Yasuo Imai, assistant director of the Hokkaido tourism bureau, said it was encouraging visitors to minimise driving and take the mass rail service which was more efficient and covered major sights.

'Hokkaido is so large that sometimes driving might become necessary. But it is much better to combine both car and rail travel to minimise the emission of carbon dioxide as far as possible,' he said.

A 143km, two-hour drive from Sapporo to the tourist spot of Furano - a destination for nature lovers and skiers - will generate about 20kg of carbon emissions from a private vehicle meeting the latest European Union emission standards.

Instead of relying on vehicles for the whole trip, Mr Imai urged visitors to use Japan Railway's joint travel packages offered with car rental companies.

Hokkaido, known for its natural scenery and skiing, had the hottest summer in 80 years last year and is struggling to reverse the effects of rising emissions.

With per capita emissions at 1.4 times the national average, the prefecture last year showed a 14.2 per cent increase above 1990 levels, a far cry from its pledge of cutting emissions 9.2 per cent below that level.

A campaign has been launched in Hokkaido to encourage its 5.7 million citizens to cut emissions before the G8 Summit to be held at its hot springs resort in Lake Toya in July.

Barry Mak Lui-ming, assistant professor from the School of Hotel and Tourism Management at Polytechnic University, said on top of solo travel, more tourists preferred the comfort and flexibility of cars over the rigidity of rail schedules and coach tours. But he said the dilemma of developing tourism and limiting the impact on the environment was difficult to resolve, and both tourists and tour agencies had yet to become more sensitive towards sustainable tourism.

'There is always a conflict between environmental protection and tourism. Unless you choose to stay at home, you are bound to create additional effects in travelling, whether you are flying in a plane or driving a car.'