The scheme is one of the mayor's manifesto pledges
Motorcycles will be allowed to use the majority of the capital's bus lanes, London Mayor Boris Johnson has said.
From 5 January, motorcyclists will able to ride in the lanes for an 18-month trial period.
Transport for London (TfL) said it hoped the measure would cut accident rates and traffic in the capital.
Pedal cyclists, who already use the lanes, have been against the proposals claiming it would not improve safety or reduce congestion.
The change will only apply to TfL bus lanes.
Motorcyclists have been advised to make sure they know which lanes are open to them.
Mr Johnson, said: "I have long been staggered that while motorcyclists can use bus lanes in many other cities and some of our boroughs they were not allowed to use the TfL routes that criss-cross the capital.
"One of the ways we can ease congestion is by encouraging more people to get on their bike, whether pedal or powered, and I believe they should be able to share our bus lanes successfully and safely. "
The idea was one of Mr Johnson's manifesto pledges, and in June this year the London Cycling Campaign (LCC) presented the mayor with a 3,000-name petition asking him to reconsider the plans.
In a letter to the mayor, LCC's chief executive Koy Thomson said: "While we would support measures to make motorcycling safer, such as a 20mph speed limit, there is no clear environmental, safety or congestion reason for allowing motorcycles into bus lanes."
Jeff Stone, of the British Motorcyclists Federation (BMF), said allowing motorcycles in bus lanes would make it safer "for all vulnerable road users".
He said many cyclists were also motorbike riders, but some in the cycling community were "scaremongering" believing they had "a devout right to use bus lanes and that nobody else should use them as well".