Publication - FOI/EIR release

M8 Woodside Viaduct Permanent Solution: EIR release

Published: 30 April 2026
Topic: Public sector, Transport
FOI reference: FOI/202600509623
Date received: 4 March 2026
Date responded: 1 April 2026

Information request and response under the Environmental Information (Scotland) Regulations 2004

Information requested

At the Woodside Hall public consultation on the M8 Woodside Viaduct today 4 March a display 'Approach 3: Remove' included findings produced by a consultant showing what the effect of removing a section of the motorway viaduct M8 at Cowcaddens would be using traffic modelling.

The display of the results of traffic modelling appears to heve been contrived to suggest that removing a section of the M8 would disadvantage travellers currently using the M8 when, with appropriate new and changed infrastructure, they could have good more sustainable transport provision (eg SPT franchised buses and trams using priority lanes along the line of the M8, with park and ride, etc.).

Please send me a copy or link to:

(1) All superseding responsibilities in the 2010 framework document transport-scotlandframework-document.pdf that summarize the current scope of TS responsibilities which then included section 3.5 'to promote transport integration and maintain a clear outward focus on the needs of transport users'.

(2) The minutes or account of the meetings (elected members and/or officers) which decided or ratified the spending of money on traffic modelling to consider only what happens if a section of the M8 is removed with no account to be taken of new infrastructures and changes.

(3) The brief given to the consultant explaining the scope of what TS requred them to model.

(4) The name(s) of computer sofware, AI and other tools used by the consultant to assist in the creation of the model.

(5) The technical report produced by the consultant given to TS as work done.

(6) All correspondence between consultant and TS concerning the scope of the modelling, what was actually done and clarifications made subsequently.

(7) Dates of meetings and the discussions that considered the scope of modelling – including with Cabinet Secretary and elected members, committee(s).

(8) All meeting minutes and accounts of discussion in TS that concluded the modelling should not take in consideration any changes, modifications or additions to city infrastructure that would enable new traffic flows and transportation, such as improvement in public transport which SPT is committed to providing by franchising bus services.

Response

As the information you have requested is ‘environmental information’ for the purposes of the Environmental Information (Scotland) Regulations 2004 (EIRs), we are required to deal with your request under those Regulations.

We are applying the exemption at section 39(2) of the Freedom of Information (Scotland) Act 2002 (FOISA), so that we do not also have to deal with your request under FOISA. This exemption is subject to the ‘public interest test’. Therefore, taking account of all the circumstances of this case, we have considered if the public interest in disclosing the information outweighs the public interest in applying the exemption. We have found that, on balance, the public interest lies in favour of upholding the exemption, because there is no public interest in dealing with the same request under two different regimes. This is essentially a technical point and has no material effect on the outcome of your request.

It may be helpful to first explain more about the traffic modelling referred to in your request for information before responding to each of your requests.

The traffic model used is the Strathclyde Regional Transport Model (SRTM), which has been developed using industry-standard software for transport projects. The SRTM considers both road traffic and public transport journeys and forecasts changes over time up to 2045. Observed data is used to develop the model to ensure it replicates current traffic flows, congestion and delays to journey times, as observed, to develop a baseline from which to produce forecast projections of traffic levels.

The development of this model is described in more detail within the reports at the links below:

https://www.transport.gov.scot/media/48289/website-srtm14-road-model-development-report.pdf

https://www.transport.gov.scot/media/48291/website-srtm14-demand-model-development-report.pdf

The set of models described above were used to test the following scenarios, which informed the public engagement:

Reference Case - 2025, 2030 & 2045 SRTM Reference Case - (S01) The reference case scenario assumes all M8 Woodside Viaducts lanes are in operation for traffic.
M8 Woodside Viaducts Closure Test - 2025 SRTM Woodside Closure Test - (S02) This scenario assumes the M8 corridor is closed between J16 and J17 to all traffic.

Assumptions, Data Sources and Approach

The SRTM was developed and validated by incorporating observed real-world data that includes traffic volumes and journey times to ensure the model provides a suitable representation of the traffic network in Glasgow.

The traffic count data is taken from a permanent traffic count database owned and operated by Transport Scotland. These are permanent count sites that provide long term trends along key sites of the strategic road network.

The journey time data is provided by the INRIX (Leading Transportation Analytics Soutions) database that collects this data by aggregating, in real-time, Global Positioning System (GPS) probe data from the road network. These are a combination of real time journey time data from connected and fleet vehicles, mobile phone apps and smartphones. This provides a comprehensive dataset that provides journey time data along the M8 corridor and alternate routes.

Estimates of traffic changes

As part of the Feb/March 2026 public engagement, a map was prepared to demonstrate the potential traffic impacts of closure of the Woodside Viaducts. This ‘heat’ map was based on comparison of differences between the modelling outputs for the reference case and the closure test and visually demonstrates the differences in vehicle levels on the strategic and local roads network in response to a viaduct closure scenario.

Please note that the blue arrows on the map are purely illustrative and indicate the alternative trunk road connections connecting the M8 to the M74, M80 and M73.

I have responded to each of your requests for information as follows;

(1) All superseding responsibilities in the 2010 framework document transport-scotland-framework-document.pdf that summarize the current scope of TS responsibilities which then included section 3.5 'to promote transport integration and maintain a clear outward focus on the needs of transport users'.

The current version of the Framework With Ministers document summarises how Transport Scotland and Scottish Government will work together, and the key roles and responsibilities of the Scottish Ministers, the Chief Executive and their Accountable Officer role at Transport Scotland and the Portfolio Accountable Officer within the Scottish Government, whose remit includes Transport Scotland.

Our Corporate Plan 2024-27 sets out how, as an Executive Agency of the Scottish Government and Scotland’s national transport agency, we focus our activities on delivery through our National Transport Strategy, the transport-driven National Outcomes within the National Performance Framework (NPF) and the Programme for Government (PfG).

Please note that traffic modelling work for the M8 Woodside Viaducts Permanent Solution project is part of a wider commission, the scope of which is set out in the Services Brief for the commission, further details of which are provided below within the response to question 3 below.

The modelling work was developed iteratively with WSP’s subconsultant Systra, a specialty engineering and consulting group. Systra, who have previous experience using the Strathclyde Regional Transport Model, have access to the model via their place on Transport Scotland’s Transport and Land-Use Modelling, Appraisal and Transport Planning Services (LATIS) Framework, which appointed consultants to carry out services in connection with transport and land-use modelling, transport appraisal and planning.

The work was developed to align with Strategic Business Case submission timescales and allocated budget, subject to award constraints under the LATIS Framework. Initial meetings were held with Transport Scotland, Systra and WSP to agree the appropriate scope, please see response to question 7 below for further details.

In line with standard transport modelling practice, schemes which are not committed development (i.e. have current planning permission) were not included in the appraisal, and as there are currently no committed infrastructure schemes, no other infrastructural changes were modelled. Please see attached Annex A which includes an extract of some of the information requested. Please note that some of this information has been redacted, and refer to exception details below.

Regulation 11(2) of the EIRs (personal information)

An exception under regulation 11(2) of the EIRs (personal information) applies to some of the information you have requested because it is the personal data of a third party. While our aim is to provide information whenever possible, in this instance a small amount of information, i.e. names of junior Scottish Government officials and employees of other organisations, have been redacted. This exception applies because disclosing it would contravene the data protection principles in Article 5(1) of the General Data Protection Regulation and section 34(1) of the Data Protection Act 2018. This exception is not subject to the ‘public interest test’, so we are not required to consider if the public interest in disclosing the information outweighs the public interest in applying the exception.

(3) The brief given to the consultant explaining the scope of what TS requred them to model.

Please find below an extract of the Services Brief for the commission which summarises the Transport Modelling scope of work for the M8 Woodside Viaducts:

4.14. Work Package 14: Transportation Operational and Economic Assessment

4.14.1. This Work Package may typically include the following Services:

Some traffic survey information is available in relation to the monitoring of the temporary traffic management for the propping works. The consultant should review the information available and agree what further work is required with the Employer;
It is not envisaged that a new traffic model will be required to be developed for the project but the consultant shall liaise with the Employer to confirm what modelling tools may be available and/or to agree a proportionate method for understanding the current and desired future traffic operations in the locality;
The consultant should design, procure and supervise any additional survey work as required. The cost of the survey will be reimbursed by the Employer as Special Works;
The Consultant shall be responsible for undertaking operational and economic assessment for the project as appropriate. Where no recognised method for calculating economic benefit is available, the consultant shall augment the quantification of benefits with a qualitative case based on policy and stakeholder survey work and the like;
The operational and economic assessment shall be subject to Scottish Government audit procedures; and
The Consultant shall make provision for this work in its programme of work activities.

The modelling work undertaken from the initial brief was developed iteratively between Transport Scotland, WSP and Systra, working within the confines of the timescales and within the allocated budget, and the agreed scope of work requested of Systra is set out below.

1. Scoping Modelling Tasks, tests, outputs, commissioning and project management and communication

Systra would discuss option tests and help specify the detailed model inputs required to represent test options. Systra would provide regular progress updates, present emerging model outcomes to the WSP team, and provide various data sets and analysis. This would include feedback on the performance of the model / test results and discussion of any uncertainties relating to the modelling and consideration of further updates.

2. SBC Modelling - Light touch 2025 current scenario modelling
To inform the initial SBC modelling, Systra will run a Light touch network update with a VDM assignment with the only change to the existing Reference Case Scenario being to reduce the M8 capacity to 2 lanes between J18 to J16 (WSP will provide coding updates to reduce the number of lanes to 2 on the M8 only) plus the current closures of the J17 slip roads and Phoenix Road, plus the closure of the J18 westbound slip road. This assessment will involve coding lane reductions on approximately 9 links on the M8 and closing specific J17 and J18 slip roads to reflect the potential contraflow arrangement. No other network updates on local roads are to be included in this assessment to be consistent with existing forecast year model scenarios – REF and D05 (see below). It has been suggested to run the full VDM for both forecast years (2030 and 2045). This will provide a consistent set of model scenarios to provide the following list:

REF - 2025, 2030 & 2045 SRTM Reference Case
WVC- 2025, 2030 & 2045 SRTM Woodside Closure Test
M8 with 2 lanes and: J17 eastbound-on and westbound-off slips closed; J18 westbound off slip closed; and Phoenix Road closed – 2025, 2030 & 2045 (to reflect potential contraflow working)

This will provide sufficient evidence for the SBC modelling stage

3. Provision and coding of updates in 2025 Baseline, & Future Year Scenarios – OBC Modelling

As part of the OBC modelling, Systra would work with WSP to determine and code up the range of updates required into SRTM to represent the local study area network. This would include a number of updates Systra has recently identified for other projects, which have helped reduce model noise effects within the congested network. Coding updates are thought to be relatively extensive and would be input to the 2025 scenario and subsequent Forecasts for consistency. Coding Updates will include those provided by WSP on 23/07/2025.

The 2025 scenario would initially be run as a fixed matrix, but also run with full VDM to ensure consistency when comparing 2025 to 2030 scenario changes over time (and due to the number of updates involved).

A high-level check would be undertaken on SRTM demand matrices to identify if the updates have changed the overall travel demand significantly.

4. Initial closure test (fixed Matrix, further updates)

Systra would test the initial response of the SRTM by undertaking a simplistic full M8 closure test to understand if the re-routing impacts are intuitive in each time period (2030 Without Policy). This would provide traffic flow plots and congestion impacts to identify initial impacts and the performance of the modelling. Through a combined WSP / Systra review, this is likely to lead to identifying some further updates required along alternative routes, which would be coded into the models.

5. Comparison of 2025 Local Traffic Volumes / Journey Times

Systra would extract a range of total traffic flows and road journey times to compare with observed data. These would provide a cross-check if the current model flows were generally representative with current traffic conditions. These flows and journey times would be provided to WSP to compare with observed data.

6. Full VDM Do Minimum (2030, 2045, Without Policy)

Systra would run the full SRTM 2030 and 2045 demand models to take account of the Baseline coding updates within the future years for comparison purposes.

7. Full VDM Closure Tests (Without Policy)

The following full VDM tests would be undertaken for the 2030 and 2045 scenarios. The technical details of the closures will be agreed with WSP.

A. M8 Open J17 Open Phoenix Road Closed

Test the long-term impact of a full closure of the local network access. Traffic operational results would be provided in terms of overall network congestion, Veh Kms and re-routing plots.

B. M8 Closed Local Open

Test the long-term impact of a full closure of the M8. Traffic operational results would be provided in terms of overall network congestion, Veh Kms and re-routing plots.

C. M8 and Local Access Fully Open

Provide a scenario and outputs with no network closures or traffic management.

8. Fixed matrix M8 traffic management Tests (Without Policy)

Systra would code up and run each of the two defined option tests within the 2030 and 2045 scenarios using either Do Minimum or VDM demand from the tests listed above (TBC). These options are to be confirmed when the preferred options for detailed modelling are selected at the conclusion of the SBC.

9. Traffic flow, Veh Kms, journey time / traffic delay analysis

Systra would undertake a range of road traffic analysis for each test to review and demonstrate the impact of each option across the network.

Analysis would be provided within Spreadsheets and PowerPoint files Including Veh / Car Kms / Veh Time / time lost due to congestion, demand matrix summary stats, traffic volume changes and flow plots. Systra would also work with WSP to confirm and provide model files required to support presentational analysis (i.e. providing .csv and shape files of the network flows for input to the WSP online analysis process).

Economic skim outputs are not anticipated at this stage but could be prepared if required for an additional fee.

10. Modelling Summary Note

Systra would prepare a Model Assessment summary note documenting the model updates, traffic volume comparisons, range of tests undertaken and the outputs provided as part of the study.

Please see the response to question 7 below for further details of specific meetings.

(4) The name(s) of computer sofware, AI and other tools used by the consultant to assist in the creation of the model.

Modelling was carried out using an existing transport model rather requiring creation of a new model. The transport model used was the SRTM. This model runs in the industry-standard SATURN transport modelling software. The model also incorporates measures of travel demand (route choice, transport mode choice, and usage numbers) from the software CUBE. Further details of the transport model can be found in the documents linked above.

(5) The technical report produced by the consultant given to TS as work done.

There is no completed stand-alone technical report on traffic modelling work. Information presented at the public exhibition reflects emerging assessment findings, which are in the process of being collated and reported in a Strategic Business Case for the project. As this work is incomplete, we are unable to provide a copy of the report requested.

Regulation 10(4)(d) – material in course of completion, unfinished documents or incomplete data

An exception under regulation 10(4)(d) of the EIRs (unfinished or incomplete information) applies to all of the information you have requested because it is material which is still an unfinished document. This exception is subject to the ‘public interest test’. Therefore, taking account of all the circumstances of this case, we have considered if the public interest in disclosing the information outweighs the public interest in applying the exception. We have found that, on balance, the public interest lies in favour of upholding the exception. We recognise that there is some public interest in release as part of open, transparent and accountable government. However, this is outweighed by the public interest in ensuring that incomplete information which is still in being worked on is not disclosed when it might misinform the public or give a misleading impression of the Government’s view or position on the matter to which the information relates.

(6) All correspondence between consultant and TS concerning the scope of the modelling, what was actually done and clarifications made subsequently.

As noted in the response to question 3 above, the general scope of the traffic modelling work was set out in the Services Brief for the commission and the details scope of the modelling works was developed iteratively between Transport Scotland, WSP and Systra.

Further correspondence on traffic modelling between Transport Scotland and its consultant regarding work undertaken is attached in Annex B. Some of this information has been redacted, please refer to exception details for Regulation 11(2) of the EIRs included in question 2 answer above.

(7) Dates of meetings and the discussions that considered the scope of modelling – including with Cabinet Secretary and elected members, committee(s).

The scope of traffic modelling work for the M8 Woodside Viaducts Permanent Solution project was discussed at meetings held on the dates listed below.

1 May 2025 meeting between Transport Scotland and WSP to discuss overall approach to modelling and the tools and data available (minutes enclosed in Annex A).
23 May 2025 meeting between Transport Scotland, WSP and Systra to discuss accessing and updating existing models. It was in this meeting where a ‘closure test’ was agreed to be conducted, so that the local junctions that would be most impacted could be identified (minutes enclosed in Annex A).
22 July 2025 meeting between Systra (who run the transport model on behalf of Transport Scotland) and WSP to discuss modelling requirements (minutes enclosed in Annex A).
19 November 2025 SBC Content Presentation meeting between Transport Scotland and WSP. In this meeting the results of the strategic traffic modelling were discussed (minutes enclosed in Annex A).

Following these initial inception meetings, regular discussions were held regarding the delivery of the modelling as follows:

Weekly meetings between Systra and WSP at 9:30am on Friday from 14 November onward. The updates from these were communicated on a monthly basis to Transport Scotland as part of regular dashboards.
Weekly internal meetings within the WSP modelling team at 9am on Tuesdays; these meetings are comprised of WSP staff working on the commission from graduate to technical director level.
Weekly meetings with the Business Case team (Transport & Mobility) on Tuesdays at 1:30pm. This meeting is comprised of representatives from the WSP sub-teams focused on the M8 Woodside Viaducts business case development. Staff at these meetings are based in WSP’s transport modelling and transport planning teams.

Transport modelling was also discussed at most Transport Scotland / WSP monthly update meetings, though these discussions were largely about the commercial arrangements, which are outside the scope of the request. Therefore, please see attached Annex A which includes extracts of meeting notes relevant to discussions that considered the scope of modelling. Please note some of this information has been redacted, please refer to exception details for Regulation 11(2) of the EIRs included in question 2 answer above.

List of Transport Scotland / WSP monthly meeting notes included in Annex A detailed below;

17 June 2025
17 September 2025
19 November 2025
10 December 2025
21 January 2026

In regard to discussions including Cabinet Secretary and elected members, committee(s), I can confirm that the scope of traffic modelling work has not been discussed at meetings involving the Cabinet Secretary, elected members or committees of the Scottish Parliament. Please refer to exception details below for information not held.

Regulation 10(4)(a) of the EIRs (information not held)

Whilst our aim is to provide information whenever possible, in this instance Transport Scotland does not have the information you have requested. We do not hold dates of meetings and/or discussions that considered the scope of modelling with Cabinet Secretary and elected members, committee(s).

Under the terms of the exception at regulation 10(4)(a) of the EIRs (information not held), Transport Scotland is not required to provide information which it does not have. This exemption is subject to the ‘public interest test’. Therefore, taking account of all the circumstances of this case, we have considered if the public interest in disclosing the information outweighs the public interest in applying the exemption. We have found that, on balance, the public interest lies in favour of upholding the exemption. While we recognise there may be some public interest in, dates of meetings and/or discussions that considered the scope of modelling, including with Cabinet Secretary and elected members, committee(s), clearly, we cannot provide information which we do not hold.

I refer you to the response to questions 2 and 7 above. The meeting on 23 May 2025 was most relevant to this issue. A extract of this meeting note has been provided in Annex A. Please note some of this information has been redacted, please refer to exception details for Regulation 11(2) of the EIRs included in question 2 answer above.

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