Public transport in Dublin is likely to come under increased pressure today with the return of schools, the National Transport Authority (NTA) has warned.
It urged that public transport should only be used for essential journeys and customers should avoid peak time travel.
The NTA said reduced capacity on public transport remains in place, causing pressure on some services.
In line with the government's Level 5 plan, public transport capacity is restricted to 25pc. This has resulted in some services coming under severe pressure, with passengers being left behind in some instances.
The problem is most acute on buses early in the morning, particularly in the Dublin region.
NTA Chief Executive Anne Graham said: "The return of schools on Monday is likely to give rise to additional pressure. We are anxious to make sure that customers are aware of the situation.
"NTA is asking people to avoid travelling at peak times and only to use public transport for essential purposes.
"Nobody wants to see a situation where essential workers, such as those on the healthcare frontline, cannot get on a bus.
"People who can work from home should work from home.
"We continue to encourage people to walk or cycle where possible. Customers who have no alternative to public transport should expect their journey to take longer and plan ahead accordingly.
"Drivers and other public transport staff are working in a very challenging environment, and customers should remain respectful of them at all times.
"And of course, wear a face covering while using public transport."
Meanwhile, National Bus and Rail Union General Secretary Dermot O' Leary said: "Although the difficulties that commuters are experiencing in accessing buses because of the current 25pc capacity restrictions have been previously highlighted, it would appear that problems still obtain across a range of bus routes.
"While the Halloween Mid-term break did bring some relief with schools being closed, the reality is that those routes that serve up to nine hospitals across Dublin are still experiencing capacity difficulties, with vital frontline HSE staff being unable to access their bus to work"
"The NBRU did submit to the Oireachtas Special Committee on Covid-19 response and wrote to the then Taoiseach and other party leaders to propose that schools, colleges, retail and other general employments would have staggered opening and closing times.
"We did so in anticipation of the manifestation of the type of problems we are now witnessing.
"While both the current and former Taoiseach responded positively to our proposal, it appears that it has yet to formally considered as an actual policy."