APPENDIX C – TRUNK ROAD NETWORK PROCEDURES – ERSKINE BRIDGE

APPENDIX C – TRUNK ROAD NETWORK PROCEDURES – ERSKINE BRIDGE

INTRODUCTION

Purpose

Erskine Bridge is an exposed structure and it is essential that traffic control is applied during high winds to ensure that vulnerable vehicles are not exposed and blown over or blown into the path of other vehicles. This equally applies to pedestrians and cyclists potentially using the relevant pathways on it.

This plan identifies the specific wind monitoring and operational procedures to be adopted in response to predicted and actual high winds in the proximity of the Bridge.

HIGH WINDS

Taking cognisance of wind forecasting and warning information from the Meteorological Office and monitoring ‘live’ speeds provided by the wind data facility on the Erskine Bridge, graduated operational responses will be implemented to allow the majority of drivers continued use of the Bridge, until the final phase. These are as follows:

Stage 1 A ‘Warning’ phase implemented for wind gusts in the 35 to 44 mph range;

Stage 2 Procedures intended to advise of ‘segregation’ arrangements during
45 mph cross and 60 mph head/tail wind gusts, in order to divert
high-sided vehicles; and

Stage 3 Full closure of Erskine Bridge for wind gusts of 70 mph and above, irrespective of wind direction.

WIND MONITORING

Wind Forecast

Erskine Bridge is the subject of site-specific wind forecast/wind warning information provided by the Meteorological Office, as follows:

(a) Daily 5-day Forecast

This forecast is issued at approximately 0600 hrs each day and permits the Operating Company (OC) to plan and prepare for possible restrictions or closures. It is graduated and reflects rising wind speeds:

  • Green (G): maximum gust speeds 30 mph and below;
  • Amber (A): maximum gust speeds 31 to 44 mph;
  • Red (R): maximum gust speeds 45 to 59 mph; and
  • Black (B): maximum gust speeds 60 mph and over.

(b) Detailed Daily 24-hour Forecast

This forecast is also issued at approximately 0600 hrs daily and runs from 0700 hrs that morning to 0700 hrs the following morning.

(c) ‘Wind (Gale) Warning’ or ‘Wind (Storm) Warning’

Issued, if during the next 6 hours the maximum gust is forecast to exceed 45 mph or 60 mph respectively.

Live Wind Data

In addition, an ultrasonic wind anemometer is installed immediately above the centre bridge deck of Erskine Bridge and provides ‘live’ data and associated forecast information from the Met Office, on a web-based, large screen display within the OC Operational Control Room (OCR).

RESPONSIBILITIES

(a) Strathclyde Police

The police are empowered in terms of the Road Traffic Regulation Act 1984, Section 67(1) to close or instruct closure of a road in extraordinary circumstances, in order to mitigate potential danger. Consequently, in situations which raise concerns for safety, and with increasing wind velocities at the Erskine Bridge being within the recognised parameters, the Duty Engineer’s findings must immediately be intimated to Strathclyde Police for the police to decide and confirm approval for the implementation of ‘segregation’ or ‘full closure’ arrangements.

(b) Duty Engineer (24/7)

The OC Duty Engineer (D/E) will ensure that all wind related information for the Erskine Bridge is appropriately monitored and evaluated and, where appropriate, will instruct OCR staff to consult with the police, with a view to implementing procedures for either Stage 2 – ‘Segregation’ or Stage 3 – ‘Full Closure’. The D/E will be responsible for liaising with the Met Office to confirm forecasts and projections.

(c) The Operational Control Room (OCR)

The OCR will undertake continuous monitoring of wind data from the ‘live’ information feed on the web site, fully supporting the D/E in the wind
management arrangements for Erskine Bridge and liaising with Strathclyde Police. They will coordinate with Traffic Scotland in the implementation of each of the relevant stages.

(d) Duty Officer

In close liaison with the OCR, the OC Duty Officer (D/O) will be responsible for deploying all traffic management (TM) resources necessary to fulfil requirements to assist police in implementing the agreed stages’ response and updating staff with the relevant progress of TM operations.

(e) Traffic Scotland

Traffic Scotland will maintain close liaison with the OCR throughout the incident and will:

  • Implement the pre-arranged variable message signs (VMS) Plan to reflect the parameters of the particular Stage notified;
  • Undertake a cursory CCTV sweep of the visible bridge deck area for a ‘Full Closure’, in order to confirm an absence of vehicles to the OCR, after all TM operations have been completed;
  • Updating information on both Traffic Scotland and Freight Scotland web sites; and
  • At the completion of the incident, cancel associated VMS Plans only when a complete removal of all physical traffic management has been effected and when notified by the OCR.

MOBILISATION PROCEDURES

Stage / Wind Gust Speed

Actions

Stage 1

Wind gusts over
35 mph and less than 45 mph

‘Warning’ Phase

  • OCR to advise Strathclyde Police, with any additional information on potential restrictions or closure; and
  • OCR to advise Traffic Scotland with request for implementation of VMS plan showing ‘Caution High Winds’.

Stage 2

Cross wind gusts of 45 mph or Head/Tail wind gusts of 60 mph

 

‘Segregation’ Phase

  • D/E to direct OCR staff to advise Strathclyde Police of wind parameters. Strathclyde Police to decide to proceed with Stage 2 – ‘Segregation’;
  • OCR to advise Traffic Scotland of need to implement VMS plan showing ‘Erskine Bridge Closed To High Sided Vehicles’;
  • Incident support units (ISU) / TM Crews to implement pre-positioned drop-down signs indicating, ‘Erskine Bridge Closed to High Sided Vehicles’;
  • OCR to advise other Emergency Services;
  • ISU / TM Crews to implement closure of all gates on pedestrian/cycle paths on the Erskine Bridge, with the sign ‘Cycle Track and Footpath CLOSED – Dangerous Conditions’ being opened on each gate;
  • OCR and Traffic Scotland to liaise regarding circulation of advice to other agencies; and
  • Where velocities subside rapidly, restrictions must remain in place for at least 30 minutes from implementation, to reduce the potential for confusion which may occur with a shorter timescale.

Stage 3

Cross wind gusts and Head/Tail Wind gusts of 70 mph

‘Full Closure’ Phase

  • D/E to direct OCR staff to advise Strathclyde Police of wind parameters. Strathclyde Police to decide to proceed with Stage 3 – ‘Full Closure’;
  • OCR to advise Traffic Scotland and request that the VMS plan showing, ‘Erskine Bridge Closed’, be implemented;
  • ISU / TM Crews to thereafter assist police in implementing the agreed response by deploying TM for the physical closure of all slip and access roads;
  • OCR to advise other emergency services;
  • Gates on pedestrian/cycle paths to remain closed;
  • OCR and Traffic Scotland to liaise regarding circulation of advice to other agencies; and
  • Traffic Scotland to check bridge CCTV to verify that no vehicles are present.

Note: The temporary drop-down signs currently utilised at Stage 2 must be left open until reduced wind speeds allow them to be closed safely.

Wind gusts of
80 mph or more

Structural Examination

Where velocities of 80 mph or greater have been experienced, Erskine Bridge must be subjected to a structural survey as soon as reasonably practicable.

Traffic Management – Stage 2 (‘Segregation’)

Temporary drop-down signs intimating, ‘Erskine Bridge Closed to High Sided Vehicles’ are pre-positioned at the following locations and will be deployed in support of the primary VMS signs:

  • M8 (E) – On approach to the off-slip to M898;
  • M8 (W) – On approach to the off-slip to M898;
  • A82 (N) – On approach to the off-slip to A898 (Prior to advanced direction
    signs (ADS) at Auchentoshan Distillery);
  • A82 (S) – On approach to the off-slip to A898;
  • B815 (E) at Erskine – On approach to the roundabout giving access to the A898 northbound; and
  • A726 (W) at Erskine – Between the spectacle roundabouts, prior to the access slip to the A898 northbound.

Traffic Management – Stage 3 (‘Full Closure’)

The following actions to be undertaken by TM and ISU Crews to assist police in implementing the agreed response:

  • Closure of the northbound M898 at its access point from the M8 westbound;
  • Closure of the M898 from its merge point between the east and west bound
    off-slips from the M8, to the A726/B815 Bishopton/Erskine off-slip. This will physically compel all traffic to leave via the latter road;
  • Closure of the A726/B815 northbound on-slip from the ‘Spectacle’ Roundabout onto the bridge; and
  • Closure of the A82 westbound and eastbound on-slips onto the A898.

RE-OPENING PROCEDURES

A decision to re-open Erskine Bridge from either a Stage 2 (‘Segregation’) or a Stage 3 (‘Full Closure’), will be taken by the police on the advice of the D/E, who will have previously ascertained the following:

  • Whether the forecast wind gust speeds are expected to remain below the relevant speed and the wind direction is not expected to change adversely or blow from a more critical direction;
  • When reviewing a Stage 2 (‘Segregation’) scenario, it is important that
    removal is not undertaken where it is anticipated that it will possibly require a re-imposition a relatively short time later; and
  • Similarly, as a Stage 3 (‘Full Closure’) may require more than 1 hour to re-open and perhaps 1½ to 2 hrs to close again, re-opening should not be considered where there is potential of further closure within a few hours.

Sequence of Arrangements for Re-opening

The following Table lists the sequential removal of the relevant stages, listing associated procedures and responsibilities:

Stage / Wind Gust Speed

Actions

Reduction from Stage 3

Cross wind gusts and Head/Tail Wind gusts now reduced to less than 70 mph

Removal of ‘Full Closure’

  • D/E to direct OCR staff to advise Strathclyde Police of wind parameters. Strathclyde Police to confirm to OCR approval for removing Stage 3;
  • OCR to advise Traffic Scotland of intention to lift closure. (VMS text will not be altered at this stage);
  • ISU Crew or a Supervisor to undertake a safety inspection of the carriageway and its environs for debris etc. (e.g. lighting fittings), prior to re-opening;
  • TM Crews to remove physical closures on all slip and access roads for the Erskine Bridge, on both the South side (M8/M898 and A726/B815) and the North side (A82/A898), as two separate and individual operations;
  • TM Supervisor to report the physical re-opening of closures to the OCR as each group is achieved and, where wind speeds still remain within the Stage 2 banding, Traffic Scotland will be asked alter relevant VMS to indicate, ‘Erskine Bridge Closed To High Sided Vehicles’;
  • Temporary drop-down signs which had previously been deployed in Stage 2 of this operation and which will have been left open for safety reasons, will now be available to reflect and reinforce the message on the VMS;
  • Gates on pedestrian/cycle paths to remain closed;
  • OCR to confirm with Strathclyde Police that access roads are now open, although Stage 2 restrictions still apply; and
  • OCR and Traffic Scotland to liaise regarding circulation of advice to other agencies including updating of VMS.

Reduction from Stage 2

Cross wind gusts now less than
45 mph or Head/
Tail wind gusts
below 60 mph

Removal of ‘Segregation Arrangements’

  • D/E to direct OCR staff to advise Strathclyde Police of wind parameters. Strathclyde Police to confirm to OCR approval for removing Stage 2;
  • OCR to advise Traffic Scotland of intention to lift restrictions. (VMS text will not be altered at this stage);
  • TM/ISU Crews to close associated temporary drop-down signs for the Erskine Bridge on both the South side (M8/M898 and A726 / B815) and the North side (A82/A898), as two separate and individual operations;
  • TM Supervisor to advise completion to the OCR as each group is achieved and, where wind speeds still remain within the Stage 1 banding, Traffic Scotland will be asked alter the relevant VMS signs to indicate, ‘Caution High Winds’ on each side of the Erskine Bridge, as each is concluded;
  • TM/ISU Crews to re-open gates on pedestrian footpath/cycle track and re-set the signs on each, having ensured no debris is present;
  • OCR to confirm with Strathclyde Police that Stage 2 arrangements have now been lifted but with a Stage 1 – ‘Warning’ still in place; and
  • OCR and Traffic Scotland to liaise regarding circulation of advice to other agencies including updating of VMS.

Reduction from Stage 1

Winds speed gusts now below 35 mph

Removal of ‘Warning’ Signs

  • OCR to monitor diminishing wind speeds and will advise Traffic Scotland when reduced sufficiently to remove warnings from VMS; and
  • OCR and Traffic Scotland to liaise regarding circulation of advice to other agencies including updating of VMS.