The Association of Chief Police Officers (ACPO) in Scotland issued a memo Tuesday recommending that VASCAR not be used to issue speeding tickets to motorists. Although the "Vehicle Average Speed Computer and Recorder" is a thirty-five-year-old technology and has been replaced in some areas by radar and laser speed guns, it is still commonly used in the UK and the US.

"Until such time that the matter has been fully investigated, a memo has been sent to officers asking them to use alternative speed detection equipment," Strathclyde Police Chief Inspector Andy Orr told the Aberdeen Press and Journal newspaper.

VASCAR estimates speed by calculating the amount of time it takes for a vehicle to pass a given distance. The police officer operating the machine flips a switch when a vehicle passes a given point and then flips it again when the vehicle passes a second point. The machine then displays a speed on a small readout. Because the device appeared to depend more upon the skill of the operator to produce a reliable estimate, UK police authorities never required Home Office Approval or accuracy testing for the device. Instead, the VASCAR manufacturer insisted that the "quartz crystal" performed a self-test allowing the device to establish itself as an accurate instrument for measuring speed.

That did not turn out to be the case for UK officials who recently uncovered reliability problems while working to integrate the speed detector with new digital radios and automated number plate recognition (ANPR) systems. The same officials had already known about the possibility for radio frequency interference. A 2002 ACPO test registered interference any time a radio or cell phone was used within six-and-a-half feet of the VASCAR machine.

"There is a potential risk of interference to Traffic Law Enforcement Devices (TLED) such as VASCAR from Airwave Radios and GSM phones," a Devon and Cornwall Constabulary memo dated August 19, 2008 explained. "Officers should not operate a TLED from within a vehicle in the presence of a GSM phone or Airwave radio that is switched on, unless a 'Transmit Inhibit' system has been enabled. Failure to do so may compromise the integrity of any relevant prosecutions."

Now Scottish officials fear the possibility that lawyers will seize upon the unreliability of the technology to undermine past prosecutions and force refunds.