Train operators have dismissed suggestions of problems for commuters as a result of an overhaul of timetables and services.
Some lines have more services, while others have fewer
The shake-up came into effect on Sunday, with more trains running in some areas and fewer in others.
The Association of Train Operating Companies admitted some "teething problems", but said that on the whole the transition had worked well.
The Rail Passengers Council said it was too early to judge the changes' impact.
Train companies said the changes would mean an extra 320 passengers trains a day, bringing more frequent services to most lines at times of highest demand.
New services have been introduced in areas with rapidly growing populations, but others now have more frequent stops while some smaller stations have reduced services.
That has led some commuters complaining they are worse off under the new timetables, but operators have dismissed these as isolated examples.
ATOC spokesman John Dennis said: "There may have been teething problems in some places but nothing untoward that we're aware of.
"Some stations have fewer trains and they're the ones saying it's dreadful, but it's a matter of balancing the needs across the entire network."
He said it was up to passengers to check the new schedules and plan accordingly.
Operators urge commuters to check the new schedules
"We've done an awful lot of advertising. If people choose to ignore that, it's not the train operators' fault.
"We'd expect people to check the timetable."
The Rail Passengers Council's Peter Biggs said: "Commuters are taking a little time to adjust. A lot of passengers may not have fully realised the impact the changes will have on their journeys.
"We do have some concerns around overcrowding and passengers who are negatively affected by the changes - as fares are likely to rise in January these passengers could be hit twice by changes in the rail industry.
"[But] because it's such a major change, it will take time to assess the long-term impact."
Some of the biggest alterations are those to services run by South West Trains, which has rescheduled all of its 1,635 trains.
Spokeswoman Simone Spinks said the company was aware of complaints from some passengers and would continue to monitor the implementation of the new timetables.
"Some people aren't happy that the trains they're used to catching are at another time or may have extra stops, but performance is our biggest issue and we think this is the best way [of improving services to passengers]", she said.
She said data from Tuesday's morning services showed almost 94% of its mainline trains and 92% of suburban trains arrived within five minutes of their scheduled time.
This was ahead of performance targets, she said.
But the Southern England RPC said since journey times were longer for some services, punctuality targets would be easier to hit.