TO GO WITH: Indonesia-Japan-economy-business-auto,FOCUS by Alvin Soedarjo An Indonesian family ride on a Honda motorcycle in Jakarta on September 24, 2011. Unreliable public transport, congested roads and a booming middle class make populous Indonesia one of the world's largest motorcycle markets, and Japan's Honda Motor wants a bigger slice of the pie. AFP PHOTO / Bay ISMOYO

Indonesia is the world's most populous Muslim country but, until recently, it was home to a liberal form of Islam that suited the Indonesians' laid-back, easy-going lifestyle and flourished under one of South-East Asia's most successful democratic governments.

Like most South-East Asian countries, it's also home to hundreds of thousands of mopeds and light motorcycles, which are used to move anything from kitchen units to entire families.

In 2001, however, the more militant northern province of Aceh asked for, and was granted, an increased measure of autonomy. Since then the provincial government has begun instituting sharia law, including the stoning of adulterers, flogging homosexuals and a ban on women wearing tight trousers.

Now the local government of Lhokseumawe, at the northern tip of the island of Sumatra, has passed a regulation prohibiting women pillions on motorcycles from sitting astride behind a male rider, describing the position as "improper".

Mayor Suaidi Yahya said that under the new law, women would have to sit 'side-saddle' with their legs dangling off to one side.

"We implement Islamic law here."

"Women sitting on motorbikes must not sit astride because it will provoke the male driver. It's also to protect women from an undesirable condition."

"When you see a woman straddle, she looks like a man. But if she sits side-saddle, she looks like a woman," Suaidi said.

Now, apart from the danger that such an unbalanced weight distribution presents to both rider and pillion, there is also the question of the thousands of Acehnese women who ride their own motorcycles, since they need both feet on the footpegs to control their bikes.

Here, apparently, sanity has prevailed in the case of women riders, however, who will still be allowed to ride astride, provided thety are dressed "in a Muslim way", Yahya said.

"Once it has become a by-law, automatically there will be sanctions if it is not obeyed."

Not all Indonesian Muslims agree, however. Activist Ulil Abshar Abdalla said: "How to ride a motorbike is not regulated in Sharia. There is no mention of it in the Koran.

"In a democratic country, what is claimed to be Sharia must be assessed by the public's common sense.