Mr Apthorp said because there was no cellphone reception along the road, he could not call *555.
Once at Milford Sound he was told there was a form he could fill out, which would be faxed to the nearest police station at Te Anau (about two hours' drive from Milford) - but the forms had run out.
He later asked for a number to call and was given an 0800 number to use from a landline, having found the *555 number only works with cellphones.
But after being connected to the police communications call centre, he had to wait for 15 minutes on hold before he gave up, ultimately only reporting the bad driving two days later when he and his girlfriend had arrived back in Te Anau.
A Te Anau police spokeswoman said the matter was under investigation, but it was understood the rental vehicle was returned on Sunday.
Given the driver was due to leave New Zealand, it was unlikely charges would be laid.
Mr Apthorp, who now lives in the Netherlands, said he and his girlfriend had left Te Anau for Milford at 6.30am on Saturday, having been warned by his father to ''be careful for the [tourists] driving on the wrong side of the road''.
As he drove around a corner he saw a Toyota Rav4 pull out in front of him from the right side of the road.
He later asked his girlfriend to start filming the car - being driven on ''the completely wrong side of the road'' - on her mobile phone.
''I thought he was completely drunk.
''He was crossing the centre line, not really staying in any lane at all for about a minute and a-half.''
Mr Apthorp said he tried to get the driver's attention by flashing his lights, but to no effect.
It was only when the driver spotted ''keep left'' arrows painted on the road they corrected the car's position.
Mr Apthorp said he and his girlfriend took details of the vehicle and carried on to Milford Sound where the driver pulled into a lookout area.
Although he wanted to take the keys from the driver, he decided to leave that to police.
He said the only saving grace was, given the early hour, there was no traffic heading towards Te Anau.
He felt even worse after hearing about a motorcyclist killed when a vehicle apparently crossed double yellow lines near Oamaru on Sunday, he said.
Mr Apthorp said he was ''shocked'' *555 calls could not be connected along the Milford road.
''On Dutch highways, every 400m to 500m there's a landline to call emergency services, tow trucks or whatever.''
New Zealand Police Southern district communications manager Nic Barkley said police were making inquiries, into the incident, including the difficulty Mr Apthorp had in reporting the driver, but were not able to comment further yesterday.
Mr Harland said NZTA, as part of the Visiting Drivers Project, had already added rumble strips, keep left arrows, no passing lines and advisory signs to the Milford road, but more would be added.
Additionally, the agency planned to investigate options for more ''pull-off points'' along the road and more variable signage.
