Agenda item

Report ES19033

Approval was sought to construct a raised table at the mini-roundabout junction of Loop Road and Ashfield Lane, Chislehurst in response to a number of collisions at the junction and their pattern. The mini-roundabout has been a particular safety concern for many years; the carriageways of Ashfield Lane and Loop Road at their intersection in the middle of Chislehurst common are narrow, carrying a reasonably high volume of traffic, including buses. Vehicles are often seen over-running corners or being driven close to the edge of the carriageway.

The mini-roundabout was originally implemented to reduce collisions and speed at the junction but personal injury collisions have continued even though further alterations have been made e.g. realignment to the kerbs for increased deflection and buff surfacing on approaches.

The general arrangement for the proposed table was outlined in draft drawing 12893-01 Rev B appended to Report ES19033. Although the Council has a preference for non-vertical schemes to reduce speed, following past implementation of a number of schemes and with no viable new alternative apparent to reduce injury collisions at the junction, consistent with policy one was proposed in this instance. A raised table would slow vehicles at the mini-roundabout and afford drivers increased time to assess whether a manoeuvre is safe. A “virtual” speed table (coloured road surface through the junction) was considered but assessed as less likely to sufficiently improve driver behaviour. Changing priorities at the junction to give way lines on Ashfield Lane was also considered as was a priority give way feature on the Eastern arm (or both arms) of Ashfield Lane to reduce traffic speeds approaching the junction. Closing a section of Ashfield Lane was additionally considered. However, the proposals would create additional congestion on the common, particularly during busy times of day.

Bollards will be required to deter vehicles from over running the footway given a very low upstand between the kerb and carriageway from a raised table. With the bollards needing to be 450mm from the kerb edge, the footways will need widening slightly at the junctions to allow pedestrian access, particularly pedestrians with mobility issues and push chairs. Initial approval has been received from the Trustees of Chislehurst Common to use small amounts of Common Land for the footway widening. Before the scheme is implemented, the detailed design will need to be approved by the Trustees.

The proposal is estimated to cost £60k funded from the £574k allocation for casualty reduction and road danger reduction in the 2019/20 LIP budget agreed by TfL. Future maintenance costs would be contained within existing highway maintenance budgets.

Cllr Kieran Terry (Chislehurst Ward) provided a short PowerPoint presentation supporting the proposed scheme. Details are at Appendix C. The Assistant Director, Traffic and Parking, indicated that no other cost effective solutions can be provided - cost benefit being taken into account. Supporting the proposed solution, including slightly extending the roundabout into the junction road arms, a Member indicated that drivers can be in the position of not realising the junction comprises a mini-roundabout.

Reminding the Committee of Council policy to avoid vertical deflections, unless for exceptional circumstances, a Member suggested give-way stops at the junction instead of a mini-roundabout. However, there were doubts on whether give-way lines would have any (positive) effect and might be a backward development - the junction having originally been changed from give way lines to a mini-roundabout to improve safety. Cllr Terry also felt that give-way lines would not be workable, envisaging a tendency for drivers to speed when exiting the junction towards Green Lane and Heathfield Lane. Cllr Terry also referred to queuing on short arms of the junction.

Concerning views from emergency services on the scheme, no feedback had been received from the London Ambulance Service and the Metropolitan Police raised no objections. Bus companies also raised no objections. 

Cllr Terry indicated that the roundabout would be too small for rumble strips and the scheme would be sited in a conservation area. The Assistant Director also indicated that nearby housing is not sufficiently distanced from bona-fide rumble strips; rumble strips are required by regulation to be a certain distance from housing given noise concerns from vehicles traveling over the strips.

It was suggested that signage at the roundabout needs to be reviewed as mini-roundabouts can be easy to miss when driving; some drivers might also be tempted to deliberately drive fast over them. Advice was also sought on whether the signs are too close to the roundabout and whether consideration had been given to changing the roundabout’s colour. It was confirmed that the signs are required to be placed at the roundabout and a permanent advance warning of the raised table would also be provided to help reduce speeds. It was also explained that different materials can be used for the roundabout providing a different colour. These are also longer lasting although some materials/colours need more maintenance than others. Reference was made to a buff colour for the roundabout which the Assistant Director supported if it draws the attention of drivers to the roundabout. 

RESOLVED that the Portfolio Holder be recommend to:

(1)  approve construction of the raised table at the roundabout junction of Loop Road and Ashfield Lane due to the ongoing incidence of injury accidents, notwithstanding previous interventions at or around the junction;

(2)  authorise allocation of £60k from the LIP casualty and road danger reduction budget to enable completion of this project during 2019/20; and

(3)  delegate authority to the Executive Director of Environment and Community Services, in consultation with the Portfolio Holder and Ward Members, to approve the scheme’s detailed design.