Highway Numerology Muddled by Potholes in Logic

The numbers assigned to California’s highways do more than merely mark asphalt pathways. They evoke definitive life experiences and regional subcultures, even the ghosts of history and myth.

The mere mention of Route 66 conjures images of Dust Bowl emigres and John Steinbeck’s “Mother Road.” Highway 1 promises a postcard California coast, world-class surfing and the mists of Big Sur. And 405 can only mean traffic without end--a multilane parking lot where many Southern Californians think they’ve wasted a good portion of their lives.

Even the straight, interminable I-5 holds inspiration for some, such as Rancho Cordova numerologist Janet K. Turner. “Five is freedom, individuality,” she says. “It gives us the freedom to travel.”

The real meanings behind such highway numeration are a little less romantic--though telling, nonetheless, of history, roadway hierarchies and many other things.

The federal government established a national numbered highway system in 1926 to bring order to the nation’s confusing collection of named regional roads, many of which were known only to locals. California followed suit with a set of numbers for state highways in 1934.

Today, the statewide commuter grid is made up of interstates, U.S. highways and state routes. The interstates, which comprise the nation’s premier highway system, are marked by blue-and-red shields, while the older U.S. highways are designated by black-and-white signs. State highways usually are marked with signs shaped like a garden spade.

Because each of these systems has its numbering quirks, a typical L.A. commute--say, a trip from Simi Valley to Studio City via the 118, 405 and 101--involves three different numbers that mean three different things.

The simplest rule that applies to all kinds of freeways in California--and all interstates around the country--is that odd-numbered roads usually run north-south and even-numbered roads run east-west.

California 118 will take you from Chatsworth in the San Fernando Valley to Mission Hills as sure as Interstate 10 (the Christopher Columbus Transcontinental Highway) spans the nation from Santa Monica to Jacksonville, Fla.

If freeways bend, they don’t get new numbers, they just foul up the beauty of the north-south/east-west rule. Consider the 101. To some local drivers, the freeway might seem to warrant an even-numbered designation, because it carries them east and west across the San Fernando Valley.

But the 101’s grander purpose is to get people up and down the Pacific Coast, thus its odd numerology.

The federal interstate system follows a few particular numbering rules that were developed by the U.S. government in 1957.

Much as the nation’s founders preferred easily manageable grids in plotting cities, Eisenhower-era bureaucrats set up a numbered, graph-paper highway network for the entire nation.

Under their plan, major interstates are assigned one- or two-digit numbers. The numbers for north-south routes get bigger as you travel east, while east-west routes get bigger as you travel north. Thus, I-95 and I-90 hang by the East Coast and meet in Boston, while I-8 and I-5 traverse the far west and intersect in San Diego. Moderate-sized numbers such as I-40 and I-44 appear, sure enough, in the heart of the country, Oklahoma City.

Three-digit numbers are reserved for interstate routes that branch off a major, long-distance route. The last two digits indicate the parent route. The “-05” in 405, for example, indicates the freeway feeds a principal route, I-5.

The first digit of a three-digit interstate explains the road’s function. If that first number is odd, it indicates a spur that runs directly to a city, the way the 710 terminates right in Long Beach.

When the first digit is even, it means the road makes a loop, or partial loop, around a metropolitan area. That’s the case with the 405 (San Diego) Freeway, which branches off I-5 near the city of San Fernando and traces a congested parabola through western L.A. and Orange counties, meeting its parent highway again in Irvine.

In the 1950s, the nascent interstate system began to replace the old U.S. highway system, which dates back to the 1920s. While roads such as Route 66 have been officially decommissioned, this original national highway network still has an important function: Many of its slower, narrower roads serve smaller communities and routes less traveled, and some, such as the 101, have been upgraded to superhighway status in some areas.

Major roads in this system have one- or two-digit numbers, while three-digit routes signify smaller spurs. But every road rule must have its exception and the 101 is a major one--a superhighway with a three-number designation.

The U.S. highways share some numbering traits with the interstates but reverse others. North-south routes also are odd, while east-west ones are even. But the numbers of the freeways grow larger as one travels from the East Coast to the West Coast--the opposite of the interstate system. That’s why California has U.S. Highway 101 and Maine has U.S. Highway 1.

There’s apparently no explanation as to why the federal government changed the numbering order from east-west to west-east between the generation of U.S. highways and interstates. “For some reason, they just flipped the high and low numbers,” said Lori Irving, a spokeswoman for the Federal Highway Administration.

If federal highway numerology is confusing, the state’s system is almost entirely random. Yes, odd-numbered highways tend to run north-south and even ones east-west, but there are no other firm guidelines.

“There’s not a real recipe,” said Caltrans spokesman Dennis Trujillo. Even the odd-even rule is flouted fairly routinely. The Antelope Valley (14) Freeway, for instance, heads essentially due north from the Los Angeles Basin through the high desert.

If the finer points of highway numerology are the province of transportation savants, the numbers still maintain a place in the popular conscience. And in commerce.

You can find the number 101, for example, gracing a drive-through restaurant in Willits, a fish and chips joint in Newark, a Laundromat in Crescent City and the 101 Driving School in Atascadero.

Marylou Whitley, the driving school’s owner, said she has no idea why the nearby U.S. highway got that number. But it’s proven easy for her customers to remember and great for business.

“I honestly believe the inspiration came from God,” she said, “because I’m not very good at this marketing stuff.”

Wait, God? What about the Federal Highway Administration?

“Yeah, OK,” she said. “Maybe a combination.”

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