The number of people speeding increased in a county where speed cameras were deactivated.
Oxfordshire's speed cameras were switched off because of budget cuts, but radar equipment was left in some locations.
Readings taken over five days found the number of drivers speeding increased by up to 88%, a rise described by Thames Valley's Safer Road Partnership as potentially "very worrying".
The radar units were set to record speeds of over 35mph in 30mph zones, though there is no longer a camera in the box to record the motorist's details.
The partnership recorded readings from two sites, with one on Oxford's Watlington Road detecting 62 offences - a rise of 88% compared to the 33 offences they expected to see there over five days.
A speed camera on the A44 in Woodstock detected 110 offences, where 93 offences would have been expected when compared with past data - a rise of 18.3%.
Dan Campsall, of the partnership, said: "These are very limited results from just two locations and a few days worth of data. However, if this is a trend that grows across Oxfordshire it is very worrying indeed.
"Evidence shows that just small changes in speed can significantly affect the risk of road users and the severity of crashes. A rapid increase in speeds across a whole county could mean many more road casualties."
Cameras in Oxfordshire were deactivated at the end of July when the county council withdrew £600,000 in funding.
Insp Paul Winks, from Thames Valley Police, told BBC Online: "It clearly means switching off the camera has given a green light to a small number of people to break the law.
"The consequence is more death and more death is unacceptable."Reuse content