Ambulance Service (QAS) station is located within the project’s footprint, the interchange has also been sequenced so the new signalised intersection would give QAS vehicles priority emergency access.
With construction now coming to an end and the final configuration in place, Bailey said the Sumners Road Interchange Upgrade would provide great relief to motorists travelling through western Brisbane.
“It will improve safety, travel times for freight and commuters alike, and provide safer active transport facilities with shared pathways and on-road cycle lanes,” he said.
“People will be able to spend less time on the roads, and more time doing what they enjoy.”