The bypass, which opened in 1988, was built through sensitive wildlife-rich areas in Berkshire despite protests from green groups.

All roads should receive the 'Newbury' treatment

Dr Neil Ward

Special features such as pollution-minimising ponds were put in place to help minimise environmental damage.

But environmental groups say the study raises questions about the impact of other new roads if similar safeguards are not applied.

'Balancing ponds'

The latest research, by experts from Surrey University, studied the effects of the Newbury bypass over a three-year period.

Scientists monitored the effects of lorries, cars and buses using the nine-mile bypass, which lies to the west of Newbury.

Samples of pond sediment, roadside deposits and waterways were taken before and during construction and after the opening of the road in October 1998.

Every sample was listed and analysed for pollutants such as heavy metals, lead and cadmium.

The report says while the "balancing ponds" are effective in cutting down pollution they need monitoring and management to be completely successful.

The findings presented by the Berks, Bucks and Oxon Wildlife Trust (BBOWT) in association with Newbury's Campaign of Businesses for Environmental Protection (CAMBUS) and Dr Neil Ward of Surrey University, show a steady accumulation of heavy metals in the ponds.

Environmental concern

Where the ponds are poorly established, they release contaminated sediment into water courses, namely the Kennet and Lambourn rivers.

And the level of contamination discovered would suggest that the existing UK network of roads are severely polluting their surrounding areas.

Martin Spray, director of BBOWT, said the level of pollutants were cause for concern.

But he added: "It is my hope that this project will serve to ensure that environmental impact will be a priority factor in determining the viability, location or form of any future road scheme or other significant development.

"Newbury Bypass is unique in its level of pollution-minimising features - other roads by comparison are still in their infancy and likely to sustain huge amounts of heavy metal pollution."

Dr Neil Ward said: "From my experience, all new roads should receive the 'Newbury' treatment.