Highways Agency - Safe roads, Reliable journeys, Informed travellers

Related pages

• Summary
• 1 introduction
• 2 traffic, congestion and safety issues
• 3 geotechnical issues
• 4 environmental constraints
• 5 option development
• 6 options considered further
• 7 engineering comparison of options
• 8 economic comparison of options
• 9 environmental appraisal of options
• 10 waste management
• 11 public open day
• 12 responses from statutory and non-statutory consultees
• 13 conclusions
• 14 recommendations
• Environmental study findings
• Environmental study findings
• Environmental study findings
• Environmental study findings
• Environmental study findings

A417 Cowley to Brockworth Bypass Improvement

Environmental Study Findings

COMPARISON OF OPTIONS

Option 1

Between Cowley roundabout and the Air Balloon roundabout, the road would be widened to dual carriageway with a new section of road bypassing Nettleton Bottom. A modified junction at Birdlip would also be included.

Option 1 would modify the Air Balloon roundabout with traffic signals and provide an additional lane down Crickley Hill. This option has been discarded because:there are serious concerns about the safety of the proposed traffic signals on the Air Balloon roundabout.

• it would only provide short term congestion relief (5 - 7 years)

Tunnel Option

A 2.8km tunnel from Nettleton Bottom to the bottom of Crickley Hill.

A tunnel would remove between 70% and 80% of vehicles from the existing trunk road, and overall the noise and air quality effects on adjacent properties would be improved. However, the existing road would have to be retained to maintain access to County roads and to provide an alternative route should the tunnel be closed in an emergency.

A tunnel would have a number of major drawbacks; it would:

• significantly change the flow of groundwater which could severely restrict and / or contaminate the limestone aquifer (see illustration), which is a major source of water for the area.
• have an adverse impact on many local water abstractions in the area which could severely lessen the amount of water available.
• have, potentially, a very serious effect on Bushley Muzzard Site of Special Scientific Interest at Brimpsfield, a marsh notable for its species richness, including orchids and yellow sedge. A tunnel could reduce the supply of water to this wetland site or dry it out completely.
• require the transport of more than 1.0 million tons of excavated soil to licensed disposal sites.
• have serious operational concerns from the emergency services regarding dedicated services.
• cost an estimated £200M, which represents poor value for money compared with the return for transport and economic benefits.
• have a very high annual operating and maintenance cost of about £6M, compared with about £60,000 for a surface solution (Option 2).

There are so many disadvantages that it has been decided not to pursue a tunnel option further at this stage.

Option 2

Between Cowley roundabout and Air Balloon, the proposed improvements to the A417 are the same as Option 1. In Option 2, the A417 west of Air Balloon would be widened to provide three lanes up Crickley Hill and two lanes down it. The Air Balloon roundabout would be replaced with a two-level free-flow junction. The scheme cost is estimated at £60M.

Option 2 would provide a dual carriageway solution that would overcome the congestion and safety problems on this section of the A417. No unacceptable environmental effects have been identified, it provides good value for money and is deliverable. For these reasons, this option is to be developed further.

Detailed information about the Environmental Study is available in the Study Report.