Garrett Emmerson, who stood down as CEO last month, told Nick Ferrari that problems had arisen due to the speed with which the traffic-reduction measures had been introduced during the pandemic.
However he said they were “necessary” and praised councils for being responsive when the London Ambulance Service raised issues with certain LTNs.
Mr Emmerson was asked by Ferrari if “these could or might have cost lives?”
He replied: “Can you say that definitely, I don’t know.
“Have they delayed responses? Yes, I think in certain situations they have delayed responses.
“They had to be put in very quickly.
“They were put in in response to a massive change in the way we wanted people to live and work their lives.
“At the time, we were saying to people, don’t use public transport, walk and cycle, work from home, and you need space to do that and to do that safely.
“They were necessary, and they were put in incredibly quickly.
“We worked as closely as we could with all of the boroughs, and TfL were very helpful with that as they did a lot of the coordination.
“I have to also say, in most cases wherever we raised issues or problems with boroughs they were very responsive to doing something about it, taking things out.”
However he said paramedics would say to him: “I can show you specific instances where I have been delayed.”
Mr Emmerson continued: “One of the bigger challenges is, it is alright if you know the area, but our crews work all across London.
“Going into an area of London which they know less well, and relying on satellite navigation that inevitably is not quite up to date as some new restriction has gone in, is where the problems occur.”
The introduction of LTNs during the pandemic has been a source of controversy across London.
Filters, enforced with as plant pots or CCTV cameras, are used to stop cars going down residential roads.
Fans say that they improve air quality and allow children to walk and cycle to school safely, with less traffic on the streets.
While opponents say they cause delays on main roads and create problems for emergency services.
Ealing Council recently ripped out all its LTNs following a referendum.
In the east London borough last year, CCTV cameras and planters were vandalised.