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Hertfordshire County Council

We've developed a number of transport models for local planning authorities and developers to use as a common forecasting tool for all transport processes.

Hertfordshire is covered by COMET, our countywide strategic modelling tool. That's a suite of models which includes a Saturn-based highway model and EMME-based public transport and Variable Demand models.

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.

The model was built to represent typical weekday conditions in

  • AM (8–9am)
  • Inter peak (an average hour between 10am–4pm)
  • PM peak (5–6pm)

With the current base year representing 2014 and the main forecast year corresponding to 2036.

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

COMET Model Brochure (PDF 1.85MB) opens new window

In addition a COMET 2036 National Trip End Model (NTEM) has been developed for Hertfordshire County Council (HCC) to provide a useful starting point for certain model applications such as developer testing and potentially business case use.

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.

See the COMET model reference case brochure for more info (PDF 423kb)

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 through our Transport Planning Framework consultants, AECOM.  

To make use of these pre-existing models, please either contact us or complete the model test proforma (DOC, 151kb).

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


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 with us and AECOM to agree details of test.
  3. AECOM provide a costed specification 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. AECOM undertake the model test and supply required outputs.
  7. AECOM invoice us for the work. We then invoice the applicant (cost price of AECOM 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 AECOM 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 AECOM. 

See indicative model costs (XLS, 11kb)

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