The Road Races (Amendment) Bill was introduced by Transport Minister Danny Kennedy in response to issues like the North West 200 being washed out by heavy rain in two of the last three years.
From next year, promoters will be able to use up to two contingency days in relation to their race dates - which must be one of the two days immediately before or after a race or practice date.
The changes have been fast-tracked to ensure that the 2014 season can benefit.
"Every year, many thousands of people attend car and motorcycle road racing events across Northern Ireland. Motorsport significantly benefits our economy, particularly in terms of tourism and support for local businesses," Mr Kennedy said.
"I believe this Bill will add much to the rich and proud motor racing heritage enjoyed in Northern Ireland and it will help to protect our flagship road racing events in the future."
The development has been welcomed by the chairman of the group which took the lead in seeking the changes from the Department for Regional Development on behalf of NI motorsport.
Alan Drysdale, from 2&4 Wheel Motorsport Steering Group Ltd, said that the approval of the Bill "clearly demonstrates the willingness by the Minister, his officials and the Assembly to find a way to introduce much needed flexibility".
He added: "2&4 will now work with the road race promoters to assist them to develop proposals that fully satisfy the Department's requirements in relation to the implementation of a contingency day, particularly when the contingency day may be a Sunday."
According to the Department for Regional Development, the Bill does not affect cycle racing on roads and will have no impact on the Giro d'Italia visiting Northern Ireland next year.