According to the latest Signal Group data, 62 per cent of 102 recorded tanker transits were completed with the Automatic Identification System, or AIS, switched off. The practice was particularly widespread among crude carriers, with 33 of 42 transits, 79 per cent, taking place without an active signal. By comparison, 30 of the 60 clean petroleum and product tanker crossings were AIS-dark, meaning the rate among those vessels stood at 50 per cent. Traffic continued in both directions, with 55 ships travelling from east to west and 47 moving in the opposite direction. For a tanker worth $100 million, that translates into a potential insurance bill of between $3 million and $10 million for a voyage through the region.