Workers from the Driving and Vehicle Licensing Agency in Wales will be staging a 24-hour strike today in dispute over closures and job losses.
Members of the Public and Commercial Services union at 39 local and 10 enforcement offices in England, Scotland and Wales will take part in the industrial action. In Wales, the offices facing closure are Bangor, Cardiff and Swansea.
The union has delivered a 72,000 name petition opposing the closures, to the Department for Transport, saying it was the largest paper petition it had ever organised.
A union spokesman said: "We're very concerned about the lack of awareness among people that the offices are set to close or even that a consultation has been carried out."
DVLA said it could not guarantee a business-as-usual service because of the strike and asked people to avoid travelling to any DVLA office today.
Contact centres will be operating a reduced service and callers were warned to expect longer waiting times.
The organisation suggested conducting transactions by other means such as electronically or via the Post Office.