VLADIMIR, Russia — In Russian prisons, the inmates are divided into barracks housing a hundred or so men without regard to the severity of their crimes. At night, a guard locks the door and walks away, leaving first-time offenders and people convicted of nonviolent crimes to fend for themselves in a crowd of gang members, hit men and other career criminals.

Beginning this year, however, first-time offenders may no longer have to live in fear. In the first major effort to upgrade a prison system that has changed little since Stalin established it more than 70 years ago, career criminals will be separated from the general prison population and housed in new prisons with cellblocks, rather than barracks.

President Dmitri A. Medvedev, a lawyer by training who has championed an overhaul of the justice system, is pushing the measure to first break up the culture of barracks life and then to do away with common inmate housing almost entirely.

Common barracks are unusual outside the former Soviet Union and parts of Africa, according to a London-based advocacy group, Penal Reform International. Western European and American correctional institutions typically rely on large cellblocks, with a few inmates to a cell.