The National Day ferry disaster inquiry is investigating when the wires were cut to two lights onboard the Lamma IV. Paul Shieh Wing-tai SC, the counsel for the commission of inquiry, yesterday said wires to a masthead and an anchor light had been found cut. But it was unclear if the wires had been severed during the rescue operation. Johnny Mok Shiu-luen SC said that the police and the Marine Department, which he represents, had confirmed that they and their experts had neither cut nor tampered with the wiring on the launch. Commission chairman Mr Justice Michael Lunn told lawyers for all parties - including Hongkong Electric, the owner and operator of the Lamma IV - to liaise to find out when the wires were cut. The inquiry is looking into the collision between Hongkong Electric's Lamma IV ferry and the Hong Kong & Kowloon Ferry's Sea Smooth catamaran on October 1 last year, in which 39 people died. The assistant director of the port control division at the Marine Department, Raymond Chung Siu-man, yesterday spoke to the commission about the vessel traffic services system. The system monitors marine traffic and provides navigational safety. It raises collision alerts for participating vessels when they come within a certain distance of vessels that are at least 35 metres in length. For participating vessels, the system raises collision alerts when vessels are deemed to be too close to each other. Vessels that participate in the system are ocean-faring and river-trade vessels. The system filters out vessels smaller than 35 metres. I have tried to demonstrate that if [the filter were removed], the whole screen would be full of alerts The Lamma IV, a 27.21-metre launch, and Sea Smooth, a 28.02-metre catamaran, did not participate in the system. Chung said that if there was no filter, a 23-minute journey starting at 10.32pm from Yung Shue Wan to Central on February 10, which was a Lunar New Year public holiday, would have triggered six collision alerts. This would have required a system operator to call the coxswain six times to alert him to possible danger. Removing the filter on a regular day would have imposed a "very heavy additional burden" on the operators, he said, noting that his estimates were "an understatement". "I have tried to demonstrate that if [the filter were removed], the whole screen would be full of alerts," he said. Figures provided to the commission of inquiry showed that the annual collision rate for local passenger vessels varied between 0.001 and 0.003 per cent of the total number of trips by franchised and licensed ferry services and kaitos between 2008 and 2012.