London is to get more protected cycle lanes after the mayor, Boris Johnson, announced a major expansion of the scheme. The move follows a spate of road deaths and criticism from a coroner that existing lanes give cyclists a false sense of security.

Johnson, formally opening the biggest segregated stretch so far of the capital's so-called "cycle superhighway system", acknowledged that the existing network, launched in 2010 and mainly marked by just blue paint, needed improvement after a series of accidents in which riders have been crushed by lorries; including a death the previous night.

A fortnight ago coroner Mary Hassall ordered Johnson and Transport for London to explain how they planned to make the system safer after conducting inquests into the deaths of two cyclists along the east-west cycle superhighway 2 (CS2), both crushed by lorries. Separately, a man was killed on the same route on Tuesday afternoon.

Johnson said he would "take account of any comments and criticisms".

He said: "Those are interesting things the coroner said. The question is, what do we do about the blue strips? Do we need to radically review all those? I think the evidence is mixed, and what we're going to do is look at the unbounded blue strips and see if they need adjusting. I'm not saying necessarily that we're going to remove them, but we're going to see what improvements can be made to them."

A "cycle-separated" junction, where bikes have their own separate traffic light phase. Photograph: TFL

The mayor's office has announced a major revamp of the existing cycle superhighway system, including segregated lanes on the section around Aldgate, east London, where one of the CS2 fatalities, 20-year-old Philippine de Gerin-Ricard, was killed in July. The upgrades will include the installation of "cycle-separated" junctions, billed as the first of their kind in Britain, where cyclists will set off first on dedicated traffic lights before vehicle traffic is able to turn left, alleviating a major factor in serious cycling accidents in the city.

Johnson said he accepted that trucks and other large vehicles currently presented an unacceptable peril to cyclists, saying he had ridden past the scene where a rider was seriously injured by a coach only the previous evening. He said: "The big issue overall in London is the interaction between cyclists and large vehicles turning left."

In March Johnson and his cycling adviser, the former journalist Andrew Gilligan, announced a hugely ambitious plan to increase cycling in London, promising to spend around £1bn on schemes such as a completely segregated east-west bike route which would, in one section, take a lane from the Westway elevated urban motorway, as well as bike-friendly "mini-Hollands" in some outer suburbs.

On Wednesday he unveiled an expansion of this vision, including a parallel north-south largely segregated route running from Elephant and Castle in south London to King's Cross, just north of the centre.

While Johnson stressed he believed that complete bike lane segregation was impossible due to competition for road space, he said it remained the ideal: "It is clear that where we can go for good segregated schemes we should."

Asked if he saw London's future as being similar to cities such Copenhagen, where children routinely and safely cycle unaccompanied, he agreed: "That would be my dream, and I think it will happen."