Popisil is riding to raise money for breast, prostate and pancreatic cancer research.
This afternoon, San Francisco police officers are escorting him and his two team members from the north end of the Golden Gate Bridge to a reception at the Kabuki Hotel in Japantown.
Once they are across the bridge, a larger contingent of public safety officials will be waiting on the south side to join the group on their way to the hotel, Sgt. Andray Chak said.
They are scheduled to arrive at the reception at 3 p.m.
San Francisco marks the riders' third major destination on their journey, dubbed "Three Countries-Three Cancers Police/Firefighters Cycle for Cancer." The last stopover was in Astoria, Oregon.
Today's ride and gathering are a good opportunity for local officials to show their solidarity with Popisil, according to Chak.
"Police and fire service are like a family," Chak said. "We wanted to be there to support our friends."
In addition, Chak said, such a pervasive and tragic illness is reason enough to band together.
"Cancer is something that has probably touched everyone's lives in some degree, so that's another reason why it's important for us to get together and stand up to this illness," Chak said.