Protests are planned at 40 stations across the UK.
"The privatised rail companies have been allowed by the government to hike fares while providing a poor service on many routes".
"The number of season ticket journeys is falling and it's falling out of the reach for many, many people".
Labour accused Mr Grayling of "going into hiding" rather than defending the rise tied to last July's Retail Price Index (RPI) measure of inflation, which will see fares rise by 3.4 per cent on average, and season tickets going up by 3.6 per cent.
He said: "They say that 97 per cent of the increase goes back into rail services but you are still made to stand up for most journeys, you have little chance of getting a seat".
"Alongside investment from the public and private sectors, money from fares is underpinning the railway's long-term plan to change and improve".
"Rail travellers, who are seeing their wages lag far behind this fare increase, are being asked to take another hit to their incomes to pay for expensive and often unreliable trains".
This will ensure it is known how best to make use of existing trackside infrastructure and utilise Network Rail assets, as well as testing suitable track-to-train radio systems to deliver services to passengers under real-life conditions.
The British government sets regulated rail fares and it was announced in summer 2017 that tickets would increase by 3.6 percent this month. "Labour will bring our railways back into public ownership so they work for the many, not the few".
"Commuters have repeatedly been told that higher fares are necessary to fund investment, but promised investment has been cancelled and essential works have been delayed by years".
RMT general secretary Mick Cash said that while revenues for ScotRail operator Abellio would increase, rail travel is "becoming increasingly unaffordable for many".
"But it's also because passengers pay for the bulk of the running costs, despite the obvious economic and social benefits to the whole country from having a well-used rail network".
"Our members will be protesting today to say it is time to cut our fares not our staff and for a publicly owned railway where every penny of passenger revenue goes to improving services". This means improving connections on Britain's railways now, and making sure they are fit for the future.