3 The deployment of measures to tackle
congestion
14. The Agency uses conventional cost benefit analysis
to assess the merits of its schemes regardless of their type,
applying the analysis to major road construction projects as well
as smaller, individual projects involving the installation of
technology or other measures to tackle congestion. It had been
unable to prove a sufficiently compelling business case for many
of the traffic management measures it had tested at individual
sites on the network. By comparison, authorities in the Netherlands
did not prepare a separate business case for every installation.
Instead they undertook a broader evaluation of the potential value
of particular measures, and hence had adopted measures more widely
than the Agency.[14]
15. Where the Agency has tested measures such as
ramp metering and variable speed limits, it has managed the trials
poorly which has contributed to some trials' inconclusive results.
The Agency had not issued any guidance on identifying, designing
and delivering its trials, or on how long trials should take or
how much they should cost. The Agency could sharpen the management
of its trials by drawing on the principles identified in the Report
by the Comptroller and Auditor General (Figure 2).[15]
Figure 2:
Best practices for designing, managing and delivering trials of
measures to tackle congestion
In designing a trial, the Agency should:
- take account of trials carried out in other countries, systematically assessing the results of any evaluation or research on those trials' results and any lessons to be learned in adopting the measure under trial;
- set clear objectives for the trial, with a clear budget and timescale. Trials should have a finite life with a fixed end date. Two years, for example, would allow for two annual cycles of traffic flows and any seasonal variations.
In establishing a trial, the Agency should:
- select sites that will not be affected by any other planned changes, such as the introduction of other forms of technology not under trial or changes in road layout, that would compromise the evaluation of the trial;
- collect sufficient and reliable traffic-related data before the trial begins; and
- put in place procedures to collect sufficient and relevant traffic-related data during the course of the trial that are consistent with the data collected before the trial started.
In managing a trial, the Agency should:
- monitor the progress and results of the trial on a regular basis; and
- evaluate the results of the trial, including the impact of the measure itself and the design, management and delivery of the trial. The evaluation should include an assessment of: the factors contributing to or detracting from the trial's success, including the characteristics of the trial sites such as traffic volumes and patterns, in order to identify lessons for future trials; and of whether the measure should be adopted elsewhere on the network and, if so, under what conditions.
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Source: National Audit Office
16. The Agency has not integrated its technology
strategy with its road building and widening strategy. The Agency
had installed the most sophisticated technology, the Motorway
Incident Detection and Automatic Signalling (MIDAS) system, mainly
on motorways around the major conurbations in the North and the
Midlands and along the M1 and M6. The system had not been implemented
on many of the heavily congested motorways in the South East.
Over three-quarters of its variable message signs had also been
installed in the North and the Midlands (Figure 3). By
contrast, some 70% of the motorway network, including parts of
the M25 motorway, was still served by only the most basic electronic
message signs, indicating conditions such as "fog" or
a speed restriction. The Agency considered that resources had
been a limiting factor, although it would be expanding implementation
of its more sophisticated technology across the network over the
coming years. Provision in the South East should catch up with
other regions as enhanced technology was established during the
widening of the M1 and M25 for example.[16]Figure
3: Installation of MIDAS systems and variable message signs, by
region
| Region
| Kilometres of motorway covered by MIDAS
(per cent of total)
| Number of variable message signs installed
(per cent of total)
|
| Midlands
| 244 (42)
| 985 (48)
|
| North
| 225 (38)
| 574 (28)
|
| South East
| 114 (20)
| 484 (23)
|
| South West
| 0
| 22 (1)
|
| Total
| 583 (100)
| 2,065 (100)
|
Source: National Audit Office
17. In 2001, the Agency had started to install cheaper,
less sophisticated technology in the South East in an attempt
to close the significant gap in technology provision between the
regions. It had planned to upgrade the technology at a later date.
Such an approach would, however, have cost £64 million
more than the progressive installation of more sophisticated technology
from the outset. The Agency had therefore decided to reverse its
earlier decision, and to implement the sophisticated technology
instead. The Agency had established a Technology Strategy Steering
Group to prioritise resources for technology projects nationally.[17]
14 Qq 33-34, 54-55 Back
15
C&AG's Report, paras 2.21-2.29 Back
16
Qq 10, 55, 57, 59; C&AG's Report, paras 3.7-3.13 Back
17
Q 9 Back
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