Hydrosphere director Jeff Gibson said, 'Many harbour lights have evolved in different ways, meaning a lot of confusion for the poor old sailor. The IALA system makes things easier and introduces some consistency.' 

The harbour opted for a simple light array that either reads 'red-red-red', meaning the ferry is berthing, or 'green-green-white', meaning that boats can proceed, but watch out for two way traffic.  

The next step in the planning was to find out exactly how much light needed to be thrown in order that incoming traffic could see the signals. 'The signals rely on being able to be seen from half a mile away, out at the anchorage, during daylight hours.

This may not seem much, but getting a light seen from this distance takes a lot of power, said Gibson. 'We opted for standard Vega marine beacons, and a combination of two lights at each position. During the day, the harbour uses both lights to give increased intensity, and lowers this to a single light at night, coming down to a third of daylight output, to reduce blinding.'  

Gibson explained that many ports use halogen lights with coloured screens in front, not an ideal solution since it is wasteful on power, and only gives a limited result. 'We decided we needed an output of around 1,000 candela per position, which meant 30 Watts of power for a 360 degree arc, he continued. 'This is in comparison with a halogen light, which roughly compares as taking up 30 Watts and only giving a 40 degree arc output.'  

The lights are controlled by radio signals from the Harbour Master's office on the other side of the dock. The project took some eight weeks from planning to installation, although the actual erection of the signal mast only took two days, as it arrived on site with most of the hardware ready to be fitted.