Free tickets on Te Huia's train service are up for grabs for a week as the service is allowed back into central Auckland, following a ban by Waka Kotahi last month.
The Hamilton to Auckland train ran two stop signals and was forced by the transport agency to step up safety measures.
Since 11 July, Te Huia has only carried passengers as far as Papakura instead of The Strand in Parnell.
Waka Kotahi initially required KiwiRail to install the European Train Control System (ETCS) before it would be allowed to re-enter central Auckland. But KiwiRail operations executive general manager Paul Ashton said the organisation worked constructively with the transport agency on alternative safety proposals.
ETCS is a predictive system, which slows a train as it approaches a red signal.
KiwiRail has instead installed Electronic Train Protection (ETP) on Te Huia, which automatically stops the train if it passes a red signal.
Ashton said there was also be additional training for drivers.
"KiwiRail took both incidents seriously, and has worked closely with the rail regulator to resolve its concerns," he said.
"The rail network is safe and well managed, and we want to assure the public of this."
Waikato Regional councillor and Future Proof Public Transport Subcommittee deputy chair Angela Strange said the resumption of services was "incredibly exciting".
"A lot of relieved people as well, so many of our community rely on Te Huia for getting up to Auckland and also those Aucklanders wanting to come down into the Waikato as well."
Strange said passenger numbers dropped significantly, with about 100 commuters fewer on average for each service, during the ban.
The free tickets for a week was recognition of the extra hassle for commuters who had to change trains at Papakura, she said.
"It put a lot of our passengers out of pocket."
Strange said the free fares were for Hamilton passengers to Auckland and vice versa.
Te Huia is currently on a five-year contract, which is due to end in 2026.
"It [the ETCS] is obviously going to be a condition for the trial of Te Huia to continue beyond 2026 so that's going to be a key consideration for all parties," said Ashton.
Strange said the hope was that ETCS would be installed on Te Huia after the completion of the City Rail Link in Auckland.
The first service on 7 August will depart from Hamilton after 6am and arrive in Parnell just before 9am.