Paul Newman, of Taylor Road, Southcourt, Aylesbury, was recorded doing 40mph on the gyratory in June.
He has refused to pay a £60 fine and has now begun standing close to where he was caught with a sign reading '30mph speed trappers ahead!'
But police have warned Mr Newman he could be arrested for trying to warn other motorists about potential traps and told him that if he cannot keep within the speed limit he should stop driving.
Explaining his stand, Mr Newman said: "I respect the law and understand the issue of speed and its problems, but it is out of order that the police can do this kind of thing.
"On the motorway you are given ten to 15 miles grace, I just want to see a bit of leeway when you are keeping up with the flow of traffic."
Mr Newman has been taking to the gyratory three times a week with his warning sign and says he has received hoots and waves of support from the majority of motorists.
The minimum penalty for speeding is a £60 fine and three points on your licence but Mr Newman says he would rather go to prison than suffer the humiliation of such a punishment.
"They may as well lock me up as they are treating me like a hardened criminal," he added.
Despite the threat of arrest Mr Newman plans to continue his protest.
He said: "We have lost our freedom, as soon as we step outside our front door we are being told what to do.
"The police should warn us that they are checking speed like they have to with the speed cameras. It is not fair, good citizens are being made to feel like criminals."
A spokesman for Thames Valley Police said: "Mr Newman is breaking the law as he is causing an obstruction, if he is caught then he will be dealt with accordingly.
"Thames Valley Police believe that if drivers cannot stay within the speed limits then they should give up their licence."