Train bosses say they are “genuinely sorry” for repeated delays and faults in recent weeks.
A joint letter from Greater Anglia and Network Rail has admitted performance has slipped below expected standards.
On Wednesday, trains between Colchester and London were delayed by 40 minutes due to signalling problems.
A week earlier, a signal failure caused all trains between Colchester and Ipswich to be cancelled during the evening rush-hour.
A statement, signed by Greater Anglia managing director Jamie Burles and Network Rail regional managing director Richard Schofield, said: “We are genuinely sorry for the problems that have affected train services in recent weeks.
“Performance has been well below the standards you rightly expect and we intend to deliver.
“We are acutely aware of the frustration and inconvenience felt by our passengers when things go wrong, so we are taking urgent action to improve performance.”
The companies have pledged to respond quicker to fix infrastructure faults, upgrade signalling equipment in the Ipswich area and trial the use of stand-by buses to reduce response times when alternative transport is needed.
The statement said: “We are under no illusion as to the impact these problems have had on passengers and we are anxious to put things right.
“We believe that this targeted programme of initiatives will help restore the more consistent service we all want to see.”