Morning train services between St Albans and London will be leaving two minutes earlier from Monday due to slippery leaves on the track.
Two services running through St Albans and Harpenden will be affected by the changes.
A first train will now arrive at Harpenden at 6.18am and St Albans City Station at 6.24am.
The second will come into Harpenden at 6.38am.
The changes will stay in place until Friday, December 7.
Fallen leaves on the track are not thought to be dangerous but they reduce the speed that trains can speed up and slow down.
A spokesman for First Capital Connect said: "Extending a couple of morning journey times by a few minutes will allow us to deliver a more consistent service through the autumn."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here