Transport evidence bases in plan making and decision taking

Guidance to help local planning authorities assess and reflect strategic transport needs in Local Plan making.

Transport evidence bases in plan making and decision taking

Why establish a transport evidence base for Local Plans?

It is important for local planning authorities to undertake an assessment of the transport implications in developing or reviewing their Local Plan so that a robust transport evidence base may be developed to support the preparation and/or review of that Plan. A robust transport evidence base can facilitate approval of the Local Plan and reduce costs and delays to the delivery of new development, thus reducing the burden on the public purse and private sector.

The transport evidence base should identify the opportunities for encouraging a shift to more sustainable transport usage, where reasonable to do so; and highlight the infrastructure requirements for inclusion in infrastructure spending plans linked to the Community Infrastructure Levy, section 106 provisions and other funding sources.

Local planning authorities should also refer to the Department for Transport’s Circular 02/2013: Strategic road network and the delivery of sustainable development.

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Revision date: 10 10 2014

What is the purpose of a transport evidence base to support the Local Plan?

A robust evidence base will enable an assessment of the transport impacts of both existing development as well as that proposed, and can inform sustainable approaches to transport at a plan-making level. This will include consideration of viability and deliverability.

A robust assessment will establish evidence that may be useful in:

  • improving the sustainability of transport provision
  • enhancing accessibility
  • creating choice amongst different modes of transport
  • improving health and well-being
  • supporting economic vitality
  • improving public understanding of the transport implications of development
  • enabling other highway and transport authorities/service providers to support and deliver the transport infrastructure that conforms to the Local Plan
  • supporting local shops and the high street

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Revision date: 10 10 2014

What key issues should be considered in developing the transport evidence base to support the Local Plan?

The key issues, which should be considered in developing a transport evidence base, include the need to:

  • assess the existing situation and likely generation of trips over time by all modes and the impact on the locality in economic, social and environmental terms
  • assess the opportunities to support a pattern of development that, where reasonable to do so, facilitates the use of sustainable modes of transport
  • highlight and promote opportunities to reduce the need for travel where appropriate
  • identify opportunities to prioritise the use of alternative modes in both existing and new development locations if appropriate
  • consider the cumulative impacts of existing and proposed development on transport networks
  • assess the quality and capacity of transport infrastructure and its ability to meet forecast demands
  • identify the short, medium and long-term transport proposals across all modes

The outcome could include assessing where alternative allocations or mitigation measures would improve the sustainability, viability and deliverability of proposed land allocations (including individual sites) provided these are compliant with national policy as a whole.

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Revision date: 10 10 2014

When should the transport assessment of the Local Plan be undertaken?

An assessment of the transport implications should be undertaken at a number of stages in the preparation of a Local Plan:

  • as part of the initial evidence base in terms of issues and opportunities
  • as part of the options testing
  • as part of the preparation of the final submission

The last of these stages should highlight the scale of and priorities for investment requirements and support infrastructure spending plans. Like a sustainability appraisal, it will be an iterative process and become more refined and detailed as the process draws to a conclusion.

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Revision date: 10 10 2014

What baseline information should inform a transport assessment of a Local Plan?

The following list indicates the key aspects that should be addressed in the transport assessment. This list is not exhaustive, and there may be additional issues that are important to consider locally.

  • all current transport issues as they affect all modes and freight covering, for example, accessibility, congestion, mobility, safety, pollution, affordability, carbon reduction across the whole Plan area and, within relevant areas of the Plan, including existing settlements and proposed land allocations
  • the potential options to address the issues identified and any gaps in the networks in the short, medium and longer term covering, for example, accessibility, congestion, mobility, safety, pollution, carbon reduction
  • the locations of proposed land allocations and areas/corridors of development and potential options for the provision of sustainable transport and transport networks to serve them
  • solutions to support a pattern of development that, where reasonable to do so, facilitates the use of sustainable modes of transport
  • the scope and options for maximising travel planning and behavioural change.
  • accessibility of transport nodes such as rail/bus stations to facilitate integrated solutions

The transport assessment should be produced at a Local Plan level in partnership with all relevant transport and planning authorities, transport providers and key stakeholders, for example, the Local Economic Partnership. It may be appropriate for the transport assessment to cover an area wider than the Local Plan at least initially given the size of some travel to work areas (this would be similar to the Strategic Housing Market Assessment). This process should help to identify any potential measures that may be required to mitigate negative impacts.

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Revision date: 10 10 2014

What detailed information is required for the transport assessment of the Local Plan?

Much information required for the transport assessment will already be available, not least from the development needs and land availability assessments. Local planning authorities will need to consider the demographics of the area and also the desired or perceived changes likely to take place in the life of the Plan as they might affect the transport network.

Other considerations that could be included are:

  • baseline existing conditions, which need to be established accurately to understand fully the context of the Local Plan policies and proposals
  • the existing integrated transport networks and any gaps in these as well as service and quality
  • opportunities to change to other forms of transport
  • the current use and demand by all different types of transport including cumulative trips into and out of the area
  • the availability of information from travel plans, previous assessments, transport operators etc
  • capacity data on rail and tram networks and constraints across the area
  • walking and cycling facilities and movements including future predicted trips
  • description and functional classification of the road network
  • current traffic flows including peak periods on roads, links and key junctions
  • parking facilities, including any park and ride and existing under-provision of off-street parking spaces
  • journey purpose of trips
  • identification and assessment of key links and junctions on the highway network to establish existing conditions
  • committed network improvements
  • personal injury accident records, including cyclist safety
  • any programmed public transport improvements including type, timing and promoter information
  • pollution, including baseline carbon emissions broken down by type of travel
  • existing transport-related environmental impacts
  • established best practice in transport provision and the share of each type
  • at a broad level, journey purpose and origin and destination currently and how it is likely to change or desired to change – for all types of transport

The above is not exhaustive, and other issues may need to be included as appropriate to give a complete baseline for the Plan area and how it will change. Early engagement between interested parties is important in agreeing the level and scope of assessment required.

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Revision date: 10 10 2014

How can a transport assessment of the Local Plan be undertaken?

A transport assessment is likely to be scenario based and in terms of projections look at a range of potential outcomes given a number of assumptions, for example, a movement in the proportion of people using different forms of transport consistent with best practice.

Transport data should be included that reflects the typical (neutral) flow conditions on the network (for example, non-school holiday periods, typical weather conditions etc) in the area of the Plan, and should be valid for the intended purposes. It should also take account of holiday periods in tourist areas, where peaks could occur in periods that might normally be considered non-neutral. The recommended periods for data collection are spring and autumn, which include the neutral months of April, May, June, September and October. Further advice is available from the Highways Agency, as described for traffic in the Design Manual for Roads and Bridges (Volume 13, Part 4).

In terms of road traffic, but not other types of traffic, where there is a need to project existing or historical traffic data for future year assessments, the preferred option is the use of appropriate local traffic forecasts (such as the Trip End Model Presentation Program used for transport planning purposes), provided they offer a robust assessment. In some cases, National Road Traffic Forecast growth rates would be appropriate. However, it is important to ensure that this does not just perpetuate existing travel patterns but, where reasonable to do so, facilitates the use of sustainable modes of transport.

The use of any area-wide traffic models or background growth rates should be agreed with the relevant transport or highway authority at the evidence gathering stage of the Local Plan. Care needs to be taken when considering using any model that it takes account of the need to address historic travel patterns not necessarily reinforce them.

To assess the availability of the capacity of the road network, the transport assessment should take into account:

  • recent counts for peak period turning movements at critical strategic junctions, for example, in certain instances where there is known to be a significant level of heavy goods vehicles traffic, a classified count (identifying all vehicles separately) should be provided
  • 12 hour/24 hour automatic traffic counts

Additional counts that may be required on the strategic parts of the road network could include:

  • manual turning counts (which should be conducted at 15 minute intervals) to identify all strategically relevant highway network peak periods
  • queue length surveys at key strategic signal junctions to establish demand and actual traffic flows
  • journey time surveys
  • freight counts
  • abnormal load counts
  • pedestrian and cyclists counts

Capacity assessments for roads, rail and bus should also be obtained.

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Revision date: 10 10 2014

How should the impact of land allocations be considered in assessing the transport implications of Local Plans?

The first step in quantifying the impact of proposed land allocations in the Local Plan on the transport system is to provide an estimate of the person trips (for all types of transport) that are likely to be generated by it.

In all cases, an analysis of development-related trips using an appropriate database or an alternative methodology should be agreed with the relevant highway authorities, as this will form the major element of the assessment.

An assessment of the impacts of the proposed additional land allocations can be initiated once initial potential allocations have been determined. There needs to be a description of the type of development at each of the locations proposed in as much detail as possible at the time. Where this is not possible, a “likely” scenario will need to be employed to set out the potential transport impact. Information that could be required includes:

  • location plans of each site
  • description of all the proposed land uses
  • scale of development – such as the number of residential units or gross floor area of development – subdivided by land use where appropriate/possible
  • site area in hectares
  • likely proposed access to existing transport infrastructure for all types of travel
  • where known, the likely proposed parking strategy
  • development phasing, where applicable
  • potential for securing travel planning benefits and enhanced sustainable transport provision

The above requirements are not exhaustive and will require adaptation to reflect the knowledge about the potential site allocations and developments as well as the type and scale of the proposed developments.

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Revision date: 10 10 2014

How should safety considerations be addressed and accident analysis used effectively in the transport assessment of the Local Plan?

All types of transport should be covered by safety considerations and accident analysis, taking into account the objective of facilitating, where reasonable to do so, the use of sustainable modes of transport. The level of detail required will be dependent on the stage of the Local Plan.

The transport assessment should identify any significant highway safety issues and provide an analysis of the recent accident history of the affected/impacted areas. The extent of the safety issue considerations and accident analysis will depend on the scale and type of developments in the context of the character of the affected Strategic Road Network. The need to minimise conflicts between vehicles and other road user groups should be adequately addressed.

Critical locations on the road network with poor accident records should be identified. This is to determine if the proposed land allocations will exacerbate existing problems and whether highway mitigation works or traffic management measures will be required to alleviate such problems. The accident records should be compared with accident rates on similar local roads.

Where the Strategic Road Network is involved, we recommend that appropriate national statistics are also used as a comparison.

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Revision date: 10 10 2014

How is the WebTAG approach useful in the transport assessment of the Local Plan?

An assessment should adopt the principles of WebTAG by assessing the potential impacts of development within the framework of WebTAG objectives. For most Local Plan assessments the full methodology recommended will not be appropriate. The Highways Agency’s Project Appraisal Report System may provide some useful guidance on methods more appropriate in these cases. Assessments involving major new transport infrastructure should, however, employ the methods set out in WebTAG.

Although this approach is typically applied when planning for local transport infrastructure, adopting this approach for Local Plan transport assessments will ensure that any proposed land allocation impact is considered in the context of two alternative scenarios – ‘with development’ and ‘without development’ – and will enable a comparative analysis of the transport effects of the proposed allocation.

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Revision date: 10 10 2014

Over how long a period should the assessment of the transport impact of the Local Plan cover?

The assessment should ideally cover the period of the Local Plan, taking into account all the changes and improvements in, for example, technology and behaviour that is likely to happen in that time. Circular 02/2013 sets out provisions for the Strategic Road Network and assessment years at paragraphs 25 to 27.

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Revision date: 10 10 2014

What should be considered in regard to the development of airport and airfield facilities and their role in serving business, leisure, training and emergency service needs? (National Planning Policy Framework paragraph 104)

Aviation makes a significant contribution to economic growth across the country, including in relation to small and medium sized airports and airfields (aerodromes). An aerodrome will form part of a larger network. Local planning authorities should have regard to the extent to which an aerodrome contributes to connectivity outside the authority’s own boundaries, working together with other authorities and Local Enterprise Partnerships as required by the National Planning Policy Framework. As well as the National Planning Policy Framework, local planning authorities should have regard to the Aviation Policy Framework, which sets out government policy to allow aviation to continue making a significant contribution (National Planning Policy Framework paragraph 80.

A working or former aerodrome could be put forward for consideration as a site for mixed use development (National Planning Policy Framework paragraph 118) that includes continuing, adapting or restoring aviation services in addition to other uses.

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Revision date: 13 03 2015

Updates to this page

Published 13 March 2015

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