Advanced motorway signalling and traffic management feasibility study (HTML version)
5 Potential Priority Locations for Roll Out
5.1 The greatest benefits can be derived from implementing advanced signalling and traffic management techniques on sections of motorway where traffic volumes and the associated congestion today warrant opening the hard shoulder as a running lane and controlled motorway operation. Accordingly, these locations will generate the highest returns on investment and deserve highest priority when considering further technology installation around the network. The question of whether other sections of motorway (with lower traffic volumes) might justify application of different elements of advanced signalling and traffic management technologies, but without the hard shoulder running facility, is considered later in this chapter of the report.
Where would hard shoulder running be beneficial?
5.2 Following the successful M42 pilot, the Highways Agency has been developing proposals to extend hard shoulder running to the motorway box around Birmingham, the next phase of which was announced by the Secretary of State for Transport in October 2007. It has also been looking at the potential for hard shoulder running as an alternative to some planned widening schemes for the M1 (Contract 2 of the J21-J30 scheme, and between J30 and 42), the M62 (J25-J28) and sections of the M6 (J11a to 19). These are detailed studies which are ongoing.
5.3 For this feasibility study we have adopted a strategic approach to identifying the future potential for hard shoulder running across the motorway network. Since the benefits of using the hard shoulder as a running lane derive from improved service levels at congested times, we have focussed on parts of the network where future traffic flows per lane and congestion are expected to be greatest.
5.4 Some sections of the motorway network already have four running lanes, and in other locations, widening schemes are under construction or at an advanced stage of planning or procurement (four sections of the M25 and M1 junctions 10 to 13). These were excluded from the scope of this study, together with sections on which hard shoulder running is already operating or committed.
5.5 Based on the results of the M42 pilot, we identified a threshold flow volume, above which traffic conditions would justify bringing the hard shoulder into operation. This threshold was set at flows of 1,500 vehicles per lane per hour (4,500 vehicles per hour across a three lane carriageway). This would typically imply speeds of around 60mph or below, owing to the level of traffic congestion.
5.6 For the motorway network within the study scope, we examined forecast flows up to 2014 for each 'link' - or section between junctions - against the threshold flow. Using a spreadsheet model, we identified the first year in which the hard shoulder would be brought into operation (from 2010, the earliest feasible delivery year), and the number of hours it would operate.
5.7 For each link we calculated an indicative benefit cost ratio (BCR) over 30 years, assuming an implementation year of 2010 and hard shoulder running at 60mph. We used an initial basic cost estimate for installing the infrastructure of £3m per kilometre, based on work done by the Highways Agency to refine the basic design assumptions for hard shoulder running schemes in light of the experience of the M42 scheme. (Subsequent work suggested a rather higher cost, of around £4m per km, to which a risk adjustment was applied - an additional 40%. This higher figure was used in assessing the overall business case as discussed in chapter 6, but it would not affect the ranking of potential sites for the application of hard shoulder running.)
Priorities for the short to medium term
5.8 Using the methodology described above we identified links where flows would be sufficient to justify use of the hard shoulder for some part of the day before 2015. Those with an indicative BCR of at least 2.5 were identified and contiguous links were grouped into schemes.
5.9 This analysis identified the following priority sites for hard shoulder running for the medium term as shown in red on figure 8 below. There may also be a case for including additional links to provide more continuity and consistency of service to the road user. The priority sites identified are based on a high level analysis, as noted earlier. A full business case assessment for each potential site has not been possible in the timeframe of this study.
Figure 8: Potential managed motorway network
5.10 The schemes shown in figure 8 add up in total to approximately 400km of motorway route (carriageways in both directions) and a further 17km in one direction only.
5.11 Benefits included in the indicative BCR were changes to speeds and delays from queuing and merging and changes to vehicle operating costs (mainly fuel). The indicative BCR does not take into account savings in accidents, changes in carbon and emissions outputs, or network effects (such as the effects on other roads). However, we believe that the analysis is robust in developing priorities. Accordingly, these schemes have been used as the basis of the business case assessment for rolling out hard shoulder running, at a programme level, including an assessment of the savings in accidents, changes in emissions outputs and network effects (such as the effects on other roads). The results of this business case development work are detailed in chapter 6.
The longer term potential
5.12 If hard shoulder running was introduced on the links identified in figure 9, then a number of the gaps would exist between sections of hard shoulder running. To enable us to look further ahead, we have carried out a similar assessment looking to the need for hard shoulder running up to 2024. This would fill some of the gaps and extend some of the identified schemes, in all adding a further 73km of route (both directions).
Locations for Controlled Motorway
5.13 Controlled Motorway operation is currently in use on the western quadrant of the M25. We have examined where on the network investment in CM might be justified, based on the significant safety benefits derived on the M25 scheme. Where there are high traffic flows CM is also expected to have a beneficial impact on journey time reliability. Drawing on the before and after analysis of the extension of CM from Junction 15 to Junction 16 of the M25, the Highways Agency has developed an assessment tool to indicate where there could be a case for installing full CM on a three lane motorway. This compares the forecast flows and accident rates at which CM would be expected to give benefit cost ratios of the order of 2.0 to 3.0, depending on traffic flows.
5.14 The national average accident rate for all motorways is 8.9 personal injury accidents per 100 million vehicle km (2004 to 2006 average). This would justify CM only at the highest levels of flow. At low flows, when there would be less scope for accident reduction, CM would only be viable in conventional business case terms where the accident rate is well above average.
5.15 Figure 8 shows in royal blue the additional motorway sections which we have identified as appearing to justify investment in CM. They are the M1 junctions 39 to 40 southbound, the M6 junction 20 to 21 and M4 junctions 8 to 10 in both directions. Overall, this amounts to 16.2 route km in both directions and an additional 4.2km in one direction only, at a roughly estimated cost of between £18.3m and £27.5m (for CM at between £1m and £1.5m per km).
5.16 There is also a case for exploring whether there are viable investment opportunities, at lower cost, to manage traffic flows more effectively during seasonal peaks, on motorway routes where these are significant. In the timescale of this study we have not been able to investigate this.
Continuity of provision
5.17 Our link by link approach to identifying where hard shoulder running or CM would provide the greatest quantifiable return produces a picture where some motorways would justify hard shoulder running over a significant proportion of their length. Although the M42 pilot has shown that it is feasible to provide a discrete section of hard shoulder running, in these cases there are likely to be benefits in taking a more strategic approach to the whole motorway or long sections of it, providing at least some of the elements of the managed motorway in the 'gaps' even where they are not justified on a stand alone basis. This would deliver a more consistent driving experience, minimising the scope for confusion; and more consistent provision of signs and information would increase opportunities for strategic management of the motorway as a whole.
5.18 We have considered this issue especially in relation to the motorway links between London, Birmingham, Manchester and Leeds, where there are relatively small gaps, and therefore a good case for some infilling. MIDAS already exists or is being installed on all stretches of this network where our analysis left gaps (except M1 J10 - J13 where provision of MIDAS is planned with the current improvement scheme). All the gaps also have CCTV except M1 J35a - J39. The main options for further filling the gaps are:
- upgrading to Basic Controlled Motorway. This would provide some visual continuity of portal gantries - though at entry to links only. In addition it would provide a capability to apply mandatory speed limits, which would deliver some safety benefits (but less than full CM). It would not allow for full dynamic management of traffic, because of the less frequent spacing of the gantries. We estimate this would cost around £0.25m per km, or approximately £40m to fill all the gaps.
- upgrade to Controlled Motorway. This would have the advantage of providing visual continuity of portal gantries, and capability to use mandatory speed limits flexibly (delivering the full CM safety benefits) and to actively manage traffic. However it would cost more, at about £1.0m-£1.5m/km, or approximately £200m to fill all the gaps.
Further consideration would need to be given to the business case for these options, reflecting the available budget and the strategic considerations noted above.
5.19 The pace and priority of the roll out of hard shoulder running and other managed motorway interventions will depend on several factors, some scheme related and some common across the programme - not least the available budget and the need to take account of various needs and pressures across the whole Highways Agency road network. However, hard shoulder running should prove to be a quicker way to alleviate congestion problems on the network than conventional widening. Less work will be necessary to deliver hard shoulder running and it is more likely that such schemes will be delivered within the highway boundary, obviating the need for statutory land acquisition procedures. Experience from the M42 pilot suggests that hard shoulder running can also be delivered with a smaller environmental footprint than widening.
5.20 The work involved in delivering a particular scheme will depend on local network conditions. Where the existing carriageway construction is sound and there is a continuous full width hard shoulder, installation of the infrastructure could probably be managed with little disruption to traffic. Most of the work could be carried out outside peak hours and accessed from the hard shoulder and the verge beyond. However, if carriageway reconstruction is needed or works to provide a full width hard shoulder are necessary (such as bridge widening), or if it is decided to include other safety related features such as a concrete central reserve barrier, then more intrusive traffic management would be needed to safely manage the work and to safeguard road workers. Where the network is carried on structures over long lengths (such as the M6 between J6 and J8) consideration will need to be given to the works required to up-grade and/or strengthen these structures in deciding their place in the roll out programme.
5.21 Where works that interfere with traffic flow are necessary, these would need to be coordinated with other works on adjacent sections of the network. This would have to be considered in scheduling works to minimise the impact on motorists. The roll out would also have to be planned to ensure that we achieve best value for money, through such initiatives as early engagement with the supply chain and the bulk purchase of equipment. Further work will be done by the Highways Agency to maximise the opportunities for reducing the construction impact and to derive maximum value for money.
5.22 The priorities for roll out will also be dependent on the further analysis that will be carried out to ensure that cost estimates and benefits reflect local network and operational conditions. Given that there will always be pressure to do more than we have resources to deliver, the scheduling of scheme implementation would depend in part on the business case benefits and on the need to schedule the roll out to maximise the network benefits arising from providing motorists with a consistent driving environment (noted above).
5.23 Several of the stakeholders represented in our advisory group were concerned that implementing hard shoulder running schemes in particular locations might lead to increased pressure on local roads. Clearly, thorough analysis of the impact of a hard shoulder running, or any other managed motorway scheme, on local roads would need to be carried out before implementation, and mitigating measures built in to schemes where necessary, such as the range of Integrated Demand Management measures being developed by the Highways Agency and local authorities in association with the M25 widening.
Summary of conclusions
5.24 To summarise:
- Our high level analysis indicates that there are a number of sections of the motorway network that would benefit from dynamic use of the hard shoulder at congested times in the short to medium term (initially to 2014), to deliver congestion benefits where most urgently needed.
- The priority locations we have identified include most of the sections of the M1, M6 and M62 where there are planned widening schemes but also some locations where there are no planned widening schemes, such as the M27 around Southampton, the M4/M5 at Bristol and the radial routes around the M25.
- Other traffic management interventions without the hard shoulder running facility may also be desirable on other stretches, both in traffic terms and in order to create a coherent 'managed motorway' network proposition.