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Visual clutter proved a road safety hazard

1 April 2009

Cars on road

New Monash research proves prominent advertising, signs or billboards on our roadsides can be a distraction for drivers - especially older ones.

The Monash University Accident Research Centre (MUARC) research has important implications for the design and regulation of road environments, including advertising along our roads and highways.

It found the advertising delays drivers' ability to detect changes around them - such as a vehicle changing lanes - by an average of half a second. Older drivers took the longest to react.

"Driving on a typical major road is a complex activity, where drivers must process large amounts of visual information which continuously changes, and make decisions at speed," researcher Jessica Edquist said.

"As drivers we can only look at and pay attention to one thing at a time. When we are looking at a sign or a billboard, we are not looking at the road, leading to a higher accident risk."

Ms Edquist conducted a series of tests with more than 100 drivers, almost half using MUARC's driving simulator. She found drivers were distracted by billboards and drove more slowly, took longer and made more errors when changing lanes.

Older drivers in particular had difficulty detecting changes on the road and in following road signs in busy environments.

Ms Edquist said road authorities should carefully regulate billboards, declaring billboard-free distances around areas of high driver workload such as intersections, merges and freeway exits.

"Road authorities should also give advance warning of hazardous situations with ‘priming' road signs to spread the cognitive workload. These adjustments are especially important for busy roads with many other vehicles, cyclists or pedestrians," she said.

Her work has already led to changes in Queensland and will bolster arguments made by road authorities that roadside advertising should sometimes be restricted on safety grounds.