The decision to allow women to drive in Saudi Arabia is a rare good-news headline from the Middle East. King Salman has said it is to take effect from June 2018; the delay seems intended to get conservatives accustomed to a highly visible social change and deal with the practicalities of training female driving instructors and traffic police.

Why has this change happened now, after so long? It is partly the result of top-down factors, as a new crown prince ushers in a new style of politics. It also reflects changes coming from deep within a society that may be highly religious, but is also very young and faces a new economic future.

Credit for this decision will be given to the new Crown Prince, Mohammed bin Salman. At 32, he styles himself as a moderniser. Letting women drive does more to change Saudi Arabia's image than any other single policy announcement could, and will also burnish his personal image as an agent of change.

Social attitudes are divided

But it is not just an issue of a leader with a different attitude to women. For years, most senior Saudi princes, including the late King Abdullah, were assumed to have no personal or ideological problem with women driving. The reason they gave for not letting women drive was that "society was against it".

In fact, social attitudes are divided over whether women should drive - and over a host of other issues to do with religion and society. This is not a division between young and old, or men and women, but between different visions for national and Islamic identity.

The ban on women driving was not a case of the Saudi government suddenly being democratic about its social regulations. Rather, it was a concession to a particular section of society: the influential, socially conservative religious clerics.

The Saud family has always governed with the support of clerics, but some of them have also been critics of the government. The driving ban was an attempt to appease this important constituency and dissuade them from being a potential source of opposition.

Ending it signals that the clerics no longer have the same role to play in Saudi policy. The old model of ruling was to rely on oil and clerics. Prince Mohammed is trying to build a new model based on nationalism, economic development and the sense that the Saud family provide the security and stability missing in too many other Arab states.

But there are still risks of a backlash against him, especially given the state of the economy, which is suffering from the drop in oil prices since 2014. And partly for that reason, Prince Mohammed's focus on economic and social liberalisation is not accompanied with political liberalisation.

Quite the opposite: several influential clerics and writers have been arrested in recent weeks in a sweeping crackdown, seemingly triggered by accusations that they sympathised with Qatar.

The fact, that even high-profile clerics can be arrested means most Islamists and conservatives will be less likely to speak out - whether over the driving ban, foreign policy or economic austerity.

Saudi Arabia's women activists have campaigned for years to be allowed to drive. A civil disobedience campaign in the 1990s saw many women arrested at a time when the government was fearful of Islamist opposition.

During the Arab Spring, a new #Women2Drive campaign rose up through social media with activists such as Manal al-Sharif. She filmed herself driving a car and posted it on YouTube. Afterwards, she was arrested, briefly detained, then sacked, harassed and subjected to death threats before she left Saudi Arabia.

Brave women's driving activists were the tip of the iceberg. There is a broader mega-trend of Saudi women's economic empowerment, rooted in years of investment in women's education under King Abdullah, including scholarships to study around the world.

The new generation of women includes both liberals and conservatives, but they are growing up with different economic expectations. Education enables new opportunities, while at the same time, the rising cost of living and pubic sector austerity means many middle-class families need both parents to work in order to maintain their living standards.

Working outside the home requires transport, and Saudi Arabia has virtually no public transport. The absurdities of having to pay men to drive you to work were recently highlighted in the film Wajda, directed by a Saudi woman. So for many women, it is simply a practical issue.

But the law will have a mixed impact as conservative husbands and fathers will still try to forbid their wives and daughters from driving. Currently, the guardianship system and patriarchal culture mean that women's opportunities and choices depend heavily on those of the men in their family.

This is why the role of Saudi women is much more diverse and heterogeneous than is commonly assumed. Women with liberal families might study abroad and become a CEO, while another woman could be prevented from leaving the house altogether.

For this reason, Saudi women activists are increasingly focused on tackling the guardianship system as the next step. Manal al-Sharif tweeted on Tuesday: "#Women2Drive done #IamMyOwnGuardian in progress."