Perhaps you should try some spelling variations:
"improving railway performance metrics." » "improving utility performance metrics.", "improving railway performance measures.", "improving rail performance metrics.", "improving early performance metrics."
"improving pupil performance evidence." » "improving social performance evidence.", "improving model performance evidence.", "improving judicial performance evidence.", "improving public performance evidence.", "improving civil performance evidence.", "improving audit performance evidence."

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving pupil performance evidence.") OR ("improving railway performance metrics."))~.
• Removing quotes may allow a broader search: (( improving pupil performance evidence. ) or ( improving railway performance metrics. ))~.
• Adding a wildcard symbol may retrieve word variants: (("improving pupil performance evidence.") or ("improving railway performance metrics."))*.