Real Journeys' coach services manager, David Osborne, said the company was trialling the Trac Plus system, primarily used in the New Zealand aviation industry particularly for search and rescue missions, to see if it should be fitted to its entire fleet.
There was virtually no cellphone contact on the Milford Rd and the high surrounding mountain ranges and deep valleys made radiocontact almost impossible.
In addition, only two land-based telephones were available on the way to Milford Sound and there were periods of about an hour when no communication was available with the coach driver.
The issues were highlighted in 2002 when 32 Singaporean tourists escaped from a flaming coach in the Homer Tunnel - 103km from the nearest emergency services at Te Anau. Thirty of the passengers walked through the pitch-dark and smoke-filled tunnel to safety, while two passengers became separated and made their way to the Milford end of the tunnel.
A satellite phone and fire extinguisher were installed in the tunnel as a result.
In 2008, two tourist buses were destroyed by fire outside the tunnel. No passengers were injured in either incident, with the satellite phone and fire extinguisher put to good use.
Mr Osborne said those incidents had highlighted issues of accessibility and isolation on the Milford Rd.
It also hindered emergency services which often had no idea of the scale of an emergency until they got to it.
"There are virtually no communications on the Milford Rd. When I was speaking to Dr Richard Macharg [who attended the 2002 incident] ... he said 'We didn't know what we were going to. We heard there had been a fire, but we didn't know whether there were 40 people badly burned, or with smoke inhalation ...'.
"This provides us with a way of categorising the emergency. On the Milford Rd there are a large number of incidents ... because we do [about] 1200 trips per year, we're usually some of the first on the scene.
"This [technology] is a way of providing our staff a back-up to help people out," Mr Osborne said.
The Trac Plus worked like a personal locator beacon and showed up "like a Navman".
The signal was being transmitted every five minutes and when the signal stopped, "instead of having to send a chopper", the driver of the coach could send a text message via Trac Plus to let those monitoring the service know the reason for stopping, for example, assisting with a car breakdown.
The software had been created by Dunedin company Global Ltd, using componentry from the United States, Mr Osborne said.
It was also being used in Australia and within the military.
The cost of the system was not cheap. Mr Osborne said a satellite phone could cost between $1200 and $1400, with each unit costing "about four times that".
Daily running costs included the price of reports (the system was set to track the Trac Plus at five-minute intervals), and each tracking cost US8c, with emergency messages extra.
