Two-time Olympic champion Humphries switched allegiance from Canada to the US before the start of this season.
The American pair led from the start and never relinquished top spot as they finished 0.37 seconds ahead of German duo Kim Kalicki and Kira Lipperheide.
Canadians Christine de Bruin and Kristen Bujnowski secured bronze for the second successive year, finishing 1.06s behind the gold medallists.
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The crown ensured Humphries won her third world title, after success in 2012 and 2013, and put her level with Germany's Sandra Kiriasis as the only female drivers to win three world titles.
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