This type of check, commonly known as the ‘follow check’
has been used by police forces for a number of years and is
readily accepted by the courts and motoring public alike. If
the speedometer is used to support the suspicion of the officer
then it must be tested as detailed below.
Means of Check
A road policing vehicle must be fitted with a certified calibrated
speedometer regularly tested in accordance with Force instructions.
The checking vehicle should be positioned to the rear of the
suspected offending vehicle so as to maintain, throughout the
check, an even distance between the vehicles. Speedometer readings
should be taken throughout, preferably related to readily identifiable
points passed.
Minimum Distance
2/10 of a mile, is the minimum distance recommended by ACPO
for such a check.
Speedometer Accuracy
The patrol vehicle speedometer should be checked for accuracy
at the end of a tour of duty after detection of an offending
vehicle. Speedometer accuracy can be checked using: a certified
measured distance with certified stopwatch or chronometer; or
a rolling road type device; or against another Type-Approved
device NOT fitted to the vehicle, e.g. laser or radar equipment.
Measured Distance
Each element of the checking procedure should withstand challenge,
and where certified distances are used these should be laid
to engineering standard. The evidence of the person creating
a measured distance should be available.