There is no border post on the north-bound coastal road where it crosses into Aceh province on the tip of Sumatra island. But several things make it clear that you have entered Indonesia's most rebellious territory.
First there are the occasional rows of misshapen oil drums in the roadway warning drivers to slow down going past Indonesian army (TNI) and security police (BRIMOB) posts, where soldiers in bandanas casually train automatic weapons on passers-by.
Next there are the white veils worn by every female passer-by, including the long processions of giggling schoolgirls on pedicabs which clutter the verges of the highway in the early morning and late afternoon, for Aceh is a strictly Muslim province with its own religious rules and customs.
Then there are the huge letters painted on the road surface spelling out in gaily-coloured letters the word "Referendum" at every one of the scores of hamlets along the 500km route through flooded rice paddies and vast palm oil plantations to the capital, Banda Aceh. In bigger villages teenagers man their own oil-drum barriers, collecting money for Aceh's campaign for a referendum on independence from Indonesia.
Aceh, which has been fighting for an Islamic state since 1989, is in the grip of referendum fever following the success of East Timor's August poll which precipitated its break from Indonesia. It has become so all-pervasive an issue that members of the Aceh Merdeka (Free Aceh) movement and their supporters are now referred to simply as the "referendum people".
In recent weeks the campaign has generated almost daily demonstrations. In Langsa on the coast road, a mass rally which locals described as a "carnival" persuaded the normally timid East Aceh legislature, housed in a graceful old Dutch colonial building, to join the call for a referendum.
At the town's biggest mosque, where printed notices inform worshippers of a mass pro-referendum conference to be held in Banda Aceh on Monday, a teacher of Islamic oratory said: "Most of the people want a referendum to end the colonisation of Aceh by Jakarta, and they want independence, not autonomy."
Years of brutal military repression, now openly acknowledged in Indonesia, had made the population demand a poll on the East Timor model, said Dr Ismail Umar. "The people don't like the army or the police, even if they are recruited locally. They will be kind to their face but in their hearts they know that TNI and PRIMOB are the main enemy. If they show it, they will be killed."
It is not hard to find evidence of military excesses in Aceh, where almost 300 people, including many soldiers, have been killed in renewed violence since May, and an estimated 200,000 villagers driven from their homes by army raids and house-burnings reminiscent of the terror in East Timor.
Incidents of violence are commonplace. In the little town of Peureulak, 40km from Langsa, local people told me that PRIMOB police had shot dead one man and injured many others in a clash with "referendum people" just the evening before.
Police chief Bakhtiar smiled and politely refused to discuss the incident when I called into his dingy roadside office, with its two portraits of Indonesia's bemedalled top policeman, Gen Roesmanhadi, and his wife, Pertiwi, in pink suit and pearl earrings.
But he acknowledged that the violence in the countryside around had forced thousands of rural dwellers to crowd into Peureulak for protection.
I found some 400 of these poor people billeted under tarpaulin around a nearby silver-domed mosque. Once numbering 7,000, they were being looked after here, and at 11 other mosques and schools, by students from the People's Social Bureau, a non-governmental organisation.
The internally displaced people fled from their villages because they came under attack by TNI looking for Aceh Merdeka fighters, said Arifin, the local secretary of the organisation, who added: "The army destroyed our culture, and PROMOB cause the trouble. That's why people want a referendum."
Many refugees had, however, been able to return home because of a new policy by Indonesia's newly elected President, Mr Abdurrahman Wahid, who has ordered an end to the military repression and is trying persuasion to solve what he admits is the biggest single problem of his presidency.
Aceh's pro-Jakarta bureaucrats, such as Mr A.E. Aluddin, governor of the East Aceh regency, argue that not everyone wants a referendum. "It will lead to big problems and turmoil," he told me in his white-tiled Langsa office. "Aceh is different from East Timor," he said. "East Timor was the last province to join Indonesia, but Aceh is an old province. We have a shared experience with the rest of Indonesia as we fought the Dutch together, where East Timor was a Portuguese colony.
"And Aceh is Muslim like the majority in Indonesia while East Timor is Christian. It was easy to let go of East Timor. But if Aceh goes, it is a big problem for Indonesia. It is like if you cut the root off a tree, it will die."
However, even the governor acknowledged that the situation was critical and that Jakarta was to blame.
"Suharto ignored the Aceh people," he said. "Now the new president has to pay attention. Maybe some people don't want a referendum, but if the government pays no attention, they will demand a referendum, too." Referring to Mr Wahid's pre-election pledge that provinces should be able to keep three-quarters of their revenues, the governor said: "Aceh is rich in minerals and gas. If the government gives 75 to 80 per cent to the people, they will behave themselves and forget a referendum."
Aceh representatives have long complained that their resources have been unfairly exploited by Suharto and his cronies, that their special Islamic culture, arising from an earlier conversion to Islam, has been undermined and that gross breaches of human rights by the army have not met with a legal response. Added to that they are finding out now, with the end of censorship, that promises made in the past to quell rebellions were never kept.
This history of deceit may undermine confidence in Aceh in Mr Wahid's dramatic announcement on Thursday that the people here had indeed the right to a referendum. It was given after Aceh parliamentarians travelled to Jakarta to deliver an ultimatum that if a decision were not announced within a month they would hold it themselves.
"People can no longer wait," warned Mr Saifuddin Bant asyam, director of a human rights NGO in Banda Aceh. But he was sceptical of international support. "We know the principle of humanity is universal but the fact is that the international community applies that discriminately," he said. "Politics remains the decisive factor in the selection of cases."