Supplementary memorandum by the Highways
Agency (RP 52A)
ROAD PRICING: FOLLOW-UP
In reply to the letter of 15 February to Archie
Robertson asking for additional information in the light of the
hearing he attended with Hilary Chipping on 2 February, Archie
has asked me to send you the following. He hopes they will be
of use to the Committee.
Q644: Please could you advise the Committee
what action has been taken and what action will be taken to deal
with the localised congestion problems emerging at either end
of the M6 Toll, where the road re-joins the Highways Agency motorway
network. NORTHERN END
OF M6 TOLL
At the northern end of the M6 Toll (Junction
11A of M6) three lanes of the M6 need to merge with three lanes
of the M6 Toll, then merge into the existing three lanes to the
north of Junction 11A. The final design of the M6 Toll limited
capacity at this location to three lanes only.
During the design of this interface a unique
design was adopted for the northbound carriageway that involved
taking lane three off the M6 early to join with the M6 Toll. This
has assisted to a degree with the predicted flows, but over the
last few weeks there has been some congestion between Junction
11A and Junction 12. Traffic at this location will be carefully
monitored over the next few months to determine if the congestion
dissipates or increases. In the light of that the Agency will
come forward with suitable proposals for mitigating any continuing
congestion.
SOUTHERN END
OF M6 TOLL—SOUTHERN
CARRIAGEWAY
Through Junction 8 of the M42 there are columns
carrying the M6 over the M42/M6 Toll shared section. This allows
only four lanes at this location; two dedicated to the M42 and
two to the M6 Toll. A schematic layout is attached at A.
Congestion on the southbound carriageway at
this location has been experienced almost from the onset of opening
the M6 Toll. Observation of flows along the shared section of
the M42/M6 Toll indicate that there is a substantial amount of
traffic coming off the M6 Toll wishing to go down the M42. As
the flows on the M42 are substantial there is very little capacity
in lanes one and two to take the traffic trying to enter from
lane three. A further problem is the fact that the M42 at the
diverge has been built as a two lane facility and is already nearing
capacity. The latter situation is presently under discussion with
Midland Expressway Limited (MEL).
As an interim measure to improve flows south
of Junction 8 the Highways Agency has temporarily closed off one
lane of the two lane M6 Southbound slip. This has assisted flows
to a degree at the interface with M42 where there exists three
lanes, but is obviously not the complete solution to the congestion
experienced in the am peak.
It has also been noted that of late, the work
to the south of Junction 7a (M42), associated with the implementation
of ATM, is now having an impact on this section of the M42/M6
Toll. However, this work is due to finish at the end of March
2005 and flows should therefore improve to the south of Junction
7.
To achieve a solution and ease traffic flows
the Agency is currently investigating in conjunction with MEL
a possible pilot to increase capacity on the two lanes of the
M42 where it diverges from the M6 Toll by using the hard shoulder
and narrower lanes over this short section. At the same time to
seek further improvements there will also be realignment of the
merge to the north of Junction 8 where the M42 joins the M6 Toll.
If this proposal is agreed with MEL it could be implemented over
the 2005 summer period. Once the pilot has operated for a 12 month
period and all parties are satisfied that it has worked then the
Agency would look at methods of making three full lanes along
this section of the M42
Q655-6: You offered to make available to
the Committee information regarding hard shoulder running and
the safety assessment. We would be grateful if you could provide
this information.
Attached are a series of documents covering
the Agency's safety strategy for the M42 ATM pilot, the Dutch
experience of hard shoulder running and access for emergency vehicles
in the event of an incident. To assist the Committee a summary
of these documents is also provided.
Q657: In discussing the High Occupancy Vehicle
lanes you referred to assessments of the flow benefits that would
be achieved by introducing HOV lanes on an existing three-lane
motorway, as well as where roads are widened. Please could you
provide details on the expected benefits from both types of scheme.
The principal benefits from introducing an HOV
lane are associated with:
(i) the time savings for High Occupancy
Vehicles;
(ii) the reduction in general levels
of congestion associated with people leaving their car at home
and travelling as a passenger; and
(iii) the operating costs saved as
a result of the car being left at home.
A monetary value is routinely put on benefits
such as these as part of well-established DfT cost benefit analysis
(COBA).
As part of a feasibility study into HOV lanes
on English motorways, our consultants developed two generic models.
These sought to assess the benefits that would accrue if a 10
km length of HOV lane was introduced on a three-lane motorway
and on a four-lane motorway at a range of traffic flows. The results
of this assessment are shown in figures 1 and 2. The assessment
is generic and does not allow for any site-specific factors, such
as whether the HOV lane is being introduced as part of a widening
scheme.
It can be seen that for the dual three-lane
motorway benefits are positive if 10 to 15% of traffic is removed,
and the benefits increase with higher flows. For 5% removed traffic,
the benefits are positive for lower flows, these peak at around
4,000 vehicles per hour and become negative at carriageway flows
above 6,000 vehicles per hour.
For a dual four-lane motorway, the benefits
are positive for all flow reductions in the range of 5 to 15%
and increase with traffic flow.
Experience in Leeds and the United States indicates
that the introduction of an HOV lane could reduce traffic flows
by about 10%. We have used this as our central estimate, for example
in considering the proposed HOV lane on the M1 between Luton and
St Albans. However, given the uniqueness of the proposal within
England, we have also looked particularly critically at the expected
impacts if conversion rates were low, eg 5%. At this level the
graphs indicate that for four-lane motorways the economic benefits
are positive at all realistic flow levels. However, on very busy
three-lane motorways the benefits start to decline once flow levels
exceed about 4,000 vehicles per hour.
The current traffic flow levels for each site
investigated are also annotated on the figures to indicate the
level of benefit likely to occur to them (albeit for a standard
10 km length).
As well as this general assessment information,
there is evidence from the States that (a) schemes involving the
conversion of an existing lane to an HOV lane, and (b) HOV lanes
on dual three-lane motorways have not worked well and have had
to be abandoned.
March 2005
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