Here’s where you can download the UI mod:
https://dl.dropboxusercontent.com/u/77888280/TF%20Mod/LargeUI_mod.zip
Here’s some details from the developer; note that this is a MOD and can therefore alter the game in unexpected ways.
INSTALLING THE MOD
Make a backup of your Train Fever res/texture/ui folder (and subfolders) if you want.
Drop the “res” folder in this Zip archive to your Train Fever root folder, usuallynamed “Train Fever”. Overwrite all files when prompted.
TO UNINSTALL THE MOD
Select “Verify integrity of game cache…” from the Steam client to get a fresh TFcopy or just move back your backup ui folder.
