Highways Agency

• 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

SUMMARY

In October 2001 the Highways Agency appointed WSP Group to undertake an environmental study to examine potential options to improve the A417 between Cowley Roundabout and the end of the Brockworth bypass, Gloucestershire. The aims were to identify the environmental constraints within a study area centred on the existing route, prepare a constraints map and identify if options were available to improve this section of road which did not have unacceptable environmental consequences. In addition, consultation with environmental statutory organisations and "other" local stakeholders was to be undertaken and a public open day organised to provide local people and interested parties an opportunity to discuss the results of the study process.

Background

This section of the A417 has a poor safety record and suffers from severe congestion. This section of the road is the only remaining single carriageway section on the A417/A419 route between the M4 (Jnc.15) and M5 (Jnc.11a). Traffic volumes are currently between approximately 28,000 and 31,000 vehicles per day of which approximately 12-14% are Heavy Goods Vehicles. Queues occur regularly at peak periods.

There are steep hills at Nettleton and Crickley Hill and slow moving Heavy Goods Vehicles (HGV) compound queuing issues. In places the road standard is generally poor with tight bends and narrow lanes. Vehicle shunts occur regularly at Air Balloon and there are accident clusters at Nettleton Bottom, Birdlip, Air Balloon and on Crickley Hill.

Three small scale improvement schemes have been completed recently to improve safety at the Golden Heart Public House, Air Balloon Roundabout and Birdlip junction. A number of additional small scale improvements are also planned in the next few years. However, it is recognised that a longer term solution is required.

Constraints

Environmental and engineering constraints have been identified and translated onto a constraints plan. Information was gathered from a wide range of organisations, from earlier studies and from limited walk-over surveys.

The entire study area falls within the Cotswolds Area of Outstanding Natural Beauty (AONB).

Option Development

Possible improvement options were developed using a staged approach in discussion with environmental statutory bodies, Local Authorities and other Stakeholders. A number of options were initially identified which have been systematically reduced on assessment of data collected or on the advice of those consulted.

As a result of this process three options remain. Two of these are on-surface options that only differ in their treatment of Crickley Hill and the Air Balloon Roundabout. The third is a tunnel option which would pass between Nettleton Bottom and the foot of Crickley Hill. The options are summarised below:

• 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. An additional lane would be constructed down Crickley Hill and the Air Balloon roundabout modified with traffic signals.
• Option 2 - Carriageway as for Option 1 but with the Air Balloon roundabout replaced with a grade separated junction and an additional two lanes down Crickley Hill (providing a 3-up, 2-down arrangement).
• Option 3 - A tunnel extending from just north of Cowley roundabout down to the foot of Crickley Hill.

Option Assessment

Engineering Comparison

All three options are buildable, although Options 2 and 3 would cause less disruption during construction to vehicle flows up Crickley Hill. In addition remodelling of the Air Balloon roundabout under Options 1 and 2 would cause disruption while the schemes were built.

Options 1 and 2 would retain steep gradients on Crickley Hill (in the order of 10%). Option 3, the tunnel, would have an average gradient of 4.4%.

Option 1 would require departures from standards, however, there are safety concerns with the signalised junction which cannot be overcome by careful detailed design and for this reason Option 1 should be discarded. Departures from standards would be required on Option 2 but safety would not be compromised. Option 3 would not require departure from standards.

Temporary contractors camps would be required for all three options, although these would be potentially larger for Option 3. Option 1 would take less than 2 years to construct, Option 2 would take approximately 2.5 years, and Option 3, 3 years or more (depending on hydraulic conditions encountered).

Option 2 would have a severe impact on properties.

Economic Comparison

The preliminary economic assessment has identified that all options have positive Net Present Values (NPV's) at high growth. Options 1 and 2 have positive NPV's at low growth whereas Option 3 is negative. All three options contribute time savings and reduction in accidents.

Option 1 would be the least expensive option at approximately £40 million, but has the least benefits and would only provide a short to medium term improvement for relief of congestion. Option 2 represents best value for money as it has the highest NPV's and Benefit/Cost Ratio. This option would cost in the region of £60 million. Option 3, at a cost of approximately £200 million, has the greatest benefits but due to the anticipated tunnelling costs is also the most expensive.

Environmental Comparison

An environmental appraisal of the three options has been undertaken using the Guidance on the Methodology for Multi-Modal Studies (GOMMMS) approach.

In terms of landscape, Option 1 would have a moderate adverse impact on the AONB and landscape character, whilst both Options 2 and 3 would have large adverse impacts, the latter due to the link roads and portals particularly at the northern end.

Cultural and archaeological resources are many and varied within the study area. Options 1 and 3 would have slight adverse impacts whilst Option 2 would have a moderate adverse impact, mainly due to its affect on the context of Crickley Hill.

In terms of ecology, the two surface options largely avoid nationally and locally designated sites. However, dewatering for the tunnel may potentially severely affect Bushley Muzzard SSSI which relies on spring water. It is possible that mitigation measures could be designed to minimise impact. However, given the uncertainty at this time, there remains a high risk of permanent damage and a very serious adverse impact has been predicted for Option 3.

Water in the underlying Major Aquifer is a major issue in the study area and its presence has had a major impact on previous road schemes in the study area. Mitigation measures for Options 1 and 2 could reduce the impact on the water regime such that the long term impact on the ground and surface water regime is predicted to be slight adverse. However, there is considerably more risk about the potential impact of the tunnel and the Environment Agency have expressed serious concerns. The tunnel option, therefore, has been awarded a large adverse impact score.

In terms of local air quality, Options 1and 2 would increase localised air pollution although along the whole route there would be an overall decrease. Under Option 3 overall local air quality would improve, although the pollutants would be concentrated at the tunnel portals. Both Options 1 and 2 would also lead to an increase in the release of greenhouse gasses, whilst the tunnel option would lead to a decrease.

Up to 29 properties would experience an increase in noise levels under option 1 and 4 properties would experience a decrease in noise levels. Under Option 2, up to 32 properties would experience an increase and 6 a decrease in noise levels. Under Option 3, 12 would experience an increase in noise and 37 a decrease.

Public Open Day

A Public Open Day was held in Birdlip Village Hall on the 15th and 16th of February 2002. It was attended by approximately 200 people, including Local Councillors, MP's and local residents. Members of the consultants team and the Highway Agency were present to answer questions.

The issues raised and discussed related to:

• Rat-running (people using small local roads to avoid queues on the A417);
• Access to local properties (especially related to Cold Slad Lane and other properties on Crickley Hill);
• The tunnel option - Many people were interested in the costs of the tunnel and the environmental benefits and disbenefits identified by the preliminary assessment. Few expressed a preference for the tunnel on the day, although most correspondence received since the Open Day has been pro-tunnel. Some visitors to the Open Day expressed the view that the information presented was biased against the tunnel. Several visitors commented on the lower gradient in the tunnel compared to the existing road up Crickley Hill and the benefits a tunnel would have in times of severe weather; and
• Surface options - These comments ranged from those in favour of re-modelling of the existing road rather than building new roads to those expressing concern over all, or part, of the route.