Development assessments and modelling protocol

The information below is a summary of Warwickshire County Council’s (WCC) Modelling Protocol and describes each step of the process. For more guidance on each step, the relevant documents can be found under the documents and downloads section of this page.

Pre-app scoping

It is recommended that the applicant enter the formal pre-app scoping with Development Management to discuss modelling requirements.

Step 1: Site access strategy

Developer to confirm the site access strategy and proposed methodology for assigning development trips via the primary and secondary access points onto the surrounding highway network.

Masterplan layout of the site may need to be provided where there are multiple development parcels (or a large-scale development) or mixed use. This should indicate the likely number of units and area in development parcel.

Step 2: Trip generation

Trip generation is the first step in the process to estimate/predict number of trips, by purpose, that will be generated from a development.

Developer to create estimate:

Locally observed proxy data for the trip rates corresponding to the development, according to the characteristics of your site survey.
Data should be used to derive average vehicle trip generation for the proposed residential component of your development during a neutral month.
Use of TRICS database in accordance with WCC protocol.

Recommendation: Survey the site for at least 2 consecutive weeks to reduce any possible issue.

For more guidance, please refer to AN02a.2 - Multi-Modal Assumptions for Modelling (PDF, 197 KB).

Step 3: Trip rates

The trip rates should then be calculated using data from neutral weekdays (i.e. excluding Mondays and Fridays where trip profiles tend to differ from those on other weekdays) and Saturday. Typically, the trip rate should consider the following hourly periods indicated in the Protocol:

Weekday AM Peak: from 7am to 10am
Weekday PM Peak: from 4pm to 7pm
Saturday Peak (when applicable): from 11am to 2pm

Please refer to AN02a.2 - Multi-Modal Assumptions for Modelling (PDF, 197 KB) for further advice.

Note: During the pre-application stage WCC can offer advice on using different time periods required for trip rates if required.

Step 4: Validate against TRICS

TRICS requirements:

Select the land use according to each classification
On the land use and trip rate selection, exclude trips outside of mainland England and the cities due to the provision of public transport
Primary filter should be considering only surveys done on neutral weekdays (excluding Monday and Friday)
Finally, secondary filtering should exclude any unclassified land use class.

For more guidance please refer to AN02a.2 - Multi-Modal Assumptions for Modelling (PDF, 197 KB).

Step 5: Trip distribution

MND (Mobile Network Data) may be required to inform distribution patterns linked to development proposals. We would look to agree the LSOAs, to be included in the MND analysis, with you prior to you commissioning SLR to extract the data. For prices, please refer to our request Mobile Network Data pages.

Other forms of distribution methodologies might be recommended for specific land uses.

Please refer to AN02a.3 - Trip Distributions (PDF, 378 KB) for more guidance.

Step 6: Model licensing

Transport Assessment/Statements are required to support planning applications where applicable. Where significant development is proposed, WCC will use modelling thresholds to determine if the use of micro-simulation modelling is needed to support the Transport Assessment.

Responsibilities of Licensee

Use of WCC's models is to be agreed with WCC in advance.
The acceptability of the model for use will be subject to checking at the time of release and as well as any issues identified at the scoping stage. This will result in confirmation that the use of the model, for the intended purpose, is acceptable to WCC.

Please refer to AN01 - Model Licencing (PDF, 272 KB) for more advice.

Step 6a: Model thresholds

WCC require that any significant development is modelled using micro-simulation models where:

Trips associated exceed a threshold of 200 trips generated during the AM, PM or Saturday 3-hour peak periods and is situated in an urban area
Development creates a significant alteration to the highway network
Location at a point on the network is considered to be of strategic importance; or
The development is located at a point on the network considered to be significantly constrained
The development or traffic from it, is in an area of sensitivity due to environmental constraints (e.g. within an AQMA) or there is Council Member or public concern.

Note: If no model coverage exists for the area being considered the developer will need to discuss the best approach to developing a suitable micro-simulation model. WCC may develop a model to undertake the assessment and licence this to the developer.

For more guidance, please refer to AN01 - Model Licencing (PDF, 272 KB).

Step 6b: Junction modelling (if applicable)

If WCC considers impacts that need further investigation - developer will need to export Demand Flows from the relevant paramics model to inform isolated junction modelling within packages such as Arcady and LINSIG. Where junction modelling on ARCADY, PICADY (TRL Junctions software) or LINSIG is required, WCC will require:

The models and all input and output electronics files (i.e. .j11, vpo, .vpi, .lsgx)
Reporting on any changes to the default settings and any assumptions made
Use of queue markers to report on maximum and average queue lengths
Queuing may need to be plotted on a plan where one or more junctions require modelling or are affected by blocking back and queuing conditions.

For more guidance, pleaser refer to AN02b.2 - Use of Isolated Junction Models (PDF, 201 KB).

Step 7: Model scenarios

Model scenario requirements will be agreed with WCC in advance through scoping.

All testing should, in the first instance, consider the impact of any scheme proposals on the core scenario network.
If applicable, it is likely that it will also be necessary to consider the impacts of development proposals within the High Growth scenario.

Test 1 - The Year 1 Reference Case (run and report only) to provide the baseline conditions for comparison.

Test 2 - The Year 1 Development Case Do Minimum (The Test 1 network with the minimum infrastructure requirements and, if appropriate, the development trip generation proportionate to the year of assessment).

Test 3 - The Year 1 Development Case Do Something (comparing Test 1 and Test 2 networks and including targeted mitigation where necessary).

Tests 4 to 6 - If required, repeat test 1 to 3 using the second-year references case.

Test 7 - The High Growth Scenario (more often termed Local Plan Sensitivity Test - if the development being considered is also an allocated site then it is justifiable to consider its removal from this network prior to testing.

Test 8 - The High Growth Scenario with additional development assumptions as identified within tests 2/3 and 5/6.

Note: Year 1 would be the first identified reference case year.

For more guidance, please refer to AN02a.1 - Expected Model Scenarios (PDF, 197 KB).

Step 8: Model outputs

Model outputs are required to be provided in spreadsheet format.

Network statistics (for each modelled scenario)

Network Mean Delay
Completed Trips
Network Mean Speed

Queuing

Moderate increase (an increase in queue lengths of between 5 and 10 vehicles)
Significant increase (an increase in queue lengths of between 10 and 20 vehicles)
Very significant increase (an increase in queue length of over 20 vehicles)

Delays

No significant change (a difference in journey times of up to 5% falls within this category)
Moderate increase (an increase in journey times of more than 5% but less than 10%)
Significant increase (an increase in journey times of more than 10% but less than 20%)
Very significant increase (an increase in journey times, when compared to the Reference Case, of more than 20%)

Link flows

Link flows (directional and two-way flows)

For more guidance please refer to AN03.1 - Model Analysis and Reporting (PDF, 326 KB).

Step 9: Interpretation of results

Results should be provided in spreadsheet format with supporting commentary within the Transport Assessment.

Should the results indicate that there are discernible impacts at particular locations, we would normally ask you to provide confidence internal analysis primarily to show whether the impacts are directly attributable to the proposed development.

For more guidance, please refer to AN03.1 - Model Analysis and Reporting (PDF, 326 KB).

Step 10: Submission

All Traffic Models presented within the TA, either as the main assessments or as sensitivity tests, should be submitted to WCC via the Local Planning Authority, inclusive of the log runs relating to the model outputs.

It is acceptable for the models and log runs to be provided to WCC direct from the modelling consultant upon instruction from the licensee or their representatives.

For more guidance about the requirements for submission please refer to AN03.4 - Guidance on Submission upon Completion (PDF, 163 KB).

Please find below the archived documents. Current documentation can be found under the 'documents and downloads' section of this page.

Archived documents

Yes

It's good, but

No - here's why:

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