The hybrid approach would partially lower roadways and partially elevate rails, keeping the tracks lower than fully elevated. The crossings at Ravenswood, Oak Grove, Glenwood and Encinal avenues are all being altered, and thus far Ravenswood and Oak Grove have only been considered for fully elevated crossings.

Mayor Jen Wolosin said she worried that grade separation hasn't been a big enough priority, adding that the project came about following a death on the tracks in 2015. She said she was concerned that the timeline doesn't reflect that delays affect the safety of residents.

"I worry that it's going to take a tragedy to make us move fast," Wolosin said. "We've already had the tragedy, and now I'm (worried) it can take another tragedy."

Council member Betsy Nash said the idea of raising the tracks poses privacy concerns, and that Caltrain runs along a route directly adjacent to housing. The added elevation would put homes and backyards in full view, she said.

"I spent many, many years commuting on Caltrain, and one of the things you do on Caltrain is you sit on the upper deck and you look into people's backyards," Nash said. "This gives people much more visibility into backyards."

The council opted not to pursue fully elevated grade separation, with city staff saying that everything would have to go precisely as planned for the project to be completed on a five-year timeline. The lag time before construction could even begin is several years, due to construction and design demands.

"I'm really excited about the the most beautiful, most open option, creating space underneath the train," Council member Maria Doerr said.

The council unanimously gave Menlo Park city staff direction to pursue the hybrid method of grade separation, which will next be revisited at the annual budget meeting midyear.