A limited timetable between Glasgow and Edinburgh was due to operate in and around the central belt, but it is expected that no trains will run north of Perth during the stoppages because the larger number of smaller signal boxes makes the area harder to cover using contingency staff.
First ScotRail said customers should check its website for revised timetables.
Speaking to BBC Scotland, two striking signal workers in Motherwell said they did not understand why the dispute had escalated to the stage of industrial action.
One said: "All the management have to say is that if we want to change our rosters, then we agree to it mutually - that's all they need to do."
The other added: "We didn't expect to be out here on strike for such a silly matter. We're all baffled why Network Rail aren't sorting it. We've not had any reasons from them why they can't sort this out."
Bob Crow, general secretary of the RMT, told BBC Radio's Good Morning Scotland programme: "The fact is, how can you have a balanced lifestyle, when you get told on the Thursday that, for example, you'll get next Tuesday off and you've got childcare arrangements, social arrangements, then you're told on the Monday that we can now change your roster and you've now got to come to work.
"It's totally unacceptable in 2008."
Advertisement
Thousands of train travellers are having their journeys disrupted due to a walkout by rail signal staff.
Mr Crow said the union would be available for talks again after midday on Wednesday and dismissed Network Rail claims that the RMT had misrepresented the issues to staff.
But Network Rail route director David Simpson told BBC Radio Scotland's Good Morning Scotland programme: "There's a fundamental difference between us and that's whether or not vital safety assessments should be voluntary.
"RMT's view is that they should be, we're saying safety is critical, there's no compromise in that and we have to be able to roster those without them being voluntary."
Mr Simpson also claimed RMT members had not voted to strike on the safety assessment and did not understand why union representatives had made it such an issue.
Glasgow Chamber of Commece chief executive Richard Cairns said: "There will be serious disruption to business as staff struggles to get to work and working time is lost. In the current economic climate, this strike is particularly unhelpful."
A spokesman for Network Rail said the RMT had been asked to take part in further talks on Wednesday ahead of Thursday's planned strike.
Bookmark with:
What are these?