A University of Alabama at Birmingham (UAB) Department of Justice Sciences study published in The British Journal of Criminology, found that “rock rentals,” where addicts loaned their cars for several hours or days in exchange for drugs, were becoming more prevalent FOX News reports.

Criminologists reported that 19 out of 30 prisoners they interviewed in Louisiana admitted to renting cars belonging to addicts in exchange for drugs. Some of the borrowers admitted to stealing cars belonging to addicts while most said they honored all rental agreements to protect future transactions.

Most crack cocaine addicts reported being selective, renting only to family members and friends who sold drugs or to trusted dealers; they also said that renting was a cheaper alternative to cash payments and protected them from violence and humiliation from drug dealers, according to researchers, according to the study.

FOX News reports that the growing popularity of “rock rentals” is in part because crack cocaine is cheap to produce and the distribution of the drug is in reach of street-savvy youths who may not own cars.