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Introduction
3.1 The way in which the motorway and trunk road network is managed, with the benefit of new technology and techniques and investment in modest improvements and capacity enhancements, can have a very major impact on the service provided to road users. It can also contribute to the achievement of integrated transport objectives. This chapter considers the range of tools which the Scottish Executive has at its disposal to effect major improvements in travel safety and the management and operation of the network without recourse to major road improvement schemes.
Making better use of the existing network
3.2 It is essential to ensure that the best possible use is made of the existing network and new opportunities are constantly arising with the development of technology. In recognition of the importance of this work, a Traffic Controller Unit was created in June 1999 within the Scottish Executive Trunk Roads Divisions. The prime objective of the new unit is to secure better use of the trunk road network. In addition, it provides a focal point for best practice in this area and a source of expertise which can be called upon by local authorities for use on their networks. The Traffic Controller Unit has already begun to implement a range of measures.
NADICS
3.3 The major tool which the Unit is using to manage the network is NADICS, Scotland's National Driver Information and Control System. This provides drivers on Scotland's trunk roads with up-to-the-minute information about road traffic conditions. From the National Network Control Centre in Glasgow, trunk road traffic conditions are monitored using close circuit television cameras and sensors either buried in the road surface or adjacent to the road. This is supplemented by information from Police control rooms, motorway emergency telephones, trunk road maintenance organisations and motoring organisations.
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NADICS control room |
Variable message sign on the A1 |
3.4 Traffic disruption is analysed either manually or automatically with the help of computerised systems. When the likely impact of any incident has been assessed, appropriate information is displayed on variable message signs (VMSs) located at strategic points on the network allowing travellers to consider alternative routes or alternative modes of transport.
3.5 The NADICS system is at the leading edge world-wide and will continue to be developed to give wider and better coverage to provide the traveller with relevant and timeous information. A web page giving constantly updated traffic data together with links to public transport and motoring organisations has just been launched. Coming on-stream in the near future is a system called Automatic Congestion Identification which will provide speedier responses on VMSs. Work is also ongoing to provide up to the minute travel time information on VMSs, giving drivers the estimated journey time to the next significant location.
Junction Stress Points
3.6 The Scottish Executive maintains the Scottish Road Traffic Database and carries out extensive traffic monitoring to keep the data up to date. Analysis of this comprehensive database allows junction stress points to be identified and analysed with a view to providing optimal low cost solutions to maximise capacity. Such solutions can include:
Park and Ride
3.7 The Traffic Controller Unit will offer assistance to Councils and others providing park and ride facilities, principally by offering drivers, via Variable Message Signs and the NADICS website, real-time information on traffic conditions on the route and the frequency of the bus/train services available.
Peak Hour Speed Limits
3.8 The Unit will investigate the use of advisory speed limits to control traffic speeds on the approach to congested areas at peak hours. By controlling the speed of vehicles and hence the numbers approaching congestion points to bring them into line with junction capacities, queuing is reduced and the throughput of the junctions increased.
Priority for buses/lorries/high occupancy cars
3.9 The Unit will examine, through research, the potential contribution, on appropriate sections of the network, of new traffic management measures such as priority systems or reserved space for particular categories of vehicles such as buses, lorries and high occupancy cars. This research will take account of experience elsewhere in the United Kingdom and further afield and the lessons we can learn from this.
Research & Development
3.10 The Unit will continue to undertake or sponsor other research projects, particularly in conjunction with European Partners, to ensure that Scotland remains at the forefront of developments in this field and to secure benefits at the earliest possible time. Ongoing or firmly planned research includes projects which will:
Minor improvement schemes
3.11 Modest investment can not only allow more efficient use of the existing network but also offers considerable scope for securing substantial improvements in the levels of service offered by trunk roads and in reducing their environmental impacts. This section explains the work undertaken to date and gives some indication of future developments.
3.12 Given Scotland's dependence on a network of predominantly long-distance single carriageway routes, Route Action Plans provide one of the most effective ways of targeting investment. With a Route Action Plan the route is examined in detail. First, its safety record is reviewed yard by yard to establish where accidents are happening, and then to identify the causes, whether they be related to site features of a particular location, or characteristics of the way in which drivers use the road. Where treatment can be provided by routine measures such as signing, road lining or surface anti-skidding improvement, this could be taken forward in a Route Accident Reduction Plan (see paragraphs 4.11 - 4.13 below). In other cases, the safety issues will be considered in the light of other conclusions arising from the Route Action Plan.
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Traffic calming on the A76 at Sanquhar |
3.13 Trunk roads pass through a number of communities where the construction of bypasses is not a practicable option for the foreseeable future. In these situations, traffic calming schemes can be incorporated into the Route Action Plan. A good example of this is the treatment to the towns along the A76, where action to improve traffic conditions in roadside communities was given early priority.
3.14 Although drivers on long distance single carriageway roads often experience "congested" driving as a result of long platoons of vehicles, the volumes of traffic on these roads are usually well below the ultimate capacity. A successful cost effective approach to such problems is to provide well placed and unambiguous overtaking opportunities where drivers can safely pass slower-moving vehicles. The Scottish Executive's computer simulation programme, REVS, allows the behaviour of drivers to be modelled along the length of the route and the effect of improvements, such as discrete sections of dual carriageway or climbing lanes, to be examined. In this way the optimum number of improvements, their type, and their location can be predetermined. Route Action Plan studies have already been completed on:
3.15 The Executive is also developing further innovative ways in which to use widened single carriageways to improve safety and overtaking opportunities. As part of the A68 Route Action Plan, designers have prepared an experimental scheme to provide mandatory priority for overtaking through a dedicated overtaking lane, alternating priorities between directions each one or two kilometres. To ensure that this operation works and also to improve safety, a new type of single carriageway layout has been developed. It is hoped that this will be implemented over the next 2 years.
3.16 The Route Action Plan principles have also been applied to the section of the A90 dual carriageway between Perth and Dundee where, in the face of road safety problems and traffic growth pressures, solutions were developed involving carriageway improvements and new flyover junctions.
3.17 Two further Route Action Plan studies are at present being finalised on the A75 between Gretna and Stranraer and on the A96 between Fochabers and Inverness Airport. In these 2 studies, consideration is being given to how public transport might contribute to integrated transport solutions.
3.18 The Scottish Executive plans to extend the coverage of Route Action Plans, where this can be justified, and to incorporate further public transport studies where this is appropriate. Increasingly, Route Action Plans will provide the framework for investment decisions relating to the routes covered. Route Action Plans could also have a useful part to play in the strategies emerging from wider, multi-modal corridor studies in which the opportunities to deliver modal shift can be examined (see para. 7.11 below). These could consider the most efficient use of trunk roads and investment in alternative or complementary modes (such as park and ride for bus and rail).
3.19 Significant improvements to traffic flow, with consequent time savings benefits to road users can also be secured, outwith Route Action Plan areas, at a relatively modest cost. This approach involves examining routes where congestion occurs, for example on the periphery of urban areas or on the Central Scotland inter-urban network. Using computer simulation, the geometry of junctions and links can be analysed to identify detailed features which reduce efficiency. This type of analysis has been used to refine the design of the complex link between the M9 at Newbridge and the M8. Here the interaction of traffic joining and leaving the motorway created the potential for congestion even within the new junction layout. The Executive will be developing this work and will consider funding solutions which clearly offer a high return.
Road Traffic Reduction Legislation
3.20 The Scottish Executive is also aware that the 2 UK Acts on road traffic reduction will have an important bearing on the use and management of the trunk road network and hence on the need for trunk road capacity enhancements. The Road Traffic Reduction Act 1997 requires local authorities to produce a report to assess existing levels of traffic on their roads, forecast expected growth in these levels and set targets for reducing levels of local road traffic, unless the authorities can justify that, for part or all of their area, this would be inappropriate. The Road Traffic Reduction (National Targets) Act 1998 requires Scottish Ministers to set a national target for road traffic reduction in Scotland and to publish this target in a report laid before the Scottish Parliament. Ministers are not required to set traffic reduction targets if they consider that other targets or other measures would be appropriate for the purpose of reducing the adverse impacts of road traffic. However, in reaching a decision on this matter, Ministers will be guided by the Executive's integrated transport strategy which recognises that the relentless growth in traffic evident over recent decades is simply unsustainable and that increased emphasis must be placed on alternatives to road transport, in general, and car use, in particular.
3.21 The Executive recognises that levels of traffic on the trunk road network will have an impact on local authority roads and that these levels can be affected by trunk road improvement schemes. In some circumstances, such schemes may attract traffic from local roads or, through a traffic generation effect, place additional traffic on them. Similarly, measures which local authorities propose to meet their Road Traffic Reduction Act obligations may have an impact on traffic volumes on trunk roads in or near their areas. Reflecting this, the Executive has been working with local authorities by providing them with available traffic modelling data to assist in their assessments of local traffic levels.
3.22 The Central Scotland Transport Model (CSTM3) covers 22 of the 32 local authority areas in Scotland (plus part of Perth & Kinross). We have supplied each of these councils with a standardised package of information as detailed below -
In addition, the following data were provided for the peak and off-peak travel periods and for a typical working day:
The focus of CSTM3 is on strategic movement by road and public transport with the emphasis on the trunk road network. The model has not been designed to, and therefore does not, consider the pedestrian or cycle element of a trip: this is more appropriately addressed in local models. However, these models are important given the preponderance of short trips in travel patterns and the potential they have to contribute as an element in more complex trips involving combinations of modes. Authorities will, therefore, be expected to take them into account in formulating their road traffic reduction and local transport strategies.
3.23 Of the 22 councils within the CSTM3 area, 2 (Clackmannanshire and Falkirk) used data from the model in their interim Road Traffic Reduction Act reports, submitted to the Scottish Executive in July 1999. A further 5 councils indicated that they will use CSTM3 information next year in compiling the statutory reports which they are required to submit by July 2000.
3.24 The Executive is also working in partnership with South Lanarkshire Council to collect traffic data, with the 3 Ayrshire Councils and the Strathclyde Passenger Transport Executive to collect public transport and traffic data and with the City of Edinburgh Council to collect public transport data.
3.25 The Executive is currently carrying out an analysis of the interim Road Traffic Reduction Reports submitted by authorities. This will assist in informing Ministers on how to proceed in meeting their obligations under the 1998 Act. The interim reports were submitted along with the draft Local Transport Strategies and, in considering these, the Executive will, itself, be looking at the linkages between the volumes of traffic on trunk roads and the strategies proposed by the authorities
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