The first of three rope bridges and three "glider poles" has been installed across Victoria's busy Hume freeway to allow a means for squirrel gliders, possums and other native animals to pass safely across the road.

The rope bridge and glider poles for animals, the first of their kind in Victoria, is the culmination of a three-year research program into the effect that roads and traffic have on wildlife.

To date, researchers from the Australian Research Centre for Urban Ecology (ARCUE) based at the Royal Botanic Gardens, Monash University, the University of Melbourne and VicRoads have concentrated on finding out how, where and why animals cross the busy freeway.

Dr Rodney van der Ree, an Ecologist at ARCUE and Honorary Fellow at the School of Botany, University of Melbourne, said: "The world's ecologists are watching this program closely because we have a good understanding about what has happened before an animal-only overpass has been built," he said.

"This research will tell us the extent to which purpose built structures help Australia's unique wildlife cross roads more safely."

The bridge and glider poles are mainly being installed for the Squirrel Glider, a species threatened with extinction in Victoria and New South Wales. The animal moves by gliding from tree to tree: where there are large gaps in tree cover, such as roads, it is unable to cross -- a fact that concerns researchers.

"It is crucial to encourage movement across roads and among squirrel glider populations so that they can access food, shelter and mates," said Dr van der Ree.

"What appears to be happening is that those squirrel gliders who are on opposite sides of the highway are effectively different groups. Despite being just 100 m apart, they might as well be one kilometre or 10 kilometres apart. They have become cut-off from the rest of their group," said Dr van der Ree.

"We are fearful that this could lead to local extinction."

VicRoads Regional Manager for North Eastern Victoria, Bruce Sweet, said VicRoads was eager to see the results once the bridges and poles were installed and its use by wildlife monitored.

"The rope bridge and glider poles will be used to test the effectiveness of such structures in assisting animals to cross the road. This information will then be used by VicRoads in planning future road projects," she said.

As part of the research carried out by Monash University postgraduate Silvana Cesarini between August 2005 and December 2006, a total of 315 squirrel gliders were captured and released in the area. Sixty of these were fitted with radio collars and tracked at sites along the Hume Freeway as well as further from the freeway to provide a comparison.

"We have found that Squirrel Gliders are still quite widespread across the region, despite the level of clearing and number of roads" said Ms Cesarini."However we must work to reduce the threats to survival"

According to the findings, 70 per cent of the gliders tracked at sites with trees in the median strip were observed crossing the freeway compared with 10 per cent crossing where there were no trees.

"Sadly survival rates of animals near the freeway are about one-third less than those of animals living further away," she added.

Other animals likely to use the rope bridge include the brushtail and ringtail possum, yellow-footed antechinus and the brush-tailed phascogale.

Interest in purpose built structures to enable animals to cross roads more easily is increasing in Australia and internationally.

"This project puts Australia at the forefront of international efforts to determine how effective structures, such as overpasses, culverts and pipes really are in enabling animals to move more easily," said Dr van der Ree.