Palo Alto's effort to reconfigure its four rail crossings will reach a critical juncture next month, when the City Council is set to eliminate dozens of options from consideration.

In addition to narrowing the list of 34 design options presented by transportation staff to about 10, the council will also decide whether to officially abandon seemingly the most popular and decidedly the most costly alternative: an underground tunnel for trains stretching along the entire 4-mile rail corridor in Palo Alto.

For city staff, redesigning the rail intersections has become increasingly urgent. Palo Alto is one of three cities -- along with Mountain View and Sunnyvale -- vying for $700 million in grade-separation funding from Santa Clara County through Measure B, the 2016 sales tax increase.

Last Wednesday, as the council's Rail Committee debated the virtues and impacts of design options, Palo Alto City Manager James Keene noted that the other cities are far ahead of Palo Alto and likened the city's position to a "caboose" on a train in a Western movie.

"There is always a scene where they go climbing and they unhitch the caboose and let it go and keep on riding the train," Keene said, after Councilwoman Lydia Kou suggested that the city continue to study a tunnel option. "Mountain View has half the crossings we have and has already made a decision on what they want to do, and we can't narrow it down to 10 crossings.

"The rest of the world is unhitching the train for us, and they'll happily sit back and watch us study."

To catch up, it's critical for Palo Alto to start making decisions, he said. The council's Rail Committee largely agreed as it voted unanimously to support a list of 10 design options for the city's four grade crossings -- Palo Alto Avenue, Churchill Avenue, Meadow Drive and Charleston Road.

At the city's northern-most crossing, Palo Alto Avenue, planning staff is proposing three different concepts: closing Palo Alto Avenue to car traffic (and possibly pedestrians and bicycles) and adding amenities elsewhere (such as a new bike undercrossing at Everett Avenue or a widened University Avenue undercrossing); a "no build" alternative that leaves it largely as is, with limited upgrades to improve safety; and a "hybrid" option in which the road is submerged in a shallow trench and the railroad tracks are slightly raised.

On Churchill, the city is also considering three alternatives: the "no build" option with safety upgrades; the closure of Churchill with more significant improvements such as a new bike tunnel or a widened Embarcadero Road; and the hybrid option.

The Meadow crossing also comes with a "no build" alternative.

The final three options pertain to both Meadow and Charleston (the only crossing where "no build" is not considered viable): a train trench in south Palo Alto that would go past these two crossings; and two different hybrid options, one with the tracks over the roads and the other with roads over the tracks.

One option that staff has recommended eliminating from consideration is a citywide trench or tunnel: a popular option that a recent analysis showed could cost between $2.4 billion and $4 billion.

While some residents have argued that the city should continue to study this alternative and to consider creative ways to finance it, possibly through sale of development rights, staff had determined that its cost -- magnitudes higher than other options -- constitutes a "fatal flaw."

Keene also rejected the notion that the city could receive the needed federal and state funding to make such an option viable, particularly if Palo Alto is acting alone.

"There would have to be aspects way more regional and our regional partners would have to be saying what we're saying now, and they're not," Keene said. "They are proceeding on different tracks, and they're ahead of us."

Kou wasn't entirely convinced. The city should continue to study the tunnel option, she said, and staff should provide more evidence for why this is impossible. In eliminating the tunnel idea, the council would not be doing a service to the region's "long-term outlook," which will inevitably include a larger population in more densely packed cities.

"I'm not willing to settle nor be pushed on this big endeavor," Kou said.

Though Kou was initially hesitant to support the winnowed down list, she ultimately voted along with her three committee colleagues after they agreed to include to keep the tunnel option alive -- if for no other reason than due diligence.

"I think a tunnel is completely infeasible, but I think there is a number of council members who will want to discuss it, so it's premature to exclude it from the discussion," Councilman Greg Scharff said shortly before the vote.

Councilman Adrian Fine also said he wasn't optimistic about the tunnel option. The city, he noted, doesn't even own the land on which the rail corridor is located. And financing the tunnel through sale of development rights would require the city to accommodate between 3 million and 4 million square feet of new commercial development.

"That's two Salesforce Towers," Fine said. "I don't think that's a realistic option for Palo Alto."

In addition to the 10 options recommended by staff and the underground tunnel, the committee also recommended that staff add to the list a possible overhead viaduct for trains over the two south Palo Alto crossings, an addition that was recommended by committee Chair Cory Wolbach.

The committee also proved sympathetic to requests from neighbors near the Churchill crossing, about 300 of whom had submitted a petition arguing against design options that would necessitate property seizures through eminent domain. Residents, group member David Shen said, don't want their neighborhood "destroyed with a concrete structure in the middle of it that increase traffic, decreases safety."

The group, Shen said, is more open to "closing Churchill and looking at the system of roads that include Embarcadero and Churchill together to improve traffic circulation in the area, not just for cars but also for pedestrians and cyclists."

The Rail Committee's recommendation carries extra weight in the grade-separation debate because three members of the full council -- Mayor Liz Kniss, Vice Mayor Eric Filseth and Councilman Tom DuBois -- are recused from the issue because of property interests near the tracks.

This leaves Greg Tanaka and Karen Holman as the only two council members who are eligible to participate in the discussion, which is tentatively set for May 14.

The goal for the city is to select by June between four and eight options for further analysis -- an exercise that staff estimates will cost between $200,000 and $300,000 per alternative, a cost that would come out of the city's General Fund. The city would then select its preferred solution by December.