Backpacks or other bags larger than 8.5 inches by 11 inches by 4 inches will be banned from the 12K course, which spans from downtown San Francisco to Ocean Beach on the western end of the city.
Bomb technicians and canine units from the Police Department will be located along the course while police will also monitor cameras in real-time at the start and finish lines and at a hilly location along Hayes Street where crowds often gather for the race, police Chief Greg Suhr said.
A total of 17 law enforcement agencies, including the FBI, are contributing resources to ensure the safety of runners and spectators, Suhr said.
The city's Department of Public Works has also been replacing regular trashcans along the course with transparent ones so authorities can make sure nothing suspicious has been placed inside, Suhr said.
Organizers of Bay to Breakers, which is presented for the first time this year by the classified ads website Craigslist, are reimbursing all costs for law enforcement, Suhr said.
Race director Angela Fang said, "We're going to have the same great event that this city loves."
Matt Stiker, chief marketing officer of the San Francisco Travel Association, called Bay to Breakers a great example of the quirkiness of San Francisco.
The race is famous for the zany costumes worn by its participants, as well as the occasional runner wearing nothing at all. Stiker said the race is "a pressure release valve" for hard-working San Franciscans and "this city blows off steam like no one else does."
One costumed contestant will be Tom Sweeney, who has been a doorman at the city's Sir Francis Drake Hotel for 37 years and is running Bay to Breakers for the 40th time.
Sweeney has run the race for the past 15 years in his 40-pound beefeater outfit similar to the ones worn by guards at the Tower of London.
"It's not your everyday running outfit but I love the challenge," he said.
Sweeney is a native of San Francisco's Sunset District and grew up with Suhr, even briefly dating the police chief's sister.
He said he is always cheered on by his friends and other supporters when he runs the race.
"It's great, seeing all my friends," he said. "I look forward to this day every year."
Sweeney said he wasn't concerned about his safety in the wake of the Boston bombings, which killed three people and injured more than 200 others near the race's finish line in April.
"I think it will be the safest thing ever," he said. "Boston was unique but I think in San Francisco, everyone comes together. It should be a good year."
Olympian Ryan Hall, who holds the fastest marathon time ever run by an American, will be participating in the Bay to Breakers for the first time this year. Tesfaye Alemayehu, an Ethiopian who trains in Antioch and has three top-five finishes in the San Francisco race, is among other top competitors.
The race starts at 7 a.m. Sunday at Howard and Main streets and will affect San Francisco Municipal Railway bus lines along the course.
More than 25 Muni routes will be affected, including the F, N, 2, 5, 6, 8X, 9, 10, 12, 14, 14L, 18, 19, 21, 22, 24, 27, 28, 29, 30, 31, 33, 38, 43, 44, 45, 47, 49, 71 and 108 lines.
The Great Highway parking lot closed at 6 a.m. Thursday in advance of the event, while dozens of other streets will be closed shortly before and during the race.
A list of street closures and other information about the event can be found online at www.baytobreakers.com.