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Hertfordshire County Council


Countywide Model COMET

COMET is a multimodal transport model, developed using Department for Transport WebTAG guidance. It is able to predict changes in travel demand for vehicles, buses and rail.

It currently covers all A, B, main C roads and some key 'rat runs' in residential areas. Zoning is based on census MSOA areas.

See the COMET model coverage (PDF, 1.9mb)

Available Traffic Models in Hertfordshire (PDF 891KB)

Three main time periods are used to reflect typical weekday travel patterns in the model:

  • AM peak hour (8am-9am)
  • Inter-peak period (10am-4pm, hourly average)
  • PM peak hour (5pm-6pm)

It’s based on 2023 data, with forecasts looking ahead to 2043.

The current version of the model has been used to support district Local Plan evidence. 

COMET Model Brochure (PDF 1.58MB) opens new window

In addition to this, COMET 2029 NTEM and 2043 NTEM model scenarios have been created. NTEM refers to the National Trip End Model, on which demand forecasts are largely based. These model scenarios are designed to give a useful starting point for testing the likely impact of proposed developments and for business case development. 

Due to the intended purpose of this model (i.e. primarily a consistent starting point for developer testing), the certainty level of new transport schemes and planning data has been considered. New transport schemes have only been included if their certainty level is deemed by HCC to be “Near Certain” or “More than likely” according to the WebTAG definitions Table A2 WebTAG Unit M4 – Forecasting and Uncertainty.



Trip distribution reports

Trip distribution analysis provides estimates of how traffic flows into and out of specific areas. These estimates are generated using COMET and uses a range of data sources, including mobile phone network data, traffic counts, and journey time data.

The trip distribution reports model travel during COMET's three main time periods. Each trip has an origin zone and a destination zone - to analyse a specific area, relevant zones are selected, and the model estimates:

  • Where private vehicle trips are coming from when they travel into the selected area.
  • Where private vehicle trips are going to when they travel out of the selected area.
  • Where public transport trips are coming from when they travel into the selected area.
  • Where public transport trips are going to when they travel out of the selected area.

Each report includes tables showing estimated trip volumes and maps illustrating the likely routes taken.

Information:

Traffic model outputs are estimates and should not be used as a substitute for observed traffic flow data.


Local Models

In addition to COMET, we also have more detailed microsimulation-based local models in Hemel Hempstead, Hertford, Stevenage and Watford.

Whilst each of these models have different base years and coverages, they're potentially available to test developments and access arrangements in more detail than the strategic model.

Find out more:



Using the models

We encourage local planning authorities and developers to use pre-existing models where possible. You can commission bespoke option tests of the countywide model COMET by contacting our Transport Planning and Data Team.

To make use of these pre-existing models, please either contact us or complete the model test proforma (DOC, 146kb).

COMET Model Test FAQS: Frequently asked Questions and Answers (DOC 109KB)

Contact us about accessing the models...

Transport Planning and Data Team
Hertfordshire County Council

Email: Tpdata@hertfordshire.gov.uk

Phone: 01992 588 615

 

The commissioning process

The process is broadly:

  1. Complete the model test proforma (DOC, 128kb) providing details of trip generation and distribution, access arrangements and any associated mitigation schemes.
  2. Initial meeting / call to agree the details of the test with HCC’s Transport Modelling Team and a Development Management officer.
  3. HCC and Framework Consultants commit to providing a cost estimate and fee proposal to an applicant within 10 working days.
  4. Client needs to respond in writing, agreeing to specification to be provided.
  5. The test will then be commissioned through our Transport Planning Framework.
  6. HCC and/or an approved Framework Consultant(s) will undertake the model test and support with outputs.
  7. Framework Consultant invoices us for the work. We then invoice the Applicant (cost of model work plus additional Model Maintenance Fee). 

 

If you'd like to use the local town-based models, contact the Transport Planning & Data Team. Model runs can either be commissioned through our Transport Framework Consultant or, in some circumstances, can be supplied under licence (on agreement of a Memorandum of Understanding and Payment of a model usage and audit fee). 

 


Timescale and cost

Typically the process will take 6-8 weeks.

The cost of the work depends on:

  • the amount of coding required
  • the number of options to be tested
  • the level of reporting.

The cost will be confirmed in the specification provided by HCC. 

See indicative model costs (XLS, 10kb)

We charge a fee for modelling access and data supplied to organisations. We determine the fee by the type of data and the number of datasets requested. More about our data charging policy (PDF 131Kb).

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