|
Return
to Agenda
Return
to EX15
|
Division(s):
Headington, Quarry, Old Marston, Wheatley
|
ITEM EX15
- ANNEX 3
EXECUTIVE
– 7 SEPTEMBER 2004
A40 HEADINGTON/GREEN
ROAD ROUNDABOUT IMPROVEMENTS
DETAILED
PROJECT APPRAISAL APPRAISAL NO: H178
NAME
OF SCHEME: Signalisation of Green Road Roundabout
BASIS
OF ESTIMATE: Preliminary START YEAR: 2006/07
- DESCRIPTION
OF PROJECT
Transport
Consultants, Faber Maunsell, have devised a scheme that would improve
the efficiency of the whole junction, give buses better access through
the roundabout and reduce current levels of driver uncertainty.
It
comprises the introduction of traffic signals with a dedicated link
through the central island for A40 westbound traffic. The four arms
of the roundabout with the heaviest traffic will also come under signal
control.
Signal
control cannot be accommodated at the Bayswater Road arm, which will
remain as a ‘give way’ entry into the circulating traffic, but gaps
will be generated by the signals on the other arms to allow Bayswater
Road traffic to exit Barton Estate.
(Resource Appraisal - download as
.doc file)
- NEED FOR THE
PROJECT
The
site is difficult to negotiate and has a high accident rate. For example
in 2001-2003 there were 4 serious and 28 slight injury accidents, an
average of over 10 per year. In addition many smaller accidents will
have gone unrecorded. Where similar roundabouts have had signals installed
eg M40 Junction 11 there has been a dramatic drop in accident rates.
The
VISSIM computer simulation of the new layout shows safety advantages
without compromising capacity. The proposed change of layout:
- allows the
heaviest junction flows east and west on the A40 to run together;
- allows the
westbound traffic to move in independent streams through the roundabout,
relieving congestion on the circulatory lanes; and
- allows more
equal access for the London Road and Barton traffic and shortens
the queues considerably on all arms of the junction, thereby improving
bus journey times and reduces non local diversion traffic through
Risinghurst and Quarry.
- CONSISTENCY
WITH THE SERVICE STRATEGY
The
scheme is consistent with policies aimed at accident reduction and
economic vitality. It will achieve capacity improvement on the premium
bus route and will reduce congestion (mainly in the pm peak) on the
radial routes serving the city centre. In specific terms:
- The project
benefits public transport, reduces accidents and also offers some
improvements to pedestrian and cycle facilities and the local environment.
All these accord with the Structure Plan (2011) Policy T11.
- The objectives
"improving safety for all users", "encouraging access by public transport
into the city centre", and "Reducing congestion on radial routes"
of the Oxford Transport Strategy are met.
- The scheme contributes
to and fits within the Premium Route Network Strategy for increasing
bus reliability and patronage. This applies particularly to the Thame
to Oxford (via Wheatley) route.
- OTHER REASONABLE
OPTIONS
During
the period that the Highways Agency controlled the A40 and this roundabout
a number of accident reduction studies were carried out. Some minor
improvements were carried out but these studies failed to produce or
justify a satisfactory signalised layout.
In
the proposed form of signal layout a westbound lane through the roundabout
is essential. Without this feature the same drawbacks that the Highways
Agency experienced trying to signalise the junction simply re-occur.
The scheme Faber Maunsell have modelled is the only scheme that addresses
the main issues both now and in the immediate future with reasonable
success.
During
their design work a conventional roundabout and signal junction were
found to be unsuccessful. A flyover was the only serious challenger
which could deliver improvements although this would be primarily aimed
at non local traffic. It was also mentioned frequently by the public
during consultation. However the cost and disruption of this solution
is much greater. On cost it is estimated to be around 20 times more
expensive.
- LAND
The
scheme is contained within the highway. No privately owned land has
been identified or implicated.
- ENVIRONMENTAL
FACTORS
There
is a small loss of green space in the hub of the roundabout to facilitate
the new lane.
- TIMING AND
PHASING
It
is intended that the main construction should start if possible in spring
2006. Before that some Phase 1 measures already approved to alter the
Oxford bound bus lane to an outbound bus lane on London Road will be
carried out in the autumn of 2004.
If
there is a delay to the main scheme through, say, lack of available
funding in the scheme year, the construction of signal junctions on
Bayswater Road as medium measures may take place, possibly in 2005 ahead
of the main contract.
- FINANCIAL AND
STAFF IMPLICATIONS
This
is a large scheme requiring funding in total of £2.636M. This includes
around £43k already spent on fees and consultation and the separately
approved 2004/05 budget of £207k. This means that the approval sought
in this report for new money is £2,386,000 spread over 2005 – 2009
financial years.
The
scheme delivers economic benefits on both accidents and journey time
savings. The accident savings are based on a predicted 50% reduction
applicable to a new signalised junction at £42,380pa. As there are
5 saved accidents a year this will give an annual saving of £211,900.
In terms of congestion reduction and consequent journey time savings
there are yearly savings of £49,687 in the am peak but much larger
savings annually of £202,169 in the pm peak. If this saving which
excludes elements of off peak savings is added to the accident saving
there is an annual benefit of £463,756. On this basis a comprehensive
construction cost of £2,235,000 will be recovered within 5 years.
DAVID
MCKIBBIN
Head of Transport
CHRIS GRAY
Head of Finance
NEIL MONAGHAN
Head of Property
Contact
officers:
David Clough : Assistant Principal Engineer Tel: (01865) 815743
Stephanie Skivington:
Financial Manager Tel: (01865) 815406
24
August 2004
Return to TOP
|