Some Chicago businesses have told employees they can work at home Friday and next Monday because of NATO summit-related security and transportation concerns. Companies including Aon and Blue Cross Blue Shield of Illinois have told workers they would be allowed to telecommute Friday, when a major downtown protest is scheduled, and Monday, the last day of the two-day summit, the Chicago Tribune reported. Some businesses have decided to close while others have added security or taken precautions like coating glass windows in plastic film so they don\'t shatter if broken during a protest. The American Medical Association told its employees it would close the AMA\'s River North headquarters Monday because of \"transportation challenges\" related to the summit. The commuter rail service Metra isn\'t allowing most carry-on items on commuter trains, including backpacks and any bag larger than 15 inches square. Brian Tishuk, executive director of ChicagoFIRST, an organization of the city\'s major financial institutions and other companies, said those businesses will emphasize security. Some plan to hire armed guards while others have gotten pre-cut plywood to cover exposed or broken windows and many have plans to provide for employees in case they become trapped in their workplaces. \"There\'s been an emphasis on being sure they can lock down a building,\" Tishuk said.