More than 100 road traffic officers and control room operators working for National Highways across England will launch a 48-hour strike on Tuesday.
The walkout by members of the Public and Commercial Services (PCS) is part of industrial action in a bitter dispute over pay, pensions and jobs.
Around 100,000 PCS members working in 124 government departments and other bodies have voted for strike action.
PCS general secretary Mark Serwotka said: “This strike is likely to cause problems for people returning to work after the Christmas break, and while we regret that, it’s important to remember our action could be called off today if Rishi Sunak put some money on the table for our members.”
National Highways said it has “well-rehearsed resilience plans” to ensure that the 4,500-mile strategic road network remains open and safe and is confident the industrial action will have minimal overall impact.
But it expects roads to be busy on both days and drivers are being asked to plan ahead, particularly with national rail strikes being staged at the same time.
It is advising people to check for road conditions and any congestion before embarking on a journey.
The Met Office is forecasting showers and spells of heavy rain this week.
Duncan Smith, executive director of operations at National Highways, said: “A small minority of frontline operational staff are involved in the PCS strikes, which have had minimal overall impact so far.
“We have well-rehearsed resilience plans in place to continue managing and operating our network safely.
“Millions of people rely on our roads and there is a possibility that they may be busier than usual on strike days, particularly as they fall on the first working days after the festive break when industrial action is also being staged on other transport modes.
“We’d urge drivers to plan ahead and check their vehicle is in good working condition.”
Members of PCS at National Highways have already staged three regionally focused strikes over the last month which involved some frontline operational staff – those in regional operations centres and on-road traffic officers.
The strikes on Tuesday and Wednesday coincide with a 48-hour stoppage by members of the Rail, Maritime and Transport union in the long-running rail dispute.
The PCS said the 100 figure came from the strike notice the union served to the employer.