It's hard to predict the future, and downright impossible to analyze the impacts of developments yet unbuilt, technologies yet untested and policies yet undreamed of.

That, however, is the unenviable task facing Palo Alto's planners, elected officials and citizen volunteers. In order to set policies that will result in a future people will actually want to live in, city leaders since 2006 have been updating the city's Comprehensive Plan, the foundational document that purportedly guides all of the city's zoning laws, policies and new development.

Earlier this month, to aid in the protracted and expensive update effort, the city unveiled the Draft Environmental Impact Report (DEIR), which analyzes various strategies for city growth. The 837-page state-mandated study specifically considers four different scenarios that the city could pursue between now and 2030 and predicts how the city's appearance, traffic congestion and noise levels would alter under each path.

Filled with maps, tables and charts, the document is the most significant report produced to date over the decade-long history of the Comprehensive Plan update. The idea is that the city will look at each scenario and then either pick the one that looks most acceptable -- or mix-and-match them to arrive at the sweet spot for growth.

The document is at once ambitious and sobering, rich with data but short on solutions for the two problems that continue to fluster officials and residents alike: excessive traffic and insufficient housing. A recent survey commissioned by City Auditor Harriet Richardson showed the percentage of people rating traffic flow on local streets as "good" or "excellent" dropping from 47 to 31 percent between 2010 and 2015, while the proportion of respondents giving good grades to "ease of travel by public transportation" plummeted from 62 percent to 26 percent during the same period.

On housing, survey results continue to be abysmal, with only 20 percent giving the city good grades for "variety of housing" last year (down from 27 percent in 2014). And while 68 percent rated Palo Alto as a "good" or "excellent" place to retire in 2006, only 52 percent gave the city those same marks last year.

To underscore the severity of the problems, residents (a group that includes high-tech professionals and local attorneys; Stanford University students and recent Palo Alto High School graduates; millennials who live with their parents and empty-nesters looking to downsize) have flocked to council meetings in recent months to call for the construction of more housing.

For them, the big new document offers little hope. Under all four growth scenarios, the vast majority of the city, including single-family neighborhoods and open space preserves, would remain mostly untouched by new developments and policies, aside from the construction of a few dozen "granny units."

And even with traffic improvements such as expanded expressways, improved bike boulevards and a below-street-level railroad system, traffic jams will remain the norm during peak commute hours, according to the Draft Environmental Impact Report.

So what are these four paths to the future? One scenario considers what Palo Alto would look like if it continues on its present path, with no substantive policy changes (called the "business as usual" scenario). There's also a plan for reducing commercial growth; another for encouraging more housing; and a fourth for allowing more "sustainable" development.

Each presents a different level of growth, though as the DEIR points out, "All of the scenarios generally aim to facilitate the pace of residential and commercial growth by directing growth to specific areas through zoning incentives."

Despite the city's enormous housing challenges and a gaping jobs-housing imbalance (there are about three jobs in Palo Alto for every employed resident), land-use designations throughout the city would remain unchanged, with the sole exception of the Fry's Electronics area. There would be no new employment districts and, even in the most extreme scenario, no zoning changes to residential neighborhoods.

Yet the four scenarios also have some key differences between them. The first shows the city operating under the existing Comprehensive Plan, with "no innovations in housing," no new approaches to address the high cost of housing and no new growth-management measures. The employment base would grow by about 1 percent by 2030 in this scenario, which translates to 15,480 new jobs by 2030.

The second scenario, known as "Growth Slowed" would try to slow down the rate of job growth by moderating the pace of new office and research-and-development construction. While it wouldn't identify any new housing sites, it would include policies to encourage new housing units for seniors and the Palo Alto workforce, according to the DEIR. It would also concentrate the new housing in downtown, along El Camino Real, at the Fry's site close to the California Avenue Business District, and along San Antonio Road.

Housing is also the main focus on the third scenario, which isn't as concerned about slowing growth as the first two. Known as "Housing Reconsidered" in the DEIR, this scenario would focus housing in downtown and around California Avenue, in "pedestrian and transit-oriented districts" (PTOD) and remove potential housing sites from south Palo Alto, where transit services aren't as readily available. This scenario, much like the second, would also include a new "concept plan" for California Avenue, which would aim to maintain the district's character and discourage chain stores and restaurants from moving in.

The fourth scenario is the most aggressive and experimental. Limits on new building would be removed from downtown and replaced by "net zero" performance standards -- that is, requiring developments to create no additional problems, such as more traffic. Policies and regulations would be enacted to advance what the DEIR calls "sustainability objectives."

This means encouraging the provision of public-transit passes for residents in transit-served areas, the environmental LEED-platinum certification for new developments, local solar-energy production, foregoing new natural-gas hookups and installing drought-tolerant landscaping, according to the DEIR. Like the third scenario, it would also consider relaxing height limits for downtown buildings, to encourage new housing developments.

Unlike the third one, it would also try to add a PTOD designation, which allows greater density, to the Fry's Electronics site, the Stanford Research Park and Stanford Shopping Center, in hopes of encouraging mixed housing/retail/office developments there. And while most developments along El Camino Real would be two or three stories, some would be allowed to exceed the 50-foot height limit if they serve as "models of sustainability."

The four scenarios aren't set in stone. On Feb. 22, the council will consider a staff proposal for a fifth scenario, which the council requested last month. Though it hasn't yet been drafted, the fifth scenario is expected to add another $150,000 to the update process and require the city to perform a supplemental environmental analysis. If things, for once, go as planned with the convoluted process, the Comprehensive Plan will at last be adopted in May 2017.

Digging into the root cause

• See a chart on the Palo Alto jobs/housing imbalance under the various scenarios

People usually discuss Palo Alto's housing and traffic crises in one of two ways. Some, focusing on the symptoms, pointing to congested highways and priced-out teachers, techies and seniors. Others focus on the root cause: the fact that there are about three jobs in Palo Alto for every employed resident.

Barring major policy changes, the trend isn't expected to abate any time soon. Using job projections from the Association of Bay Area Governments, the draft environmental study estimates that the number of jobs in Palo Alto will rise from 95,460 in 2014 to 110,940 in 2030, while the number of employed Palo Alto residents will go from 31,165 in 2014 to 34,697 in 2030.

By the city's projection, the ratio of jobs-to-employed residents in Palo Alto -- generally known as the "jobs-housing balance" or, in Palo Alto, as the "jobs-housing imbalance" -- is expected to go from an already high level of 3.06 to 3.20 under the "business as usual" scenario (this is compared to the current Bay Area ratio of 1.03 and the Santa Clara County ratio of 1.14).

A new report from the city's Department of Planning and Community Environment notes that the city's imbalance between jobs and employed residents "contributes to local and regional traffic, greenhouse gas emissions and other impacts, as some workers travel long distances between their residence and workplace."

"The imbalance is projected to grow if the City does not take affirmative steps to address the issue," the staff report states.

Yet none of the four scenarios in the DEIR really address this problem. In each case, the ratio of jobs to employed residents ends up just above 3.0 in 2030. Even the "sustainability tested" scenario, which in theory could allow the city to build housing at much higher densities, would result in a ratio of 3.04.

Councilman Tom DuBois recognized this intractable problem on Jan. 19, when he requested a fifth scenario that would consider ways to reduce the ratio -- a suggestion that his colleagues endorsed. DuBois specifically requested a scenario with slower growth projections and "a decrease of people commuting to Palo Alto."

"What would a 2.5 jobs-housing scenario would look like?" DuBois asked.

The new report from the planning department suggests that such a scenario would be difficult, if not impossible, to achieve. The three typical ways to address the topic, the report notes, are increasing housing production, decreasing job growth or a combination of the two.

"Any decision made to increase the rate of housing production or decrease the rate of job growth can be highly contentious because of fears they will affect a community's character, its place in the larger region, and/or other economic and social concerns," the report states.

Three of the scenarios (all except "business as usual") proposed include modest steps toward keeping the ratio from getting worse. Ideas for increasing housing include encouraging smaller units, increased housing density near California Avenue and downtown, the relaxation of the 50-foot height limit in downtown, and new housing sites along the El Camino Real frontage of Stanford Research Park and Stanford Shopping Center.

To slow job growth, the scenarios consider policies that reduce how densely buildings can be constructed in some commercial districts and maintain an annual limit on office and research-and-development projects. By combining pro-housing and anti-jobs policies from the various scenarios, the ratio could the ratio dip to 2.88 by 2030.

By and large, the DEIR takes a cautious approach toward reducing the jobs-housing imbalance. The new report from planning staff notes that the city could potentially pursue other, admittedly more controversial, concepts to lower the ratio further. These could include creating new zoning districts that allow more than 40 housing units per acre (the limit in the city's R-40 zones); expand existing multi-family residential zones; and significantly downzone commercial areas. The DEIR generally avoids what the new staff report calls a "difficult conversation."

Yet some members of the Citizens Advisory Committee for the Comprehensive Plan have been urging the council to consider more aggressive policies on housing. Elaine Uang, a member of the committee and co-founder of the grassroots group Palo Alto Forward, was one of several members of the community who urged the council at the Jan. 29 meeting to consider the impacts of restrictive housing policies on seniors, teachers, emergency responders and others who are getting priced out of the city.

"I think we already have a lot of unintended consequences of housing policies for the past 30 years," Uang said. "It's the lack of diversity. It's people being pushed out of the community even though they have lived here for a long time because they can't afford it and they don't have options."

At least one council member agrees that the city should evaluate more aggressive housing policies, if only for comparison purposes. Cory Wolbach said there should be a scenario with more housing than the city is likely to choose. Some cities, Wolbach noted, are considering 30 percent increases in housing.

"Do we want to meet our share of the county's population growth or do more than our share because we've spent 40 years restricting population growth here?" Wolbach asked.

All those cars

• See map of predicted traffic hot spots

If the jobs and housing projections in the Draft Environmental Impact Report are somewhat worrying, the traffic projections in the document are downright grim.

In projecting future traffic levels, the report considers a variety of significant infrastructure improvements, including (in Scenario 2) a proposal by Santa Clara County to eventually build over- or underpasses to separate Foothill Expressway at its intersections with Page Mill and Arastradero roads and (in Scenarios 3 and 4) a rail system that would run in a trench below ground level. It then looks at existing and projected traffic levels and evaluates the impact of these projects on traffic flow at 14 major intersections.

In a few cases, the investments are projected to make a significant difference. Reconstructing Foothill Expressway so that it runs either over or under Arastradero would, for example, change the "level of service" at this intersections from "F" (the lowest possible level) to "A" during the peak evening commute hour and from "D" to "A" during the morning peak.

By and large, however, traffic is expected to get worse under all four scenarios, with or without these investments. In the "business as usual" scenario, six of the 14 intersections would see significant and unavoidable impacts (for Scenarios 2, 3 and 4, the number of impacted intersections are three, four and five, respectively).

The intersection of Foothill and Page Mill, which already operates at "F," would see conditions deteriorate further under three of the four scenarios. The average delay for a car trying to during this intersection during peak evening commute hour is expected to grow from 189.7 seconds to more than 300 seconds in three of the four scenarios. Only Scenario 2, which includes grade separation at this intersection, would lift the level of service to the still-dismal "D," according to the DEIR.

Some intersections are projected to experience significant and unavoidable impacts in all four scenarios. This includes the intersection of El Camino Real and San Antonio Road, where the existing level of service "D" is projected to become "F" during the evening peak hour no matter which path the city chooses. The intersection of Alma Street and Charleston Road is also expected to deteriorate from "D" to "F," with average delay for motorists during the evening commute growing from 48.6 seconds to 88.9 seconds in Scenario 1 and to 81.4 seconds in Scenario 2. Only in Scenarios 3 and 4, which include grade separation at the railroad crossing, does this intersection retain its "D" level of service.

Local highway segments don't look much better. Following Yogi Berra's paradoxical philosophy of "Nobody goes there anymore; it's too crowded," the DEIR predicts that there would actually be a decrease in the number of Palo Alto-related trips under all four scenarios because the highway segments will be so congested. The traffic model used in the DEIR projects a 25 to 30 percent increase in regional freeway volumes in 2030.

"Because the freeways would become so much more congested by 2030, the model's trip-assignment process assumes that many people will seek alternate routes in order to avoid the freeways," the DEIR states.

Some drivers would presumably switch to other modes, like Caltrain. Others would probably simply take different routes, whether Foothill Expressway, El Camino Real or Alma Street.

Yet the analysis also indicates that some highway segments will see significant slowdowns, with impacts deemed significant and unavoidable. On U.S. Highway 101, the list of impacted segments includes the stretch between Rengstorff Avenue and San Antonio Road (both northbound and southbound); between San Antonio and Oregon Expressway (also in both directions); and between Embarcadero Road and University Avenue (northbound). On Interstate 280, the two impacted segments will be the northbound and southbound stretches between Woodside Road and Sand Hill Road.

At a time when traffic congestion is the public's top complaint and the council's top priority, the numbers in the DEIR offer no cause for celebration. Yet as several members of the Citizen Advisory Committee pointed out during the committee's recent discussion of the Transportation Element, "level of service" measures don't tell the full story.

Whitney McNair, director of land use planning at Stanford University and a non-voting member of the citizens group, noted at the committee's Jan. 26 meeting that the level of service metric is somewhat outdated. Increasingly, planners are shifting to the "motor vehicles miles traveled" (VMT) model, which does not concern itself with wait times at intersections. Rather, it measures success by the reduction of vehicle trips and miles traveled.

Uang, a member of the Citizen Advisory Committee's transportation subcommittee, said the metric shouldn't be "just about the flow of cars." Ultimately, it should be about the "flow of people."

For instance, if a place goes from a system in which 800 people get around by cars, 100 by bikes and 100 by walking to one in which 500 use cars, 300 use bikes and 200 walk, that's "kind of a win," Uang said, even if the traffic conditions for the drivers worsen somewhat.

"The level of service will probably go down for the car, it might go up for bikes and up for pedestrians, but overall I think it's a system positive," she said.

But perhaps the best hope for Palo Alto of 2030 may lie with the free market, which fueled the city's economic prosperity and, in doing so, exacerbated its growing pains. Already, companies and agencies around Palo Alto are making adjustments to the worsening conditions on local roads. Stanford University is moving along with a plan to add 2,000 beds for graduate students at Escondido Village, reducing those residents' commute distance. And high-tech companies are revising work schedules, adding commuter shuttles and instituting telecommuting policies to make life easier for their commuting employees.

Some of downtown's leading companies are participating in the city's nascent Transportation Management Association, a nonprofit devoted to encouraging employees to shift from driving solo in cars to using other modes of transportation.

A similar effort is now under way at Stanford Research Park, which includes about 150 major employers. McNair noted at the Jan. 26 meeting that the biggest employers at Stanford Research Park have recently formed a transportation-demand-management working group in order to craft strategies and implement "what are anticipated to be the most effective transportation-demand-management programs on a Research Park-wide basis." The group plans to conduct a survey in the spring to get a better sense of the how the park's employees get to and from work, McNair said.

"Employers are inherently motivated to offer alternative means to get to their businesses because it's taking its toll on everybody -- employees and employers alike," McNair said.

Then there are the broader cultural shifts at play in the Valley: millennials who eschew cars in favor of Uber and Lyft; jobs that once required a science lab but now can be performed at home on a laptop; and the distant but potentially revolutionary prospect of self-driving cars.

Uncertainty over new technology is already causing divisions among members of the Citizens Advisory Committee, with some calling for abolition of minimum parking requirements for new developments on the grounds that people now drive less and others arguing that these requirements remain necessary because parking congestion remains the sad reality.

Bonnie Packer, a member of the citizens group, said on Jan. 26 that her vision for Palo Alto includes enhanced transit services that eventually make parking garages unnecessary.

"If we ever get this transit thing going and the parking demand -- at least in downtown -- has been reduced significantly, then we can tear (the parking garages) down and build affordable housing, which doesn't need so much parking," Packer said.

Emerging commuter trends and technologies could potentially dislodge the DEIR's bleak projections and present Palo Alto officials with new policy options for reducing traffic -- whether it's relying on Lyft to ferry local employees to a Caltrain station or unleashing a fleet of city shuttles with flexible routes around town based on demand.

Some of these policies will be further explored in the city's new Sustainability and Climate Action Plan, which is being undertaken in conjunction with the Comprehensive Plan update and is also set for adoption in 2017.

In discussing the sustainability plan at a January meeting, Mayor Pat Burt observed that one challenge that the city faces when it comes to long-term planning is the difficulty of predicting dramatic technological shifts.

"Looking in the rear view mirror is not necessarily the best way to predict the future," Burt said.

The same can be said for the council's ongoing effort to update its Comprehensive Plan and to lay a new foundation for local policies until the plan's expiration in 2030.

The Palo Alto City Council will be considering adding a fifth scenario for the Draft Environmental Impact Report on Feb. 22. The meeting will be held at City Hall, 250 Hamilton Ave., starting at 7 p.m.

To view the DEIR, go to paloaltocompplan.org