At a public inquiry in Edinburgh, Joan Aitkin, traffic commissioner for Scotland, heard evidence from the DVSA that the first device was found in November 2016. Subsequent investigations revealed a second device in another vehicle, which had been disconnected.
There was doubt over when and where the devices had been fitted, and the vehicles had not been in use while the devices were in place.
The regulator stopped short of revoking the licence, saying: “There is a very dark cloud of suspicion but significantly for the operator there was no use of the equipment and no criminative or circumstantial evidence which would point to such use being likely.”
The curtailment order against J&G Riddell will take effect on 19 October.
The regulator also warned the operator and director Gordon Riddell as to their repute. Transport manager John Riddell was also given a warning and told he must attend a refresher course within six months.