On a good day 2000 people will hike the Tongariro Alpine Crossing - testing parking and toilet facilities to their limits.
The 20km day trip in Tongariro National Park runs between Mangatepopo, with 65 car parks, and Ketetahi, with 35. It takes in craters, blue and emerald lakes and views far and wide when the weather is fine.
Its popularity has grown steadily, to the point where 120,000 to 130,000 people make the tramp every year. The Conservation Department and Ngati Hikairo ki Tongariro iwi both have interests in keeping people safe and the environment intact.
They are reviewing use of the track, with economic, environmental and cultural matters all part of a complex mix.
Whanganui tramper Barry Hopper did the walk for the first time last week. He said the crowds were unbelievable. The club van had to park on SH46 because there was no room in the Ketetahi car park.
"The entire way it was just wall to wall people, mostly just going the one way. There were 20 or 30 people waiting to go at every toilet stop."
One of the aims of the review is to spread people out more on the track. Most want to start early, but with a walking time of five to eight hours the track can be started as late as 11am in summer.
Another is to encourage people to book with tourist operators and leave from nearby centres like Taupo, Whakapapa and National Park, rather than expecting to park their vehicles at either end.
"Tactical changes to alleviate congestion" are being put in place.
The department (DOC) has also provided a lot more toilets, with some camouflaged to blend into the landscape.
"We don't want the track to be marked with loos all the way along," senior communcations advisor Herb Christophers said.
Tongariro Expeditions owner Jared Thomas has been ferrying people into the crossing for 20 years and agreed numbers had grown steadily.
He said about a quarter are travelling independently and want to be able to park at one end of the track. DOC's idea to encourage people to use tour operators and leave from larger centres won't work for them.
He fears DOC will close the roads in to Mangatepopo and Ketetahi when all the car parks are full. The result is kilometres of cars parked along state highways.
"There's a real easy fix to all this - make the car parks bigger," he said.
DOC will not be doing that, Mr Christophers said.
"We are not about to put a bigger car park into a World Heritage Area."
At times Mr Thomas has paid people to manage car parking at Ketetahi. It benefited everybody but created "a political stoush", and he's stopped doing it. He's now thinking of working with Ngati Hikairo to create another parking area open to the public.
Providing facilities for bigger numbers of visitors costs DOC. Director-General Lou Sanson once suggested charging people for the country's nine Great Walks - $100 a time for visitors and $40 for New Zealanders.
Another option floated is a $25 conservation charge paid by visitors as they enter the country. Neither possibility has been taken up.
Under current legislation people can enter conservation land whenever they like, without being charged. They can only be charged for using facilities.
Mr Thomas said charging would be good and DOC should get the money and use it to provide facilities.
"We live in a user pays society. Every other country I have been in, tourists get charged."
Council of Outdoor Recreation Associations of New Zealand co-chairman Andi Cockroft said charging New Zealanders is not on, because they already pay for conservation through their taxes.