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ITEM CA11

CABINET – 17 JANUARY 2006

OXFORD EASTERN BYPASS - STUDY OF POSSIBLE ROAD SAFETY MEASURES

Report by Head of Transport

1. The Cabinet Member for Transport requested that a safety study be carried out following the tragic multiple fatal accident on 28 May 2005 and the widespread concern that followed, including a resolution on a motion to Council on 21 June 2005. An interim report was considered by the Cabinet on 6 September at which it was agreed that:

• A 50mph speed limit on the entire length of the A4142 Oxford Eastern bypass would be promoted, with any objections being considered by the Transport Implementation Committee in the usual way.
• A central barrier should be provided on the length between Kiln Lane and Horspath Driftway (subject to the cost not exceeding £600,000).

2. At the meeting of the Transport Implementation Committee on 22 December the responses to the consultation on the 50mph limit were considered and it was agreed to proceed with making the speed limit order advertised.
3. Detailed design work for the provision of a central barrier between Kiln Lane and Horspath Driftway has identified that the overall costs of these works will be £680,000 but approval has been obtained to proceed with this scheme at this extra cost. A special deign was required because of underground services in the centre reserve. Works are planned to start in late January 2006.
4. Jacobs Babtie have now submitted a final report of their safety study for the A4142 between the A40 Headington Roundabout and B480 Garsington interchange and this report presents the results of this study. A copy of the full report has been put in the Members’ Resource Centre.

A4142 between A40 Headington Roundabout and Kiln Lane

5. The consultants’ analysis of the accident history identified no record of injury due to cross-over collisions. The cost of providing a central barrier is estimated to be £100,000 (it is likely that a conventional steel barrier can be used as there do not appear to be any significant problems with underground services). Further design work would however be needed to confirm costs.
6. The economic assessment of the benefits of this work shows a very low rate of return given the absence of cross-over accidents in recent years (a barrier might however serve to deter pedestrians crossing over this length – in 2004 a fatal pedestrian accident was recorded near the Beaumont Road junction). Current standards for new roads would require the provision of a safety barrier taking account of the speed limit and width of the central reserve but it is not mandatory to install on existing roads to make them comply with current standards, and a risk assessment approach is accepted in these cases.
7. The majority of the other accidents on this section comprise shunt type collisions on the northbound approach to the Headington roundabout and the southbound approach to the signals at Kiln Lane junction. Major works are programmed at Headington roundabout and it would be appropriate to defer any consideration of remedial measures on the approach to the roundabout until after this work has been completed and evidence gathered on the safety performance of the new layout.
8. This length is already subject to a 50mph limit and lighting is provided to current standards.

A4142 between Kiln Lane and Horspath Driftway

9. As referred to above, a central barrier is to be provided on this length in early 2006 in response to the tragic accident on 28 May and the previous history of cross-over accidents which, although limited, nevertheless suggests that there is an appreciable risk of further cross-over accidents from time to time. Approval has also been given to the introduction of a 50mph limit. This will extend from the current termination of the 50mph limit south of Kiln Lane, to the junction of the A4142 with the A4074 and A423 at Heyford Hill roundabout, justified by the accident record on the whole length of the Eastern by-pass. Together these measures should help appreciably improve safety and it is recommended that their effectiveness is monitored before consideration is given to any other measures. It should however be noted that this length of the A4142 has no street lighting and the proportion of accidents in darkness is above average; this may point to a need to consider the provision of street lighting if future monitoring of the accident history suggests this would be a cost effective means of improving safety.
10. Concern has been expressed about safety of pedestrians crossing the A4142 where two rights of way cross the road. However no injury accidents have been reported involving pedestrians at these locations, and it is considered that diverting pedestrians to safer crossing points would cause appreciable inconvenience; the design therefore provides gaps for pedestrians through an overlap layout of the barrier at these points. The provision of warning signs for traffic of the possible presence of pedestrians crossing will be included in the scheme.
11. Remedial measures were introduced at the A4142 junction with Horspath Driftway in 2003 to address a high accident frequency here; preliminary monitoring indicates that the frequency of accident has reduced by approximately 30%.

A4142 Between Horspath Driftway and Garsington Interchange

12. A review of the long term accident history on this length shows a very limited number of cross-over accidents. The layout of the central reserve varies substantially within this length; between the Horspath Driftway and Horspath Road junctions, the overall dimensions are similar to the adjacent length to the north, though with less extensive underground services, so, for most of the length through to the Horspath Road junction, a conventional steel barrier would be feasible.
13. However, the narrow width of the central reserve over the majority if the length south of the Horspath Road junction does introduce constraints which can only be realistically accommodated by accepting a departure from standards in relation to the set-back distance of the barrier from the edge of the carriageway.
14. The preliminary cost estimate for providing a barrier on this length is £400,000; the economic assessment shows a very low rate of return taking account of the very limited number of relevant accidents in recent years. The possibility of incorporating the provision of a barrier with maintenance works (so as to minimise the cost of the works and also disruption to traffic) has been explored but there are no suitable works currently programmed.
15. As with the length to the north of Kiln Lane, current standards would require (in the case of a new road with this layout) the provision of a safety barrier taking account of the speed limit and width of the central reserve.
16. The 50mph limit has been approved which should reduce the risk of all accidents, including those involving cross-overs. It should also be noted that remedial measures were introduced at the junction with Horspath Road in 2003 and preliminary monitoring indicates that the accident frequency at the junction has reduced by around 40%.

A4142 Between A4158 Rose Hill Roundabout A423 Heyford Hill Roundabout

17. The consultants’ report did not include an assessment of this length (which also does not have a safety barrier but does have a substantial hedge along the central reserve); this will be assessed separately along with the small number of other lengths of dual carriageway in the county where barriers are not provided in accordance with current standards as called for in the resolution on the motion to Council on 21 June. The results will be reported in 2006.

Conclusions

18. The economic case (taking account the estimated costs and likely accident savings) for providing a central barrier on the lengths of A4142 between the A40 Headington Roundabout and Kiln Lane, and between Horspath Driftway and the Garsington Road interchange is very low.
19. Between Headington roundabout and Kiln Lane, the risk of a cross-over accident is judged to be low due to the constraint on speeds placed by the junctions at each end of this relatively short stretch of road, together with the slight mounding of the central reserve. A barrier however might serve to deter pedestrians from crossing the road away from the safe crossing facilities provided at each end of this length.
20. Between Horspath Driftway and Garsington Road the actual risk of a severe crossover accident are judged to be higher; however notwithstanding this the economic assessment indicates that considerably greater accident savings would be achieved by expenditure on other schemes offering higher rates of return; it should also be noted that the planned 50mph limit should help reduce overall accident frequencies.

RECOMMENDATIONS

21. The Cabinet is RECOMMENDED to:

1. agree that on the basis of current evidence further safety fencing or other measures on the A4142 Oxford Eastern bypass in relation to cross-over accidents are not required as ‘stand alone’ schemes;
2. ask officers to consider the opportunity to provide further safety measures to prevent cross-over accidents when other major works are being planned on the bypass;
3. note that monitoring of road casualties will continue as normal and may justify other types of casualty reduction measures on the bypass.

STEVE HOWELL
Head of Transport

Background papers: Jacobs Babite A4142 Safety Study Final Report

Contact Officer: Anthony Kirkwood, Assistant Principal Engineer, Tel: 01865 815704

January 2006

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