They are planning to erect checkpoints on all the main routes into the city if it is in danger of being overwhelmed.
More than 250,000 people are expected to descend on the capital for the Make Poverty History March next Saturday and the Live 8 concert at Murrayfield four days later.
With air, rail and bus options expected to be overwhelmed, there are fears that the main roads leading to Edinburgh will be swamped, with congestion potentially spreading back to the border with England.
In the capital, Princes Street will remain closed for 33 hours from Friday evening until Sunday morning and there will be restrictions on main roads along the march route as well as on a host of feeder roads.
There are also concerns about a planned anarchist event called the Carnival for Full Enjoyment on July 4 during which, it is feared, the city’s financial institutions will be targeted.
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Mobile electronic signs will be positioned on the A1 and the M6, the major routes from England into Scotland, and on the M8, the major arterial route between Glasgow and Edinburgh. Bulletins on national and local radio will also be used warning travellers to turn back.
If the advice is ignored police will block trunk roads and minor roads into Edinburgh.
The measure is often used at events such as football matches but usually at the request of the local authority. Police forces rarely take the decision to use the tactic.
“If it appears there could an impact on public safety, we can stop them,” said Chief Superintendent Brian Powrie, head of G8 policing.