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Updating the sound of safety

If you’ve ever driven over rumble strips, you’ll know how well they engage the senses. The rhythmic drumming and vibrations are unmissable. Just as well. Technically known as Audio Tactile Profiled Marking (ATPMs), the little plastic ribs alert motorists when they drift from their lane.

You may not have given ATPMs much thought - until now. Guidance for how they’re used has been updated by the NZ Transport Agency (NZTA) for the first time since 2010. Parts of the new guidance feature research from WSP’s road safety and human factors experts.  

WSP Petone-based research leader for road safety Bill Frith says ATPMs have been an important feature of New Zealand roads since the 1990s. International studies dating back to 2007 show they have a well attested safety benefit. Latest research from the US, for example, shows they can reduce death and serious injury crashes by up to 22 percent on rural two-lane two-way roads.  

"Audio tactile profile markers are a huge win for everyone on the road, helping ensure safer journeys for all,” he says.   

A 2012 WSP study features in NZTA’s new guidance, highlighting that wider ATPM ribs can improve road safety by increasing visibility. As a result of that work, the guidance recommends a new minimum 150mm width for ATPM ribs.  

One of the recommendations in the new guidance follows a WSP field trial from 2017. ATPM ribs can now be placed 500mm apart on the edge of a road. The previous recommended distance was 250mm, but WSP’s field trial showed no appreciable difference in how noticeable they are to drivers at the wider spacing. 

“There’s been several major studies on ATPs done in New Zealand and overseas since the guidance was first issued. It’s fantastic to see NZTA’s guidance now evolve with the latest evidence, reinforcing the life-saving potential of these small but impactful devices,” says Bill.