More crack, cocaine users are renting their cars in exchange for drugs, according to a new criminology study.

In their study, published in The British Journal of Criminology, criminologists at the University of Alabama at Birmingham (UAB) Department of Justice Sciences found that “rock rentals,” where addicts loaned their cars for three to four hours in exchange for drugs, even overnight or over a weekend, was becoming more prevalent.

Criminologists interviewed 30 incarcerated people in two prisons in Louisiana. Nineteen of them 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.

Researchers then interviewed 27 crack cocaine addicts who were not incarcerated to better understand how rock rentals were conducted. Most addicts reported being selective, renting only to family members and friends who sold drugs or to trusted dealers. Addicts also said that renting was a cheaper alternative to cash payments and protected them from violence and humiliation from drug dealers, according to researchers.

“The prevalence of the practice was acknowledged in interviews with both police and inmates who had not participated in them [rock rentals],” the researchers said.

One reason for the growing popularity of rock rentals is that crack cocaine is cheap to produce, according to researchers. according to researchers, and the distribution of crack cocaine is in reach of street-savvy youths who may not own cars.

Future studies are planned to examine the effects of rock rental on police policies as well as on the study of addiction and behaviors related to addiction.