NEW YORK — The New York City agency that oversees jails outlined on Friday its proposed changes to the rules governing the nation's second-largest jail system, including the creation of severely restrictive housing units for inmates at Rikers Island who are deemed the most dangerous.

The proposal also adjusts the rules for putting inmates in solitary confinement, including a recommendation that inmates age 21 and younger be exempt from the punishment unless they've been accused of violence while in jail.

The Board of Correction will vote Tuesday at a public meeting to update the minimum standards for inmates, which carry the full force of law. The nine-member board is expected to approve the rule change.

The $14.8 million "enhanced supervision housing" units, proposed in response to surging levels of violence on Rikers Island, would allow wardens to lock 250 inmates in their cells up to 17 hours a day, restrict their movements and access to the law library, monitor their mail and limit contact visits.

Infractions that would land inmates in the units include seriously injuring other inmates or staff, jail gang violence and possession of small blades.

The proposal also calls for 40 hours of training for guards to recognize mental health disorders and to learn how to deescalate tense situations.

But inmate advocates and others have complained the proposed housing area would open without specific plans for therapy, programming and other activities designed to address the root causes of violence and limit idle time — something the rules call for to be implemented by July 2015.

At a public hearing last month, the former head of mental health services in city jails testified that previous attempts to create special housing units for troublesome inmates that similarly claimed would provide therapeutic services ultimately turned into restrictive, punitive holding pens. Inmate advocates and civil rights groups further argued the proposed units would infringe on inmate rights.

The rule prohibits all inmates ages 18-to-21 — except those who commit serious, violent infractions — from being placed in either solitary or the enhanced supervision housing units. Inmates would be entitled to a placement hearing after being sent to an "enhanced supervision unit."

The proposed rule also would codify into the minimum standards reforms to solitary confinement — called punitive segregation in New York but commonly referred to as "The Bing."

Those changes mirror policy changes Mayor Bill de Blasio and his jails commissioner, Joseph Ponte, already have said they would implement. They include eliminating the practice of putting inmates in solitary for infractions earned in previous incarcerations, ending the practice as punishment for minor offenses, stopping it altogether for inmates ages 18-21 except for those accused of violence, exempting the seriously mentally ill from solitary and capping solitary stints to 30 days among other changes. The 16- and 17-year-old inmates also are prohibited from being placed in solitary.

After a scathing review by federal prosecutors investigating conditions at Rikers for teenage inmates released last August, Ponte separated 16- and 17-year-old inmates and announced he'd stop putting them in solitary confinement. The rule requires that by October, inmates ages 18-21 be housed together and by August, corrections officials provide the board with plans for age-appropriate activities for them.

The board announced in September 2013 that it would investigate how and when 23-hour confinement is doled out to inmates who break jailhouse rules with the aim of codifying reforms that would vastly limit the practice.

But reforming solitary seemed to take a backseat after "enhanced supervision housing" was proposed last fall by correction officials who have claimed it's necessary to isolate the small number of inmates behind a disproportionate amount of jail violence before reform can take place.