Return to Agenda

ITEM EX6

GREEN ROAD ROUNDABOUT, HEADINGTON – IMPROVEMENT OPTIONS

1. The Local Transport Plan and work on the Headington and Marston Area Transport Strategy have identified the need for improvements at the Green Road Roundabout, Headington, aimed at reducing traffic congestion, improving bus priority and journey times and addressing accident and safety issues. Consultants Faber Maunsell were appointed to carry out a study of the roundabout and this report reviews the consultants’ suggested options with a view to identifying possible short/medium/long term improvements.

Background

2. The A40, including the Green Road Roundabout, was a trunk road which was the responsibility of the Department for Transport until April 2002 when it was transferred to Oxfordshire County Council. The roundabout has been improved several times by the Department of Transport over the years and consideration was also given to an alternative means of improving congestion here by providing an A40 Barton northern bypass. The latter was ruled out principally on environmental grounds. The Department of Transport also considered an A40 flyover or underpass at the roundabout but again these were discounted at an early stage because of the cost, disruption to pedestrians and detrimental environmental impact on local residential properties.
3. Local County and City members, together with County Council officers, had long felt that there could be less expensive and less environmentally damaging options available and therefore a commission was issued in May 2003, immediately following the detrunking, for a detailed traffic study to be undertaken by the consultants, Faber Maunsell.
4. Faber Maunsell provided an interim report in October 2002. Officers felt that some additional information and clarification was required and Faber Maunsell were asked to prepare a final report for February 2003. This has now been received (a copy is in the Members’ Resource Centre) and is summarised below.

Synopsis of Faber Maunsell Traffic Study Report

5. The Faber Maunsell report is a comprehensive report on their investigations and findings on the complex Green Road roundabout. It provides background to and analysis of the existing situation and sets out the aims and objectives as agreed with the County Council officers. A number of options are investigated in the light of the aims and objectives and recommendations put forward. The key objectives of their report were to assess options that would:

• reduce queuing and delay for all the traffic at the roundabout;
• provide improved bus priority and reduce bus journey times through the roundabout; and
• reduce the likelihood of accidents.

6. Faber Maunsell’s report has set out the results of their investigations into the current situation at Green Road roundabout and it highlights the existing traffic problems. The results and analysis confirm that the traffic demand at the roundabout is greater than its current capacity during both peak periods. There may also be other traffic that presently takes alternative routes to avoid the congested roundabout – officers are aware of ‘rat running’ through estate roads in Risinghurst and also further afield through Headington Quarry, Wheatley and Water Eaton. This ‘suppressed demand’ could revert to the Green Road roundabout if improvement measures create a significant reduction in the present congestion.
7. Their report considers a number of possible improvement options that tackle accidents, delays and congestion and bus priority. It contains robust discussion and analysis of the options and includes supportive data and plans.

Accidents

8. The Council’s accident statistics show that this junction is top of the ‘black spot’ list in the County for numbers, although the severity rate is low. However the consultants’ view is that the 3-year accident rate is no higher than would be expected from this type of complex 5-legged roundabout and the accident rate is average given such high traffic flows. To reduce accidents, they have suggested certain road safety measures that could be provided in the short-term. These are anti-skid surfacing, amended road marking and enhanced signing. These measures need to be considered in the light of any medium and long term measures that may be introduced. They would not, on their own, reduce congestion or improve journey times.
9. Faber Maunsell conclude that the existing underground pedestrian and cyclist facilities are well used, in good condition and offer a safe environment. Any attempt to provide ‘at grade’ (at existing ground level) crossings, with any of the considered options, would result in a detrimental impact on general traffic and bus services.

Options to Relieve Congestion

10. Faber Maunsell investigated seven options which they thought would relieve congestion. These varied between widening the approach widths, signalisation of the existing roundabout, conversion into a signalised junction and modifying the present layout to form a Hamburger Roundabout. (A ‘Hamburger Roundabout’ is a relatively new development whereby the roundabout is signalised but also introduces a straight-through section of carriageway for one of the major routes – this creates a plan view somewhat like the cross-section through a hamburger) The analysis of a signal-controlled roundabout on its present layout (see Annex 1) (download as .doc file) indicated that this would not relieve the present congestion or improve bus journey times because there is insufficient space available within the roundabout, which would result in the worsening of the current situation. Similarly, converting the roundabout to a signal-controlled junction produced results that indicated that the junction would operate at over capacity with severe queuing and delay on all arms except London Road.
11. A full grade-separation option was also considered and the consultants have concluded that only this and the A40-A40 ‘hamburger’ option meet the aims and objectives set out in the traffic study. As Faber Maunsell point out, the grade-separation option is significantly more expensive (it could cost upwards of £40M) than the hamburger roundabout (approximately £2M). The grade-separation junction would require land acquisition outside the highway boundary and it would have severe environmental impact on the area around the existing roundabout. An economic assessment of these two options shows that the hamburger roundabout is more cost-effective and would therefore deliver better value to the Council. (An illustration of the proposed layout of the hamburger roundabout is shown in Annex 2) (download as .doc file).
12. Any scheme greater than £5m would be regarded by the Department of Transport (DfT) as a major scheme and would be subject to a separate bid for funding. It is doubtful whether a £40m scheme could be justified and in any event would take many years to complete.
13. ‘East-west’ and ‘north-south’ hamburger roundabouts were also considered and rejected on the grounds of reduced capacity, increased congestion and increase in bus journey times.

Options to Enhance Bus Priority

14. Several options were considered by Faber Maunsell for improving priority for buses travelling through the roundabout. These options are described and discussed in their report and three options are recommended for implementation with an additional one if the hamburger roundabout scheme was to be constructed. These are:

• To close the exit from the Roundway service road, just west of McDonalds, into the A40. This will remove the conflict of ‘queue-jumpers’ on the A40 using the service road to get to the front of the queue at the roundabout;
• To provide a bus lane on the A420 London Road eastbound. This will reduce delays for buses leaving Oxford centre. This option will have to consider the effects on the existing westbound bus lane and cycle facilities;
• To provide traffic signals at the junction of Bayswater Road and Waynflete Road. This will facilitate buses exiting Waynflete Road to joint Bayswater Road, especially in the morning peak period when queuing or slow moving vehicles approaching Green Road roundabout block this junction; and
• To provide a bus pre-signal on the westbound A40. This will allow an improved level of bus priority approaching the roundabout, especially for the Thornhill Park and Ride buses.

Recommendation by Faber Maunsell

15. Faber Maunsell have carried out detailed assessments into various options for the improvement of the Green Road roundabout. They conclude that the option that will best meet the aims and objectives of the brief in the long term is the provision of a ‘hamburger roundabout’ as shown in Annex 2. This preferred option does not require land outside the highway boundary, should have relatively small environmental impact, is best suited to relieve congestion, is complementary to safety improvement measures and when combined with suggested bus priority measures, provides the best option to reduce bus journey times.
16. Faber Maunsell also suggest measures for short and medium term that could be implemented independently, yet complement each other and lead to the construction of a long term solution. These are:

• Short term – closing the accesses to the A40 from The Roundway, improved signing, anti-skid surfacing and, in case a preferred long term solution is not accepted, spiral road markings.
• Medium term – an eastbound bus lane on the London Road approach and signalisation of the Bayswater Road/Waynflete Road.

17. The officers have studied the report by Faber Maunsell and they are encouraged that the hamburger roundabout offers an opportunity to improve the Green Road roundabout by reducing congestion and improving bus journeys. More work is needed by the consultants to develop the scheme and its detailed implications on buses, buildability, etc.
18. It is clear that there is a significant level of suppressed demand for travel through the junction. Increased capacity at the junction would be likely to fill quickly and would have limited benefits because of the restricted capacity of adjacent junctions. However, capacity improvements at the roundabout would provide the valuable opportunity to provide bus priority and manage traffic with signals, without detriment to general traffic conditions overall. There would be safety benefits both at the roundabout and on other routes that are currently used as alternatives.

Proposed Programme

19. The officers agree with the suggested three stage approach of improvements at the roundabout and its vicinity. Subject to the approval of the 2003/04 Transport Capital Programme, £50,000 will be allocated from the developer contributions in the HAMATS area. That would enable the implementation of the described short term measures in summer 2003 and to start the preliminary design work on the medium and long term solutions, followed by the first round of consultation.
20. Following this consultation the medium term measures can be designed in detail and implemented in early 2004. At the same time a second round of consultation on the long term solution can take place with a view to finalising its preliminary design. It is intended to report the outcome of this further consultation and a final detailed layout to the Executive with a view to it being considered for inclusion in the 2004/05 and 2005/06 capital programmes for the start of construction in early 2005.
21. An illustration of the proposed programme for improvements to the Green Road roundabout in shown in Annex 3 (download as .xls file).

Environmental Implications

22. Measures to reduce congestion and improve bus journey times will improve the environment in and around the Green Road roundabout. The detailed design will seek to incorporate measures that mitigate traffic delays associated with the construction of a hamburger roundabout and its overall environmental impact.

Financial and Staff Implications

23. Current investigation is financed from the 2002/03 Capital Programme. However no funding presently exists for any future improvement to this roundabout. If the Executive favours a scheme in principle, it would need to compete against other potential commitments for a place in the Transport Capital Programme. However, a provisional sum of £50,000 has been allocated in the proposed 2003/04 OTS Programme from developer contributions in the Headington area. If successful, this would enable funds to be provided for design fees in order to develop the scheme further, and for implementation of short term measures identified in this report. Any further development and implementation of the medium and long-term measures will need to be a subject of future year Capital Programme funding allocation.

RECOMMENDATIONS

24. The Executive is RECOMMENDED to:

1. approve the long term measures shown on drawing No 30510/P001 in Annex 2 to the report as the preferred scheme for further development and consultation;
2. approve the implementation of the short and medium term measures set out in paragraph 16 of the report, subject to inclusion of the schemes in the Transport Capital Programme and the consideration of any observations or objections resulting from consultation on the individual measures by the Transport Implementation Committee.

DAVID YOUNG
Director of Environmental Services

Background papers: Report entitled ‘Green Road Roundabout – Improvement Options Report’ by Faber Maunsell dated February 2003

Contact Officer: Peter Evans, Tel: Oxford 815836

February 2003

Return to TOP