Picture new Phoenix-size cities beyond the mountains to the far south and west of the Valley, and you get a glimpse of how the region's future might unfold over the next half-century.
Now imagine how twice as many people as live here today would get around such a vastly expanded urban landscape, and you begin to appreciate the enormous challenge facing state and regional transportation planners.
To cope with Arizona's anticipated long-range population boom, planners at the Maricopa Association of Governments have sketched out a far-reaching network of new freeways and highways beyond the White Tank and Estrella mountains, serving an area larger than Delaware and Rhode Island combined, and an urban landscape stretching as far as the Palo Verde Nuclear Generating Station.
MAG's plans envision 400 miles of new highways and 320 miles of rail track to support the millions of people projected to move into the vast desert area by 2050.
That would double the current highway system and create a commuter-rail network that would loop around the southern mountains and deliver a badly needed line to the West Valley. MAG estimates that it would cost the region a daunting $60 billion to build all the projects on its drawing boards.
Residents already concerned about sprawl wonder, with traffic and air quality as bad as they are today, how unbearable metropolitan Phoenix will become with 8 million people living here.
Others react with skepticism. They question whether the economy would ever be strong enough to lure such numbers of people here or whether sufficient water or electricity would be available to support such far-flung growth.
"Being able to stop all these people coming is probably impossible, but is this plan really possible? Could this really happen? And if it could, should it?" says Dave Richins, state policy director for the Sonoran Institute, a non-profit group that advocates desert preservation.
The strategy is based on decades-old migration and birth statistics and on existing land- development rights. Long-range plans for roads to serve non- existent cities don't foster speculative sprawl, the planners say; they anticipate what's already in the works.
The Arizona Department of Transportation is looking ahead and next month will unveil an expansive long-term blueprint for the entire state.
The agency's director, John Halikowski, described the scope as "breathtaking."
"This is a vision," Halikowski said. "I look at it with a great deal of excitement. Arizona is poised at the crossroads to decide what economic future it holds in store. I see it as a very bright future if we plan it right."
The alternative, planners insist, is worse.
Without such foresight, they see a region straining to keep up with unplanned growth. Rapid development outstrips the transportation network and overwhelms the highways. Rail lines are built through established neighborhoods. Sky-high costs pile up.
Regional and state agencies are striving to avoid that scenario.
This week, MAG's Regional Council is set to approve the concept, which is the second in a series of very long-range strategic plans.
The latest, called the Hidden Valley Framework Study, maps a new interstate looping far to the south and west around the Valley, with new freeways connecting it to the West Valley's Loop 303, Intestate 8 to the south and other new highways. The new interstate would divert truck traffic around Phoenix, serve the Valley's growth and ease traffic through downtown Phoenix.
A separate plan envisions a second bypass freeway taking I-10 traffic near Casa Grande to the East Valley near Superstition Vistas, out by Apache Junction.
And this fall MAG will complete yet another long-range blueprint. For mass transit, it calls for a commuter-rail loop in undeveloped desert. Paralleling the new interstate and connecting with existing freight track through Phoenix and Tempe, the new rail system would offer commuters options to driving and extend the reach of the Valley's backbone light-rail line.
ADOT is incorporating MAG's and other regions' work to map potential long-range transportation projects statewide for the first time. The two-year effort, involving hundreds of public meetings, seeks to accommodate 16 million Arizona residents by mid-century.
In October, ADOT will recommend the best Arizona-wide plan to a state panel and begin to estimate costs, capping an effort known as Building a Quality Arizona, or BQAZ. It's believed to be the farthest-reaching and most comprehensive plan of its kind.
Over the next two years, the state will identify priorities and how to pay for them.
The truth of any long-range plan falls somewhere between fantasy and inevitability.
Lines on maps take on a life of their own and shape future development decisions.
But times change, and with them commuter habits and desires. Predicting anything in transportation 50 years out is nearly impossible.
Arizona's recent short-range population forecasts proved notoriously optimistic. Now, in the midst of the worst economic slump since the Great Depression, in which Arizona's inflated housing market burst, few might believe predictions for millions more Arizonans.
It may take longer than projected, but history has proved it will happen eventually, planners say.
"I'm very comfortable with those projections," said Jim Zumpf, ADOT's project manager on BQAZ. "Knowing they are coming we have to plan for that or else face gridlock and air-quality concerns."
A lack of money is the one thing that most likely imperils BQAZ projects. At current levels, it would take 120 years of all of the state's transportation funding to build just Maricopa County's $60 billion of new infrastructure.
By comparison, the entire 56-mile Loop 202, which circles from I-10 in Phoenix through the East Valley back to I-10 in Chandler, cost $2.6 billion to plan, design and build, using a combination of gas tax and county sales-tax money.
Traditional sources, state and federal gas taxes, have lost buying power every year for two decades.
Every penny in gas tax generates $35 million in Arizona, Halikowski said. The 18-cent rate hasn't been increased since 1991.
"Obviously, the gas tax won't be the workhorse in coming years," he added. "It's really a 1950s model."
Toll roads already are being touted as one alternative for Arizona. Two I-10 bypasses to the West Valley and East Valley are considered likely candidates.
After passing a law this year allowing private investment in highways, Arizona could turn to private companies to build future highways and use tolls to pay the construction debt and upkeep. ADOT would choose the route, engineer the road and take over the highway when the debt is paid.
Even if the demographers are right, there is no guarantee that the region will develop in the way the planners anticipate.
There are three possible alternative scenarios.
• Growth slows or stops. The state runs low on water, electricity or economic lure to continue growing at a rapid pace. Congestion and air pollution don't get any worse, but a less-vibrant region creates fewer well-paid jobs and cultural attractions.
• Growth continues but more centrally. The region absorbs more of the new population closer to existing city centers than in the desert. This prompts a shift from highway to mass-transit investment.
• Growth continues uncontrollably. The region sprawls into the desert with no plan to move millions of people or the goods they need. Gridlock and smog worsen faster than highways and transit can be built.
Concern about this last alternative is what's spurring planners to imagine a distant future and explains why, ADOT says, the public has generally embraced the BQAZ concept in meetings and online. The consequences of inaction are obvious.
ADOT depicts those consequences with a series of color-coded maps showing how long it could take to get around the state. By 2050, traveling from Phoenix to most places in Arizona outside the Valley would be at least a five-hour trip.
"Ultimately, this plan is critical to the vibrancy of our state," said ADOT's deputy outreach director, Sally Sheffield. "It's not just about congestion. How did that milk get on your table? What did it cost to get there?"
MAG's project manager, Bob Hazlett, expects uncontrolled sprawl if the region's strategy is discarded. "If you don't like this, you get Riverside County," Hazlett said, referring to the sprawling desert county east of Los Angeles, one of the fastest-growing regions in the country and a symbol of traffic gridlock.
He and other experts cite local examples of the same problem: Anthem to the north and Buckeye to the west grew faster than the highways could handle. ADOT has scrambled to widen I-17 and I-10 earlier than planned, creating years of traffic-snarling construction. To the southeast, rapid development clogged rural roads like the Hunt Highway near Queen Creek. Closer to Phoenix, ADOT is still grappling with building the South Mountain Freeway through established neighborhoods, decades after the route appeared on plans.
Advocates of mass transit and compact growth accept the inevitable and credit ADOT and MAG for thinking ahead.
"You could put your head in the sand and hope people won't come," said David Schwarz, president of the Valley non-profit Friends of Transit. "I think you have to recognize that they will."
Jay Hicks, a local official with the Urban Land Institute, a national non-profit that promotes compact development, said: "We tend to get beaten up pretty badly about being a sprawling city, but we are really building our city for the first time.
"If we do it correctly and stay with the plan, we have a chance of making this a great place to live."
Said Halikowski: "If the plan languishes, Arizona becomes a pass-through for traffic heading to and from Los Angeles and to and from Mexico. Do you want to live in a crossroads or somewhere with all the things that made people want to live here in the first place?"
Local planners forecast huge increases in population and traffic in the next four decades. Here are some key statistics of what's expected and what's planned for coping with the changes.
2005: 5.8 mil
2050: 14-16 mil
2005: 3.8 mil
2050: 8 mil
Valley daily vehicle trips
2005: 10 mil
2050: 23 mil
Sources: Estimates from the Maricopa Association of Governments, U.S. Census Bureau
Emerging state and regional transportation plans include some bold ideas:
• Interstate 11: A 152-mile freeway from Casa Grande to Wickenburg running south and west of the Valley.
• Commuter-rail loop: A network for commuter trains from Coolidge to Goodyear and on to Phoenix, Tempe and back down the southeast Valley.
• A new type of major street called an Arizona parkway to move surface traffic more quickly. The four-lane street would carry as much traffic as an existing six-lane boulevard and flow as freely as a four-lane highway.
• A new reliever highway for I-17, from Wickenburg to Prescott and on to 1-17, giving people an option for traveling north and south if I-17 is congested.
• A tunnel under White Tank Mountain Regional Park. Still being studied, the tunnel would carry east-west parkway traffic near Northern Avenue from close to Luke Air Force Base to new suburbs west of the mountains.
The Arizona Department of Transportation, the Maricopa Association of Governments and other regional planners are developing numerous long-range transportation plans. Find their plans at the following Web sites:
• Clearinghouse for all state and regional plans:
• Arizona Department of Transportation's public awareness campaign:
• ADOT's travel time maps:
• An Urban Land Institute exercise:
View subscription options