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Read the Signs

Harbour masters have issued a warning to leisure craft after a narrow boat used a wrong bridge arch, forcing an oncoming passenger vessel to take avoiding action.

In a special Notice to Mariners, the Port of London Authority has alerted boaters to the dangers of not knowing what navigation lights and markers on bridges mean.

The PLA’s action has been prompted by an incident in November where a passenger vessel had its route blocked through Number 2 Arch at the northern end of Blackfriars Rail Bridge by a narrow boat on the wrong side of the river.

Harbour masters say that, had the passenger vessel arrived a few moments earlier, both vessels could have been in danger of collision within the confines of the bridge arch.

Instead, the passenger vessel took avoiding action.

A port authority patrol crew, called in to investigate the incident, intercepted the narrow boat further downriver and quizzed its owner.

He told them he’d become confused by the bridge navigation lights.

“At the time of the incident, there had been three closed arches at Blackfriars, where the bridge is being upgraded. There was a fourth arch showing ‘main working arch' lights, and a fifth showing no lights,” said a Harbour Master from the Port of London Authority.

“The narrow boater thought he had to use the ‘main working arch’ – which is designated for commercial vessels - even though it was on the wrong side of the river. He didn’t realise that he could use the arch showing no lights.

“Incidents like this show why it’s crucial that Thames leisure users fully understand the ‘rules of the road’ BEFORE they enter the tidal river.”

At-a-glance guide to bridge lights:

  • Three red discs or lights forming an upside-down triangle – indicates an arch which is closed and should not be used
  • Two orange (or amber) lights side by side - a main working arch (usually in the channel and usually used by commercial vessels)
  • No lights or signs showing – an arch available for navigation by vessels when height of tide, draft, air draft and good seamanship permit.

The PLA’s Notice to Mariners (19 of 2010) underlining the meaning of bridge lights is available here.  The PLA encourages all boaters to read this information before taking to the water.