If past conventions offer any clues, Charlotte can expect one of the largest shows of police force in the city's history: thousands of officers deployed, surveillance cameras, helicopters, barricades, street closures and metal detectors.

City Manager Curt Walton said Tuesday the city expects a $50 million federal grant to cover police expenses, and Walton expects officers will be tapped from along the mid-Atlantic during the convention. As part of an outline about the city's responsibilities, the city's host committee will pay for any expenses over the grant amount.

That would presumably come from the roughly $42 million in private money that's slated to be raised to pay for the convention. In the city's bid document released Tuesday, the host committee is also seeking $11 million in "in-kind" contributions from corporations, bringing the total amount raised to $53 million.

Terrorism fears after the 9-11 attacks and possible threats to the first African-American president have heightened worries in recent years.

In 2004, Boston's FleetCenter staged the first convention after 9-11 and authorities interrupted rail service and closed portions of a major interstate near the arena. City officials were criticized for erecting a tall black iron fence around the arena.

"I lived not far from the convention site, and there were police cars with sirens on and blockades," said Paul Bachman, director of research for the Beacon Hill Institute at Suffolk University in Boston, who has studied the impact of the Boston convention. "It looked like something you would see at a toxic spill."

The same year, New York City hosted the Republican National Convention, where about 40,000 law enforcement officers were put on duty. Inside Madison Square Garden, where the event was held, police, federal agents or private security were posted at every hallway intersection, every stairwell, even near the restrooms.

Authorities closed busy thoroughfares surrounding the arena.

Multiple streets in uptown Charlotte would probably be closed because Time Warner Cable Arena is centrally located, similar to Madison Square Garden, Bachman said.

"There will be a police perimeter (in Charlotte)," Walton said . "But it hasn't been spelled out."

In 2008, St. Paul, Minn., a city of about 290,000 residents, hosted the Republican National Convention. The city's 600-member police force grew nearly sixfold when the department recruited 3,500 officers from across Minnesota and neighboring states to assist.

On the first day of the convention, protesters threw sandbags off a bridge, smashed windows and hurled rocks, human waste and other objects at police.

Officers arrested more than 800 people during the convention, including 40 journalists covering the demonstrations.

A study group commissioned to look into what happened concluded the security response to violent protest was "slow and disjointed."

Protest demonstrations are as much a part of conventions as speeches and parties. Police have gathered intelligence about planned protests prior to recent conventions, according to the report.

In 2004, the report said, police learned about a plot by anarchists to use slingshots, molotov cocktails and bags of urine to shut down the Republican National Convention in New York. The protesters gathered at multiple locations and planned to take hotel lobbies where delegates were staying.

Police foiled the plan and the convention went on uninterrupted, the report says.

Bachman, the Boston researcher, said tight security can hurt businesses. He said Boston was forced to cancel a major ship festival.