Rumble strips failed to slow down motorists on a rural Canterbury intersection, according to a recent council trial.
Ashburton District District trialed the rumble strips to warn drivers of the intersection ahead.
Data from the trial showed the strips didn’t slow drivers down, and some motorists appeared to drive straight through the stop sign.
The intersection now has larger gated stop signs and stop ahead warning signs.
Infrastructure and open Spaces group manager Neil McCann said the data was recently presented to the Ashburton District road safety co-ordinating committee.
“The data showed similar speeds were recorded pre and post-rumble strip, so we can’t conclusively say the rumble strip had any impact,” McCann said.
The rumble strip was installed on the west approach of Fairfield Road to Singletree Road, 200m from the intersection and had five 15 mm high strips 300 mm apart.
A traffic speed count was carried out at 20 metres from the intersection before the installation of the strips and then after the installation, to see if they made drivers more aware of slowing down for the intersection.
In his report on the three stage trial that took place between March and September, roading manager Mark Chamberlain said the speed data showed “no significant difference of the speeds approaching the intersection, before and after both the rumble strip installation and the change in signage”.
“Speed readings had similar numbers pre and post-rumble strip installation,” Chamberlain said in his report.
“They are not different enough to conclusively say there was any impact from the rumble strip install.”
It was a “simple trial” at a single rural intersection which has relatively low traffic volumes.
McCann said the rumble strip data showed about 98% of vehicles were travelling less than 40kph as they slowed for the intersection, before and after the installation of the rumble strip.
“But some were travelling a lot faster, and it looks like several vehicles must have simply driven straight through without realising it was a stop sign.”
The council will continue to look at ways to improve road safety at rural intersections, while continuing to upgrade its signage, McCann said.
That work includes changing give way signs to stop signs, using larger signs, gating signs, and installing advance warning signs to alert drivers that an intersection is ahead he said.
A focus on improving safety at rural intersections followed a 2022 coroner’s report into a triple-fatality at the intersection of Mitcham and Hepburns roads near Ashburton in April 2019.
The report recommended the council review 79 rural intersections, which resulted in 33 of the list being identified for improvements which were completed in 2023.
By Jonathan Leask
