OAKLAND — As police geared up for a fourth night of protests on Monday, Oakland Mayor Libby Schaaf said a new tactic of directing demonstrators off the streets and onto sidewalks and plazas is cutting down on the vandalism that often follows them.

Oakland Police had a “contingency plan” in anticipation of protests Monday night, said Officer J. Moore Protesters were nowhere to be found, but officers were out there, at 8:15 p.m. at Frank H. Ogawa Plaza.

“We’re basically in holding mode, waiting for them to show up,” Moore said Monday night.

IndyBay.org, an online Bay Area news forum, posted about a “#BreaktheCurfew” protest scheduled from 9 to 11 p.m. Monday starting at Frank H. Ogawa Plaza.

Sunday night police arrested four and cited 19 others in downtown Oakland during a protest against the new tactic — the second such gathering in as many days.

Officers watched closely Sunday night as about 150 marched several blocks back and forth on Broadway downtown for about 40 minutes. A smaller group of about 20 then decided to march in the street north on 14th Street. Police told them to move to the sidewalk, which they did, and they headed for Frank H. Ogawa Plaza where the protest ended at 10 p.m., police said. There were no reports of injury or vandalism.

A night earlier, dozens of protesters were arrested or cited for ignoring police orders to disperse during a similar protest against the new protest rules.

Oakland has hosted rallies in the streets for years, but Schaaf said the new tactic, which is contained in existing policy, is needed to combat damage to property and violence.

She said the change was made to prevent vandalism and violence in the wake of the May Day protests earlier this month, when many businesses on Auto Row were significantly damaged by protesters who broke off from a larger crowd to cause mischief.

“The real goal is to get them on the sidewalk or to public plazas like Frank Ogawa Plaza where they can continue peacefully and there is no danger of conflicts with people in cars,” Schaaf said Monday.

Schaaf said protesters who get a permit from the police department can walk in the streets and the police will block traffic for them. But many of the protests have occurred without a permit. When the vandalism starts, she said police are allowed to declare an unlawful assembly and “that requires everyone to disperse, including the peaceful protesters.”

She said she wanted to be clear that the change is not meant to be a curfew and that the city is on solid legal ground.

“It’s these nighttime protests where vandals have taken the opportunity to do damage to our city,” Schaaf said. “We’re trying to find other ways for people to express themselves in a way that is much less likely to cause vandalism.”

When asked how the new tactic decreases vandalism, Schaaf did not answer directly.

“Our intention is that this practice of encouraging demonstrations to take place on the sidewalks will allow them to focus their attention on the content, which is really important, and less on the collateral damage.”

Businesses have sustained heavy damage during protests arising from the deaths of unarmed black men in police custody in Ferguson, Missouri, and elsewhere over the last two years.

Tensions rose anew on Thursday when protesters marched in honor of black women killed by police across the nation. But organizers said they were surprised when Oakland police pushed them off the streets and onto the sidewalks, citing the mayor’s new policy. No one was arrested Thursday.

Organizers then called for another protest Saturday to demonstrate against the new policy.

“You can’t run roughshod over people because they’re protesting your oppression,” said Cat Brooks, an organizer of both protests. “You can’t push us off the streets.”

Schaaf said the new tactic has been successful so far because in the last three protests, including Sunday night, no vandalism occurred. Rachel Lederman, a lawyer with the National Lawyers Guild who helped Oakland craft its crowd-control policies, said the new tactics appear to violate the guidelines.

“It doesn’t make any sense because saying that marches have to be on the sidewalk has absolutely no relationship to impending property damage that might occur,” Lederman said. “Obviously, that would happen on a sidewalk, not a street.”

Schaaf said she has heard and acknowledged criticism of the new tactic.

“I respect that there are a variety of feelings about this new practice,” Schaaf said. “Yes, there has been a level of anger, but I believe it is a sensible way of moving this city forward that protects our history of activism.”

Staff writer Katrina Cameron contributed to this report. Follow reporter Doug Oakley on Twitter at www.twitter.com/douglasoakley.