Vaughn's signing follows a workout he had with the Lions on Monday.
Last season, Vaughn had 30 tackles and three interceptions and a forced fumble in 16 games for the Colts with four starts
For his career, Vaughn, 25, has 124 tackles and five interceptions.
The 5-foot-11, 199-pounder went undrafted out of Ole Miss and was originally with the Denver Broncos.
After returning a kickoff and an interception for a touchdown during his two years with the Broncos, Vaughn was traded to the Colts in 2012 in exchange for fullback Chris Gronkowski.
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Aaron Wilson covers the Ravens for The Baltimore Sun.