Organizers discouraging spectators, volunteers from congregating at aid stations. Cars will be towed starting at 1 a.m. Sunday.
As the first major U.S. marathon since the Boston bombings steps off Sunday, Chicago Mayor Rahm Emanuel said the city feels prepared for the race and most importantly runners won't be deterred by fear.
"The world will watch the endurance of the human spirit to persevere," Emanuel said Thursday at the marathon's kick-off press conference. "While individuals run, an entire city, an entire county, an entire world [will] come together to say that we will not be deterred."
In April, three people were killed and more than 200 were injured when two bombs went off at the finish line of the Boston Marathon.
The tragic event forced the Bank of America Chicago Marathon to step up security, increasing checkpoints, banning spectators from the start and finish lines, and requiring runners to pick up their own race-day packets.
"As we planned for this year's event, we were profoundly affected by what took place in Boston this past April," race director Carey Pinkowski said. "The heartbreaking events left a lasting impression on all of us, but it was evident to me and our organization how strong, how determined and united the running community it is. Together we move forward, we move forward with confidence."
Chicago Police Superintendent Garry McCarthy said this week there are no known threats to the city or the marathon.
Pinkowski and Emanuel said 45,000 runners and about 1.7 million spectators are expected in Chicago Sunday for the annual race, which draws an annual economic impact of $243 million for the city.
"The fact is that people keep coming back," Emanuel said. "We had a record number last year. We expect a record number of people running this year."