Perhaps you should try some spelling variations:
"improving road performance metrics." » "improving road performance measures.", "improving board performance metrics.", "improving good performance metrics.", "improving bond performance metrics.", "improving food performance metrics.", "improving rural performance metrics."
"improving road performance series." » "improving road performance studies.", "improving road performance size.", "improving board performance series.", "improving good performance series.", "improving bond performance series.", "improving food performance series.", "improving rural performance series."

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• Performing a fuzzy search may retrieve terms with similar spellings: (("improving road performance series.") or ("improving road performance metrics."))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (("improving road performance series.") OR ("improving road performance metrics.")).
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