Under a pay strike strikers still provide a service, but nobody has to pay. In the event of an 'active strike' strikers too continue to work and provide a service, but the employer is bound to pay a certain sum to charity.
The rail service has been dogged by industrial action in recent days. Pay strikes have been an option in the past.
Green chair Meyrem Almaci: "Nowadays organising a pay strike is rather difficult. Rail workers can be disciplined because there is no legal framework. This is why the unions usually opt for a classic strike and the travelling public is the victim."
The 'alternative strike', sometimes called the 'social strike', already exists in the US and Italy.
Meyrem Almaci: "Strikers turn up at work, but the employer receives a potent signal. For every strike day he has to pay a sum to charity. Employers have a financial incentive to end the strike."
Belgium's Spring of Discontent has encouraged talk of a legal obligation to provide a minimum service even in the event of a strike.
Meyrem Almaci: "By offering alternatives we want to exit this sterile debate with a choice between a full strike and providing a minimum service. This is a discussion that should be pursued within the trade unions. I am curious to hear their response."