Statement of Common Ground between Highways England & Central Bedfordshire Council [EXAM 111]

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Statement of Common Ground between Highways England & Central Bedfordshire Council [EXAM 111]

Statement of Common Ground between Highways England & Central Bedfordshire Council [EXAM 111]

Representation ID: 14260

Received: 01/07/2020

Respondent: Mr Roger Watson

Representation:

Highways England endorsement of the CBLTM model provides no confidence in its results, and fails to highlight known limitations of the model relevant to the A507 representation in particular.

A03
P10
Concerns that the Transport modelling used may not be accurate due to assumptions which need to be used.

Full text:

In para 3 Highways England (HE) endorse CBC’s use of the CBLTM Strategic Transport Model within the Local Plan. Given that HE use the same Saturn modelling software for their own Regional Transport Models, it would have been surprising if they had not done so. However, this does not guarantee any particular level of accuracy in the results, which are limited by the demand and network data fed in, and the assumptions on which the model is based.
The many roundabouts dotted along the A507 present a unique challenge to any modelling software. Standard techniques applied to 2-lane roundabouts on a single lane roads can over-estimate junction capacity by 50% or more. It is unlikely that HE considered this aspect in detail, but cannot be confirmed as no details of the model have been made available to the public. It would also appear that no attempt has been made to compare model predictions and actual (current) performance.
Over 2 years ago CBC commissioned a detailed study of the “A507 Corridor”, which was referenced in CBC Response to Initial Questions (EXAM 3). This was intended to address the limitations of standard modelling methodologies – publication of the results is still awaited.

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