The scheme is one of London Mayor Boris Johnson's election pledges
Motorcyclists are now allowed to use some of London's bus lanes.
From Monday, motorcyclists will be able to ride in the restricted lanes for an 18-month trial period.
Transport for London (TfL) said it hoped the measure would cut accidents and traffic in the capital. The change will only apply to TfL bus lanes.
Pedal cyclists, who already use the lanes, have been against the scheme claiming it would not improve safety or reduce congestion.
Vulnerable road users
The scheme is one of London Mayor Boris Johnson's election pledges.
He 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. "
In June last 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".
Motorcyclists have been advised to make sure they know which lanes are open to them as the trial applies only to TfL bus lanes.
A spokeswoman said TfL manages about 44% of the bus lanes in the capital. About 90% of TfL's bus lanes are taking part in the trial.