About 300 engineering service workers, employed by the lift firm Kone, went on strike last week in a dispute over a tracker device in their cars and vans which their union, Unite, describes as an unreliable method for measuring workloads.
The union stressed that it was not against the principle of the system, known as VAMS, when used for health and safety purposes but the tracker device should not be used to verify time sheets, and site arrival and leaving times as it cannot be relied on in such circumstances.
For example, one driver was alleged have driven 1000 miles in one day — without refuelling.
Unite national officer Linda McCulloch said: "Evidence has shown the mileage recorded by VAMS for business or private use is not accurate and exaggerates the amount of mileage being completed. It is "a spy in the cab" that does not function properly, so it is understandable that our members are angry."
If employees are wrongly assessed for private mileage because of the system, this could lead to wrong deductions from wages and ultimately disciplinary situations, she warned.
There is already a framework agreement for handheld devices and Unite is looking for a similar agreement for VAMS.