Highways plans and strategies

The importance of establishing and practising a sound approach to asset management is recognised by the Department for Transport.

The Highway Maintenance Efficiency Programme was established to assist local authorities with managing assets. More recently future highways funding allocations will reflect how well a local authority practices asset management.

The Highway Asset Management Policy and Strategy document is supplemented by other key documents including the Highway Network Management Plan and the Northamptonshire Transport Plan.

Highways Asset Management Policy - January 2025

1. North Northamptonshire Council (NNC) recognises the important role of North Northamptonshire’s local road network in supporting the authority’s vision and strategic goals.
2. The council is committed to making the best use of its budgets and supports using an asset management methodology as a primary driver for maintaining the local highway network. This approach will ensure the best long-term results for local communities, by helping deliver the best value highway services.
3. This policy links NNC’s Highways Asset Management approach to wider transport and corporate plans and strategies, and supports the overarching vision that ‘North Northamptonshire be a place where everyone has the best opportunities and quality of life’.
4. This Highways Asset Management Policy has been developed with an associated Highway Asset Management Strategy to ensure that the principles of asset management are embedded in the delivery of NNC’s highway management and maintenance services. Implementing a highway asset management approach will help the council to understand the assets it is responsible for, measure and monitor how they perform, and determine the funding required to manage and maintain them in the future, to ensure safety, serviceability, sustainability and value for money. The contribution of the Asset Management Strategy to the six key supporting corporate commitments is briefly set out below.

Active, fulfilled lives

The accessibility provided by a well managed and maintained highway network is fundamental to achieving these priorities.

Better, brighter futures

The highways network is one of NNC’s principal assets and requires significant resources for its management and maintenance. This provides opportunities for employment, training and development directly at NNC and through our supply chain.

Safe and thriving places

The provision of tangible transport options to satisfy individual and corporate needs is essential to support NNC’s aspiration to make North Northamptonshire the great place to live and work and do business. The overall transport system needs to be able to provide fast and efficient movement of people and goods and an effective and efficiently managed and maintained highway network is the major component of that system.

Green, sustainable environment

Asset management supports the delivery of a well-maintained highway network in which planned and preventative maintenance are prioritised to ensure the lifecycles of assets are maximised. In addition, the use of using of recycled and innovative materials and methodology within maintenance programmes can play a crucial role in helping develop a sustainable transport system and network

Connected communities

The highway network is the significant component of the connectivity required by the residents and communities of North Northamptonshire, which also promotes and enables recreational and other activities including those in the voluntary sector.

Modern public services

The highway network serves the residents of North Northamptonshire, as well as its visitors. It also provides infrastructure to support the growth of the North Northamptonshire’s economy. Effective and efficient management of the highways network is a key factor in the ability of the council to deliver its services and enable the economy of North Northamptonshire to thrive.

Highway Asset Management Strategy - January 2025

1.0 Introduction and Policy

1.1 North Northamptonshire Council (NNC) is responsible for maintaining a highways network that not only serves the residents of NNC but also supports the growth of the North Northamptonshire economy and promotes recreational and other activities. Effective and efficient management of the highways network is a key factor in the ability of the council to deliver its services and enable the economy of North Northamptonshire to thrive.

1.2 Effective asset management is one of the key factors in delivering a highway network that meets North Northamptonshire’s needs. Asset management will allow decisions to be made in a consistent manner and will allow the highway assets to be managed and maintained appropriately to ensure safety, serviceability and sustainability, as outlined in NNC’s Highways Asset Management Policy.

1.3 The policy states that NNC will manage and maintain its highways assets in a planned, cost effective, coordinated, sustainable and efficient manner, over the whole life cycle of the asset.

1.4 The Asset Management approach follows best practice and incorporates guidance given in the UK Roads Liaison Group/Highway Maintenance Efficiency Programme (UKRLG/HMEP), Highway Infrastructure Asset Management Guidance Document, along with processes and procedures that are consistent with the requirements of BS ISO 55001:2014.

1.5 This Highways Asset Management Strategy (HAMS) is designed to set out NNC’s long term direction for the management of the council’s highways assets and application of the Highways Asset Management Policy. This document also includes the Highways Asset Management Objectives.

1.6 The strategy will be achieved by adopting plans and processes that will:

• adopt a life-cycle approach to planning asset investment and management decisions
• balance competing needs across the highway network and selecting options that best meet desired outcomes and stakeholder requirements
• comply with mandatory, statutory and regulatory requirements
• monitor, evaluate and, where required, improve service delivery
• manage the risks of asset stewardship and operation to ensure continuity of service
• provide for present needs whilst sustaining natural resources for future generations
• adopt a continuous improvement approach to asset management practices and performance
• empower and motivate the workforce involved in the operation and maintenance of the network
• outline maintenance regimes for each asset group that seeks to deliver value for money by prioritising works according to need and using cost effective maintenance techniques

1.7 Effective Asset Management is one of the key factors in delivering a highway network that meets North Northamptonshire’s needs. It will ensure decisions are made in a consistent manner and allow the highway network assets to be managed and maintained appropriately to ensure safety, serviceability and sustainability.

2.0 Relationship between Policy, Strategy, Objectives and Asset Management Plans

2.1 This document is a link between the Highways Asset Management Policy at a high level and the Highway Asset Management Plans at an implementation level. It sets out NNC’s strategy and objectives for the management of NNC’s highways assets.

2.2 The “line of sight” between organisational strategic direction and the day-to-day activities of managing assets is a vital component of the asset management system. This aligns the “top down” aspirations of the organisation with the “bottom up” realities and opportunities of the assets.

2.3 Highway Asset Management Framework

Flowchart

3.0 The NNC Highways Asset

3.1 Asset Portfolio

3.1.1 This Highway Asset Management Strategy applies to all NNC’s highways assets. All of these assets are managed in accordance with the recommendations contained within UK Roads Liaison Groups (UKRLG) Well Managed Highway Infrastructure - A Code of Practice.

3.1.2 Key assets include carriageways and paved areas, footways and cycleways, structures, drainage, street lighting, and traffic signals and associated technology. Wider highway assets include boundary fences, geotechnical assets, road markings and road studs, vehicle restraint systems, road traffic signs and environmental and soft estate assets (verges, grassed areas, trees, central reservations, amenity areas, cultural heritage assets and hard landscaping assets).

3.1.3 For the purpose of this strategy Public Rights of Way (PROW’s) are not included. PROW’s are managed through the council’s Right of Way Improvement Plan (ROWIP).

3.2 Asset Management assessment

3.2.1 Each main asset group asset is managed using asset management principles and intelligence based decision making (where possible) using a multicriteria analysis tool HEAT (Holistic Evaluation and Assessment Tool).

3.2.2 HEAT is a decision support tool that has been developed to assist in the prioritisation of capital maintenance schemes. HEAT ranks asset needs and schemes using weighted prioritisation factors across several different categories to come up with a multi-criteria prioritisation decision.

3.2.3 The following categories and factors are used for HEAT prioritisation:

a) Asset Condition - physical condition, safety, history of emergency interventions.
b) Network Impact - traffic volumes and category of route, facility accessed (school, hospital, etc.), location (urban or rural), criticality (availability of alternative routes).
c) Efficiency - ability to combine with other schemes, impact on life extension, preventive maintenance.
d) External - social value (deprived area status), stakeholder and customer complaints and claims.
e) Sustainability - not included at this time but planning to allow for environment and ecology impact and carbon footprint.

3.2.4 HEAT is currently being used for carriageways, footways and bridges and structures scheme prioritisation and it is intended that this will be extended across all highway assets during 2025.

3.2.5 Details of the HEAT approach for each main asset group will be included in Asset management plans that will be produced for individual asset group and groups of assets. This will detail how the strategic priorities are delivered on an individual asset basis. This process provides the source information used to develop schemes for inclusion in the council’s Highways Annual Plan. Furthermore, this ensures the high level optimisation and prioritisation of schemes and embedment of the overarching concept of ‘Prevention is better than cure’ and the ‘right first time’ approach.

3.2.6 The role of local members to challenge forward plans is vital to ensuring that local priorities are incorporated into the council’s Annual Plans, whilst also taking into account asset condition as well as current and future levels of funding. Changes to planned funding levels may impact the desired asset management approach and re-modelling and evaluation will take place accordingly.

3.3 Critical Assets

3.3.1 Critical assets are defined on an asset by asset basis dependent upon their location, condition and the impact any failure would have on the safe and smooth operation of NNC’s highways network. Those that are critical will be identified and the risks associated with each asset will be addressed within the relevant asset management plan. This will include identification of factors that will influence non-performance and the impact of failure. Those factors will include:

• Location
• Technical requirements for the asset
• Failure mechanisms
• How the asset becomes critical

The consequence of failure of such assets will be high although they may not necessarily have a high likelihood of failure.

3.4 Consequence of Failure

3.4.1 Where critical and other assets may be subject to sudden failure, measures will be put in place as soon as practicable to ensure the safety of road users and to limit further deterioration of the asset. This may include closures, temporary works and provisions and implementation of diversionary routes.

3.4.2 In the event of a sudden asset failure, Annual plans will be reviewed, re-prioritised and amended to ensure sufficient funds are made available for the required repairs and renewal.

3.5 Desired Future State

3.5.1 NNC is committed to maintaining a highway network that is safe and serviceable to current levels, as well as carry out vital renewal work to help keep journeys safe and reliable to meet the council’s vision and priorities. It is also committed to sustaining that network over the medium and longer term. It is recognised that limitations on funding may restrict maintenance spending from time to time and in such situations the network will need to be closely managed to maintain safety and availability.

3.5.2 Detail on current condition and desired future state for individual assets will be provided in the asset specific asset management plans.

4.0 Asset Management

4.1 The application of asset management principles is a fundamental element of this Highway Asset Management Strategy.

4.2 Asset management is a modern but well-developed discipline that is practised in many countries and across a wide range of industries. It is applied to the whole life of assets and determines the optimum way of managing them to achieve the desired outcomes. The stages of an asset’s life covered by asset management are illustrated below:

4.3 The “operate, maintain & improve” phase is the core area for the management of highway infrastructure assets in NNC, but new and additional infrastructure will be introduced as the need rises and redundant infrastructure will also be removed where no longer required.

4.4 There are a wide range of recognised definitions for asset management, all of which align with a core set of principles. The definition of Asset Management in standard BS ISO 55001:2014 is:
“coordinated activities of an organisation to realise value from assets”

4.5 Within NNC, there are additional requirements and pressures which drive the approach to asset management, for example, our service providers and supply chain and maintaining a balance of work across the wider portfolio of assets. These external influences mean that asset management principles are applied discretely for each asset type and that a fully co-ordinated approach cannot always be demonstrated. However, hybrid schemes and efficiencies in use of road space are sought where possible to reduce impact on road users.

5.0 Drivers for Asset Management

5.1 Changes in Investment Levels

5.1.1 The improved awareness and knowledge of the highway assets and their current condition and needs that arise from the application of asset management principles, will allow NNC to be positioned to act quickly should opportunities arise for additional funding. The council is proactive in submitting business cases to the Department for Transport (DfT) to support such additional funding and it is anticipated that such funding will be forthcoming in the future.

5.1.2 NNC will work cooperatively with its service providers and their supply chain to ensure that the available budget is spent wisely and delivered efficiently through the development of asset specific asset management plans.

5.2 Management of Service Providers and Supply Chain

5.2.1 The application of asset management principles and the collaborative working practices embodied in such principles will encourage the ‘working with’ rather than ‘working for’ culture necessary to be able to act quickly to address any changes, risks and opportunities arising. This will provide frameworks to encourage the early contractor involvement necessary to facilitate effective planning and programming, as well as timely decision making.

5.3 Life Cycle and Risk Management

5.3.1 NNC understands that the way it manages and maintains the highways assets today will have impacts on the way they will have to be managed and maintained in the future.

1. Identification and feasibility
2. Planning and design
3. Construction
4. Operate, maintain and improve
5. Disposal

5.3.2 Life cycle planning comprises the approach to the maintenance of an asset from construction, operation and maintenance to end-of-life disposal. The operation and maintenance phases are the core areas for NNC. Life cycle planning will support levels of funding and investment decisions and substantiate the need for appropriate and sustainable long-term funding.

5.3.3 One to three year programmes of maintenance and renewal schemes will be prepared in conjunction with NNC’s service providers and supply chain and populated with schemes developed and prioritised on the basis of asset need determined from the condition of the assets, network impact, customer and sustainability factors.

5.3.4 Funding is allocated across different asset groups giving consideration to the above factors but more directly to impact on the safety of the travelling public and the integrity of the network in an environment where funding may be constrained.

5.3.5 NNC understands that the way it carries out repairs and maintenance to assets has an effect on their ultimate service life and advocates a right first time approach. NNC will always look to optimise this relationship and avoid short term repairs and treatments that would only defer problems. Whole life cost analyses will be used when making engineering decisions for repair and treatment options.

5.3.6 The benefits of a systematic approach to managing current and future risk at strategic, tactical and operational levels are recognised. Risk management will be a fundamental component of NNC’s management system for its assets.

6.0 Asset Management Objectives

The Asset Management objectives provide the specific and measurable outcome or achievement required to implement the Highway Asset Management Policy and this Highway Asset Management Strategy.

6.1 Factors Influencing Objectives

The Highway Asset Management Objectives derive from the following sources:

• Vision, Priorities and Objectives of NNC
• The Highway Asset Management Policy and this Highway Asset Management Strategy
• The requirements of BSI ISO 55001:2014
• Commercial requirements
• The mechanism of delivery of management of the various assets

6.1.1 NNC will establish and will maintain asset management objectives, which:

a) Are measurable (i.e. quantified and/or capable of being demonstrated as achieved through objective assessment)
b) Are derived from, and consistent with, the asset management strategy
c) Are consistent with NNC’s commitment to continual improvement
d) Are communicated to all relevant stakeholders, including contracted service providers, where there is a requirement that these persons are made aware of their obligations
e) Are reviewed and updated periodically to ensure that they remain relevant and consistent with the asset management strategy
f) Consider legal, regulatory, statutory and other asset management requirements
g) Take account of the expectations of relevant stakeholders and financial, operational and business requirements
h) Take account of asset management related risks
i) Consider improvement opportunities including new technologies and asset management tools, techniques and practices

6.2 Objectives

6.2.1 NNC’s priorities are incorporated within the asset management objectives under six headings as follows:

1. Planning for the Future
a) Improve the quality of asset data collection and provide systems which allow data to be easily interrogated and interpreted to identify asset needs and opportunities.
b) Make full use of asset data when making asset investment decisions.
c) Individual asset leads to acknowledge the need to take a long-term view of their assets and work towards. implementation of a Lifecycle Asset Management Plan (10-year plus).

2. Growing our Capability
a) NNC will maintain processes and procedures that are consistent with ISO 55001:2014.
b) NNC and its service providers will maintain the operational training levels of its teams to deliver their roles in a safe and competent manner.

3. Building Stronger Relationships
a) NNC will work closely with other agencies operating in North Northamptonshire to offer a joined up approach to the delivery and support of renewal and other projects.
b) NNC will extend opportunities for asset management training and guidance to its collaborative delivery partners.
c) NNC will work collaboratively across disciplines to optimise network occupancy.
d) NNC will communicate work programmes to key stakeholders.

4. Efficient and Effective Delivery
a) NNC will actively seek opportunities to share road space.
b) NNC will encourage innovation, bringing new materials, plant, techniques and practices into use.
c) NNC will make asset led decisions to ensure that the available funding for each asset type is spent in the most effective way as outlined in each asset specific asset management plan.
d) NNC will work with its service delivery partners to ensure work is planned effectively and productivity is maximised.

5. Improving Customer Service
a) NNC will engage with stakeholders to improve the overall understanding of its highway maintenance activities, programmes and priorities, and the accessibility of information.
b) NNC will introduce a priority rating for enquiries which drive an improvement in timeliness of responses.

6. Health, Safety & Environment
a) NNC will facilitate road safety audits for all new designs and improvements.
b) NNC will identify and implement environmental and carbon initiatives.
c) NNC and its service provider will include asset management related competencies within its competency framework and role descriptions.

6.2.2 The individual highway asset management plans will develop these objectives into specific deliverables and a plan that is relevant to the levels of service and the condition, nature and needs of each highway asset.

6.3 Desired Asset Condition and Outcomes

6.3.1 Effective maintenance and operation of the NNC Highway Network is essential in achieving the Asset management objectives.

6.3.2 The various assets comprising the NNC Highway Network have different design lives and maintenance and renewal intervals. A common desired condition or outcome cannot, therefore, be defined.

6.3.3 Desired future asset condition and outcomes for individual assets are outlined as follow:

*Street Lighting is managed through a PFI Contract with Balfour Beatty which started in 2011 and runs to 2036

6.3.4 The individual Highway Asset Management Plans will define the desired condition, outcomes and maintenance requirements of each asset in detail. However, the over-arching requirement is that the assets are assessed and maintained to remain in a condition where they support the safe operation and availability of the road network and other associated assets. This goal is achieved by planned regular inspection, and consequent repairs and maintenance works programmes.

6.3.5 The aspiration is not to achieve a defect-free asset, but one where defects that affect safety and serviceability are addressed.

7.0 Stakeholders

7.1 There are many stakeholders that may be affected or have an impact upon management of the highway asset. The requirements and expectations of each of these may be the same - a safe, serviceable and sustainable network. It is the prioritisation they each give to these outcomes that differ.

7.2 NNC will ensure that relevant information associated with asset management activities (i.e. schemes or maintenance activities) will be actively communicated through engagement with relevant stakeholders. A Customer and Stakeholder Engagement Plan will be maintained to ensure effective communication with stakeholders.

7.3 Key stakeholders include NNC Members, Parish and Town Councils, NNC Highways Staff, Kier Highways Asset Management Team, Kier Highways Operational Teams, NNC SLT, members of the public, utility companies, local businesses and community organisations.

7.4 To help support the needs of local communities, the council is open to exploring opportunities to work with Parish and Town Councils that may allow them to help support the delivery of appropriate highway maintenance activities at a local level.

8.0 Highway Asset Management Plans

8.1 This strategy will be delivered through specific Highway Asset Management Plans (HAMP’s) for each key asset group. These plans will contain the specific requirements for the desired future state of each asset with due reference to deterioration mechanisms, network resilience and critical assets.

Each HAMP will address the following criteria:

• A - Definition of the Asset
• C - The current Condition of that asset and procedures for inspecting the condition
• M - Risk-based and value management-based proposals for Maintenance of that asset
• I - Risk-based and value management-based proposals for Improvement of that asset

8.2 Each HAMP will also include a section on the visions and goals for that asset as well as information on the desired future state, the condition for that asset, and service standards and repair interventions.

8.3 The HAMP’s will be simple operational documents containing essential information that will help asset managers and operational delivery teams manage those assets.

9.0 Optimisation and Prioritisation

9.1 NNC’s approach to managing and maintaining the North Northamptonshire highway assets will be holistic and end-to-end. That is, NNC will always consider how the repair and maintenance of one particular asset or asset group impacts on other assets.

9.2 Forward programme meetings will be held and attended by individual asset managers, delivery managers and budget holders, to agree and coordinate plans for future maintenance schemes. A 3 year rolling Annual Plan will be developed each year, containing planned funding across all asset groups. The first year of the programme is approved for schemes in the following financial year (April to March) in February of each year.

10.0 Communication

10.1 A Customer and Stakeholder engagement plan will be developed to ensure all issues relevant to Highways Asset Management including this strategy are communicated to all relevant stakeholders. This plan will also outline the mechanisms by which the service engages with its parish/ town councils, its wider customer base and local members, around highway maintenance activities.

11.0 Performance and Improvement

11.1 The Highway Asset Management Policy and Strategy will be reviewed annually, once yearly condition survey results have been collated. Asset management performance against the highway asset management strategy will be assessed against the desired outcomes outlined for each asset in section 6.3 as detailed in the Asset management plans.

11.2 Following review, changes will be made to the strategy and if necessary the highway asset management plans, to address any shortcomings in terms of the performance and effectiveness of the approach taken. By reviewing the Strategy, the council will be able to make informed decisions to accommodate any changes in funding and priorities within the longer term forecasts.

11.3 An Asset Management Improvement Plan will be developed to help support the continuous improvement of NNC’s Highway Asset Management practices. This will include analysis of the quality of asset data and the way it is collected, along with consideration for the incorporation of new and emerging technologies where appropriate.

11.4 Opportunities will be sought to benchmark performance against that of adjacent authorities.

12.0 Competencies and Training

12.1 NNC considers the competency and motivation of all involved in the delivery of asset management related duties to be essential, be they directly employed by NNC, service providers or by supply chain partners. Asset management competencies will be included within NNC’s competency framework and training will be provided where necessary.

13.0 Good Practice

13.1 North Northamptonshire Council is committed to developing and implementing best practice and will make best use of the following forums where appropriate:

• Highway Maintenance Efficiency Programme (HMEP)
• The Chartered Institute of Public Finance and Accountancy (CIPFA)
• Highways Asset Management Planning Network
• Highways Asset Management Financial Information Group (HAMFIG)
• UK Roads Board
• Midlands Highways Alliance (MHA)
• ADEPT Asset Management Working Group
• Cross Contract collaboration and sharing of best practice
• National and regional conferences
• Professional Institution engagement
• Competency training

By building a publicly accessible network of on-street EV charging points, we aim to facilitate the uptake of EVs and achieve our broader Net Zero targets.

The strategy addresses the need for convenient charging solutions - particularly for residents without driveways. It also supports the transition of other transport forms to zero emissions including:

• buses
• private hire vehicles
• business fleets

LCWIPs provide:

• network plans for walking and cycling (which identify preferred routes and core areas for future development)
• prioritised future improvements that we can invest in
• technical report setting out the underlying analysis and why improvements are needed

Although LCWIPs aren't compulsory, the Department for Transport advised that councils who have plans will be well placed to make the case for future investment. They also confirmed that any funding bids need to meet the design standards outlined in their latest cycling guidance.

Our LCWIPs

Kettering LCWIP

The walking improvements identified are based upon a Core Walking Zone of the town centre area and 5 specific walking routes:

• Rockingham Road
• Lower Street / Rothwell Road
• Montagu Street / Stamford Road
• London Road
• Station Road

The cycling improvements consist of the following 14 routes:

• Barton Seagrave
• Burton Latimer
• London Road
• Northampton Road / Lake Avenue
• Northfield Avenue
• Pytchley Road
• Rockingham Road
• Rothwell Road
• Stamford Road / Weekley
• Station Road
• St Mary’s Road / Deeble Road
• Town centre
• Wicksteed Park
• Windmill Avenue

The Kettering LCWIP was approved by the North Northamptonshire Council Executive Committee in September 2023.

Corby LCWIP

The cycling improvements identified primary and secondary cycle proposals. The 7 primary cycle corridors are:

• Station Link
• Eastern Corridor - A427 Weldon Road between the railway station and eastern parts of the town, including Weldon and Priors Hall Park
• Northern Corridor - George St-Cottingham Rd, Studfall Avenue-Clydesdale Rd, Studfall Avenue-Rockingham Rd, Rockingham Rd and Rockingham Castle
• North Eastern Corridor - Old Village, retail off Phoenix Parkway, large employment sites off Steel Road and Priors Hall Park
• South Eastern Corridor – Little Stanion, Stanion and Magna Park
• South Western Corridor - Oakley Road between the town centre and residential areas
• Western Corridor - A427 Westcott Way and Cottingham Road, Cottingham, Middleton

The walking improvements identified are based upon:

• a Core Walking Zone of the town centre area and 11 walking routes
• an area based approach in Corby Old Village
• most of the recommended walking improvements align with the identified primary cycle corridors - the links which do not align are Corporation Street (CWZ2 & CWZ3), Richmond Road (CWZ 7) and High Street in Corby Old Village (W8, W9 and W10)

The Corby LCWIP was approved by the North Northamptonshire Council Executive Committee in January 2024.

Wellingborough and Rushden Area LCWIP

This LCWIP is currently under preparation and is programmed to be completed during 2024.

Production of a Local Transport Plan is a statutory requirement of the Transport Act 2000 and Local Transport Act 2008 which requires us to set out our plans and policies for transport as well as how we intend to implement them.

Thematic transport strategies

Town transport strategies

The objectives, policies and standards required to effectively deliver services and manage the area's highway network are detailed in the Network Management Plan.

The parking standards outlined in this document are set as a minimum, so encouraging well-designed parking as part of the development. The document also sets new dimensions for parking spaces as vehicles have become larger.

As well as a detailed action plan, the document explains how public rights of way and access routes fit in with other important strategies such as the local transport plan, growth strategies, the healthy lifestyle agenda and agri-environment schemes.

It is a full 4-stage transport model covering:

• trip generation
• mode choice
• trip distribution
• assignment

The demand model (trip generation/mode choice/trip distribution) and the public transport model are created using EMME3 software. The highway model is created using a suite of software called SATURN (Simulation and Assignment of Traffic to Urban Road Networks) originally developed by the University of Leeds and since marketed and developed in association with Atkins.

The model:

• is created in accordance with guidance issued by the Department for Transport
• covers the whole of the county, with an increasingly less detailed coverage beyond the county borders

The basis of the model is a combination of Roadside Interview Surveys (being replaced in the current model update by mobile phone data) and traffic and bus or rail passenger counts. As the survey information cannot represent all trips, data from the census and National Travel Survey is used to infill the missing trips, so that the model should represent all trips beyond very short journeys in Northamptonshire. This model is known as the ‘base year’ model.

These trips are represented in the model in a matrix of movements between zones. The zones vary from quite small areas near town centres to some very large areas well away from the county.

The public transport model represents the various bus and rail routes which exist in the county, together with information on their frequency.

The highway model has a simplified computer model of the county’s road network, and of key routes to destinations further afield. The network does not include every single residential or minor rural road, but is sufficiently detailed for trip patterns to be modelled.

Each link in the network has a length and a free-flow speed, together with an equation by which speed reduces as traffic flow increases. In addition, in the more detailed areas of model coverage there are simplified junction models of the roundabout, traffic signals or give-way as appropriate to allow the delay at those junctions to be modelled.

The trips from the matrix are ‘assigned’ to the network. On each ‘run’ the model looks for best route between two points. This routeing is determined from something known as generalised cost, which is a combination of time and distance. As the route choice varies as flow increases, the model runs dozens of iterations until a degree of stability in the assignment is found. It then applies information from the last few model runs so that vehicles travelling between A and B can follow a number of different routes, representing the different choices people make.

An independent set of traffic counts (known as validation data) which has not been used in the production of the trip data is used to check that the base year assignment model is representing things correctly. There is a series of statistical tests set by the Department for Transport which the model is required to meet to demonstrate that it is a good model of what is happening.

Future year scenarios are created by making changes to either the network and/or the trips. Local planning authorities will ask us to test the level of development in their local plans, and identify what transport improvements are needed. We will look at what areas become congested with the additional traffic and propose appropriate solutions. We also test our own road schemes in the same way.

Developers also ask us to test their developments (at their cost) through the model to inform their planning application. This is done by our consultants, so that we have confidence the information is correct, and we check that the various inputs are correct.

The model has a graphical interface package within it. This is used to extract data from the model which is normally included in a report on the modelling undertaken.

The model has to be updated every few years to ensure that it is up to date. This mostly means re-surveying the trips, but the network is also checked for changes. For future year models, things like changes in Local Plan allocations and addition of any more development granted planning permission are updated on a much more regular basis.