Waterway signage

Larger waterways are more likely to use signage complying with international (CEVNI 1) or national standards; however, some waterways also have local signs.  It is absolutely essential to familiarise yourself with these before venturing onto the waterway.  Examples include the tidal Thames in London, where three red discs (daytime) or red lights (night) in an inverted triangle mean a bridge arch is closed, a bundle of straw by day or white light by night mean an arch has restricted headroom and an isophase white light illuminated on a bridge arch means a large vessel is approaching.