Arch Closure Signage Safety Standards

In recent months, there has been a noticeable rise in reports of unserviceable and improperly rigged arch closure signage. Where works or activities are planned that require the closure of a bridge arch these must be approved by the harbourmaster, either through the licensing process or directly, and the signage must meet the requirements of Thames Byelaw 36. 

“Thames Byelaw 36. BRIDGES – SIGNALS IN ARCHES OR SPANS  

36.1 When the arch or span of a bridge is closed to navigation, the person in control of the bridge must display at or as close to the centre as practicable of that arch or span, or in a position agreed with the harbourmaster:  

                        a) by day, three red discs 0.6 metres in diameter at the points of an equilateral triangle with the apex downwards and the base horizontal; and  

                       b) by night, three red lights in similar positions to the discs displayed by day." 

It is critical to navigational safety that arch closure signage is fit for purpose. To assist river users and contractors, please refer to the technical specifications and rigging guidelines below. 

Technical Specifications 

In addition to the requirements laid out by Byelaw 36, the sign itself must meet the following requirements, unless otherwise approved by the Harbour Master: 

• The three red disks shall be backed on a white board with a height and width of 1.7m.  
• Dimensions should be as follows:

By night, the red lights must: 

• Be clearly visible in positions aligned with the centre of the disks. 
• Have a minimum range of visibility of: 

             1 Nautical Mile upstream of Thames Barrier and all creeks.  

             3 Nautical Miles downstream of Thames Barrier (excluding creeks) 

             5 Nautical Miles downstream of Queen Elizabeth II Bridge (excluding creeks) 

• Be unobstructed and clearly sighted from the river.  
• When battery powered, batteries must be replaced regularly as required to maintain the minimum range of visibility between sunset and sunrise, 7 days a week.  

Rigging Standards  

When rigging arch closure signage, any working arch lights must be extinguished. 

The positioning of arch closure signage must be such that they are clearly visible to river users, while not unnecessarily restricting sight lines through the arch. To ensure this, closure signage shall: 

• be positioned centrally on the arch. 
• be shown on both the upstream and downstream aspects of the bridge. 
• break the silhouette the arch.  
• at least 50% of the sign should extend below the bridge superstructure.  

If more than one arch is closed. Each arch must have its own arch closure signage.  

Positioning Examples: