Heavy goods vehicles (HGVs) must now be fitted with side guards to prevent cyclists being dragged underneath.
HGVs must also be fitted with a certain type of mirror to give drivers a better view of cyclists and pedestrians.
But hauliers criticised the move as a “blunt regulatory tool” and said more should be done to target a minority of rule-breakers on London’s roads.
Mayor Boris Johnson said the scheme was a “life-saver”.
Each breach of the ban carries a maximum £1,000 penalty and repeat offenders risk losing their operating licences.
The new rules, covering all roads in London except motorways, and operating 24 hours a day, were announced after a number of cyclists were killed in road crashes in London.