Our Ref:         FOI-2873-1920

Thank you for your request received on 20 December 2019 asking for information about the proposals for Holland Park Avenue.

Your request has been considered in accordance with the requirements of the Environmental Information Regulations and our information access policy. I can confirm we do hold the information you require.

The Operational Network Evaluator (ONE) Model is an operational highway traffic assignment model built in the VISUM software environment. The model is built as a simplified representation of the real world at a particular moment in time. The scope and scale of the model is in line with WebTAG guidance, which states:

“Within the Area of Detailed Modelling, a relatively high level of detail will generally be appropriate. Guidelines for Developing Urban Transport Strategies (Institution of Highways and Transportation 1996) suggests that “all roads that carry significant volumes of traffic” should be included and more generally that networks “should be of sufficient extent to include all realistic choices of route available to drivers.”

Due to the nature of assignment modelling and the assumption that users of the network have perfect information when deciding on a route, the inclusion of too many smaller roads will most likely result in an unrealistic amount of rat-running. For this reason only key strategic road and through routes are included in a strategic model, as outlined in WebTAG.

ONE reassignment modelling provides information on the likely redistribution of trips through the network following the implementation of a scheme. It can show where traffic flows are expected to increase or decrease across a wide area as vehicles redistribute through the network. This aides the design process by highlighting if the redistribution impacts are occurring in residential or sensitive areas. Designs can then be revised to mitigate these wider impacts, and a more detail assessment of the impact area can then be undertaken using microsimulation modelling.

The reassignment analysis for CS10 suggests mainly ‘forced’ reassignment, where traffic has to take a different path due to layout changes associated with the scheme. Some local north/south movements will be affected by changes such as the proposed southbound closure of Ladbroke Terrace, and it is likely that vehicles previously making this movement will move to parallel routes, such as via Ladbroke Road and south on Pembridge Road. The modelling also indicated that there might be a some rerouting of up to 200 vehicles travelling south using Clarendon Road and other adjacent roads. However, Clarendon Road has been simplified in our strategic model and is missing some details such as traffic calming measure. These details will be add into any future modelling to understand this reassignment in more detail. However, we would expect in reality this reassignment to be less.

The proposed implementation of contra-flow cycle lanes on Holland Park East and West is likely to result in traffic switching between these two roads for north / south movements.

Some traffic previously accessing Campden Hill southbound via Ladbroke Terrace is now predicted to meet Holland Park Avenue further west and use Aubrey Walk as an alternative route to Campden Hill Road. However, the modelling also predicts a decrease in traffic using Aubrey Walk northbound, with a corresponding predicted increase using Kensington Church St. The net change in traffic predicted to be using Aubrey Walk is therefore predicted to be negligible.

As part of the scheme proposals the number of traffic lanes on the Uxbridge Road eastbound approach to Holland Park Roundabout is to decrease, leading to a reduction in capacity on this approach. A small amount of reassignment is predicted northbound on Wood Lane / Ariel Way / West Cross Route as a result of this, in addition to a number of other alternative routes, which is modelling suggests will be well-spread with minimal increases in traffic flow.

Some wider reassignment of non-local traffic is also predicted, particularly for the AM peak, where a predicted increase of up to 200 vehicles per hour is expected to use A40 westbound to avoid the scheme area entirely, with an associated predicted reduction in traffic flow on Bishop’s Bridge Road and Westbourne Grove westbound.

The attached document shows the flow difference plots from the scheme consulted on in May 2019. Following the consultation, TfL has listened to the feedback and are making amendments to the proposed design. Traffic modelling will be undertaken to update the Base, Future Base, and Do Something (proposed) models to understand how the traffic reassignment and journey time will change. It is expected that the updated modelling results will be different to the attached current modelling.

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

Please see the attached information sheet for details of your right to appeal.

Yours sincerely

Gemma Jacob
Senior FOI Case Officer
FOI Case Management Team
General Counsel
Transport for London

[email protected]

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