New measure to benefit all commuters coming into Christchurch from the north


Early morning motorists travelling southbound on Christchurch’s Northern Motorway at reduced speeds are having 35 to 45 seconds added to their journey time from south of Ohoka Road to Dickey’s Road for the benefit of all commuters, says the NZ Transport Agency.

From this week, the variable speed signs have been turned on at 5.50am. This limits motorists’ speed on the Northern Motorway to 70km/h and helps to reduce the impact of their braking as they enter Belfast on the thousands of other motorists that travel during the morning peak, says the Transport Agency's Southern Regional Director Jim Harland.

“This new measure is about getting as many people to their destination as efficiently as possible during the busiest times and for everyone to enjoy more predictable journey times. By limiting speeds earlier in the morning we can keep more people moving through the network with reduced delays.

“Even if the motorway is clear of traffic, the 70km/h speed limit will operate along this three-kilometre section of motorway to help delay the onset of breakdown in traffic flows and reduce the number of people experiencing significant delays.

“During the busiest times, motorists will still experience slow journey times.”

The Transport Agency introduced variable speed limits on the Northern Motorway two weeks ago to help reduce delays and driver frustration during the morning’s peak travel to help delay the breakdown in flows when vehicles brake as they enter Belfast causing a "slowing" ripple effect through the traffic. The people braking do not see the impact behind them on the motorway.

He says by introducing the 70km/h speed limits just south of Ohoka Road at 5.50am, the 35 to 45 second delay for motorists at this time will save other motorists at least five minutes travel time. “The travel time savings may seem small but from this we hope to make even more gains, and more importantly, start to establish more predictable journey times for motorists.”

Mr Harland says after the first week’s operation, which resulted in minimal impact because of an overall 12% increase in traffic volumes compared to the previous week and some technical issues, work has been done to tweak the operational times and some positive results were starting to emerge. “We still have a way to go and are again asking motorists for their patience as we fine tune the new operational time for the variable speed limits.  

"We are again asking motorists to help by observing the speed limits which are legal and enforceable, keep a constant speed and avoid speeding up/slowing down, and minimise lane changing.  

“Motorists on the motorway and those entering from the side roads have to think about the overall impact of their actions on traffic flows and the morning commute time. “While we encourage courteous driving behaviour, during this morning peak letting vehicles in from side roads is adding to the congestion and travel delays.” 

He says everyone using the motorway during the morning peak has a role to play ensuring they observe these behaviours to help everyone start to benefit from a more predictable journey time.

“Motorists need to think of the variable speed limits as helping to manage the number of vehicles attempting to get through a single point on the motorway at one time. It's like pouring water through a funnel, if you pour it quickly the funnel fills up and it takes time to drain away. If you pour the water in slowly, it will flow through the funnel without pooling in it. That is exactly how the variable speed limits are designed to work.”