FOI request detail

Traffic models and data outcomes for the CS11 northwards extension

Request ID: FOI-1035-1718
Date published: 22 August 2017

You asked

Re: FOI-0797-1718/GH Thank you for your reply to Redington Frognal Association's query on the TfL traffic models utilised to assess changes in traffic on side roads leading from Finchley Road between Briardale Gardens and Swiss Cottage. You said that plans to extend CS11 from Swiss Cottage to Hendon Way are not now being pursued and that you are not actively working on any traffic models for CS11 north of Swiss Cottage. However we asked for this information in order to understand the effects of the Swiss Cottage scheme on local roads. We would find it surprising if you had not looked at the effects of the Swiss Cottage scheme on side roads north of Swiss Cottage and we should like to have any data you possess relating to these roads. We are glad that TfL recognises the potential repercussions for traffic in the local area, but do not feel that our concerns have been fully addressed in the response. In particular, Appendix A states: As with the proposals consulted on, there is still likely to be reduced flow along Fitzjohn’s Avenue leading into College Crescent, although as a result of the recommended changes this reduction is smaller than previously. We also expect to see a decrease in traffic on Parkhill Road in the morning peak. As a result of the changes we have made to the proposals, we no longer expect to see a significant increase in traffic on Heath Street, Rosslyn Hill, West Heath Road, Hampstead High Street or Arkwright Road. However, there is now likely to be an increase of traffic on Belsize Avenue and Belsize Park and also on on Haverstock Hill towards Chalk Farm Underground station as the wider area impacted as a result of the proposals reduces. We should like to see the current and predicted vehicle flows and movements for all of the roads mentioned by you above, as well as for Finchley Road and the roads leading east from Finchley Road between Frognal and Pattison Road, and the names of the traffic models. We are seeking traffic data at different times of the day, week and year. It would in any case be helpful to have the base data, in order to have a point of reference, including for when applications are submitted to extend pupil numbers at the many schools in the area.

We answered

Our ref: FOI-1035-1718/GH

Thank you for your request received by Transport for London (TfL) on 31 July 2017 asking for further information about traffic modelling.

Your request has been considered under the requirements of the Environmental Information Regulations and our information access policy. I can confirm that we do hold the information you require. Please see the attached traffic models and data outcomes document.

All modelling undertaken by TfL complies to WebTAG standards as set out by the DfT. More information can be found at Traffic models are predictive tools used to better help plan, design and operate the transport network. Models are designed as simplifications of the real world, at a particular moment in time, averaged over an observed period and are used to evaluate the impact, both positive and negative, of future network interventions.

The strategic modelling for the CS11 proposals utilises the North London Highway Assignment Model (NoLHAM) which is built in the SATURN software platform, created and maintained by TfL.

Strategic reassignment modelling provides information on the likely redistribution of trips through the network following the implementation of a scheme. The results are representative of network conditions sometime after the changes have been implemented, when individuals have learned of alternative routes and chosen the one best suited to them. The results produced from this modelling are only ever indicative and is intended to give an idea of where the impacts of changes in journey are likely to occur on the network. It assumes that all drivers have perfect knowledge of the network and will always choose the quickest route available.

The results presented show the results from three incremental model scenarios; Base, Future Base and Do Something

  • The Base model represents the current situation on the network before any work is carried out


  • The Future Base model represents the future year in which the scheme under consideration is planned to be implemented but assumes the scheme itself is not implemented


  • The Do Something model represents the future year, in which the scheme under consideration is planned to be implemented, including the scheme itself. Comparisons between this scenario and  the Future Base allow for the only the impacts of the scheme underassessment to be appraised

If this is not the information you are looking for, or if you are unable to access it for some reason, please do not hesitate to contact me.

If you are not satisfied with this response please see the attached information sheet for details of your right to appeal.

Yours sincerely

Graham Hurt

FOI Case Officer

FOI Case Management Team

General Counsel

Transport for London


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