Emergency services will be permitted to use the Olympic Lanes
Road lanes reserved for Olympic athletes and officials during the 2012 Games could slow ambulances and increase congestion, police have said.
Some London road lanes will be designated for athletes and VIPs to ensure they arrive at events on time.
The Metropolitan Police has told a consultation the lanes could cause "significant increases" in congestion.
A Department for Transport spokesman said emergency vehicles would be permitted to use the lanes.
A condition of hosting the Games is that the host city must designate a network of roads linking the venues, known as an Olympic Route Network.
The busiest sections of London's network are likely to contain dedicated "Olympic Lanes" reserved for accredited Games vehicles only.
The Met and London Ambulance Service told a consultation on the plan the Olympic Lanes could have "significant impact" on people living nearby.
There is currently little scope for Olympic Lanes in London and too little work has been done in preparation for them, the Met added.
Police were also concerned the plan was based on an assumption there was less traffic in London during the summer, a period when traffic is actually heavier on some of the city's roads.
The Department for Transport said emergency services would be able to use Olympic Lanes in an emergency during the Games, being staged from 27 July to 12 August 2012.
The spokesman added: "As the emergency services recognised in their responses, designation is the very first step in implementing the Olympic Route Network.
"The Olympic Delivery Authority (ODA) is working with the emergency services and authorities to make sure that we are able to resolve any issues in good time."
Hugh Sumner, the ODA's director of transport, said its priority was "to ensure that emergency services are able to operate as usual during the Games".
He added: "We have been working closely with the emergency services since we began consultation on the Olympic Route Network and will continue to do so to ensure any issues are resolved in good time."
The Met and London Ambulance Service would not comment further.