Why Not Use 8‑digit Local Numbers?

With the dizzying pace of area code splits, resulting in area codes the size of a smallish postage stamp, one of the suggestions that often comes up is "Instead of all these insane splits, why don't we just let the big cities have longer local numbers?" Many other countries even have variable length numbering schemes, where most small towns have 5- or 6‑digit numbers, and big cities have 7- or 8‑digit numbers, or even a mix of number lengths within a city or town.

The NANP is set up on a 3‑3‑4 numbering scheme

The entire North American Numbering Plan is constructed around the fixed‑length numbering scheme that each area code is three digits, followed by a three‑digit prefix and a four‑digit line number. Those assumptions are built into the NANP at many different levels, from administrative policy to the actual wiring of telephone switching equipment.

The association of each prefix with a specific company's switch in a particular central office is gradually eroding with the introduction of Local Number Portability (LNP). In its most basic form, LNP allows a customer to change Local Exchange Carriers (LECs) while retaining the same number, so long as the location is the same, or at least within the same rate center (town or portion of a city). In the future, however, LNP may be expanded to allow the customer to retain the same number even when moving to a different rate center — possibly even to a different state.

However, even the limited version of LNP that is currently being implemented is enormously complicated. Within areas that have LNP, every single call requires a database lookup to determine the correct LEC and switch in order to route the call. If LNP expands to a national or even statewide scope, the added complexity in call routing will be staggering.

Europe (etc.) has variable‑length numbers. Why can't we?

The fixed‑length numbering scheme used in North America allows the originating switch to reliably determine that the full destination number has been dialed, and transmit the entire number to the network in a single signalling block. In countries that have variable‑length numbers, any call outside the local area requires sending each digit individually to the network, with an acknowledgement sent back from the destination switch when a complete valid number has been received. It is substantially more efficient to transmit a single 10‑digit number than to transmit ten (or eleven or nine) individual digits.

How about assigning a block of area codes to a big city?

One proposal often floated for dealing with the explosion of area codes in a metropolis is to assign a block of consecutive area codes. Callers outside the area would dial the normal 10‑digit number, 1‑NPA‑NXXߛXXXX. However, callers inside the metropolitan area could dial the last digit of the area code and then the 7‑digit number, making effectively an 8‑digit local number.

For instance, let's say that we assign Los Angeles County the area code 59. We could then map the existing area codes as follows:

There are several flaws in this plan. First of all, these blocks of area codes would have to be assigned in groups of ten, although only 8 of the area codes could be used. If an area needed fewer than 8 area codes, the extras would also be wasted, because it would be confusing to assign them elsewhere. In the example here, we wouldn't want to assign 597 or 599 in another area, but we also wouldn't want to assign 590 or 591 at all, since that would be confusing. (There is also the issue that all codes with the second and third digits the same — for example, 599 — are reserved as "easy to recognize" codes for non‑geographic purposes.)

Still and all, what happens about five years from now when Los Angeles County needs its ninth area code? (Not counting the fact that a large portion of northern Los Angeles County is already in area code 805, and smaller portions are in 909, 714, and 760) Well, we just have to split area code 59, and we're right back where we started.

There's also the issue of how we make the transition. Outside the area, it's a simple and straightforward matter of permissive dialing. For a period of several months, you can dial either 213 or 592, for instance, and then an intercept recording will direct you to the new code. Inside the metropolitan region, though, there would be strong pressure to allow permissive dialing of either the old 7‑digit number or the new 8‑digit number. Unfortunately, the only way to distinguish between 2NXXߛXXX<pause>X and 2NXߛXXXX is by letting the switch time out if you dial only 7 digits — the switch waits a certain interval to see if you dial the eighth digit. If you make the interval too short, then you dramatically increase the number of misdials; if you make it too long, customers become annoyed at the long call setup time.

There is also the issue of where we get these blocks of numbers. The example above is entirely fictitious — area codes with 9 as the second digit cannot be assigned, because they are reserved for future expansion. There are, as of this writing, only nine blocks of ten area codes that have no announced assignments. Two of these (37X and 96X) are reserved for special purposes, and it is unlikely that they would be released for something like our example here. The other seven may have codes already reserved, and in any case are likely to have codes assigned before long.

The bottom line is that the plan of assigning a block of area codes to a large metro area is unworkable because it is inflexible and impossible to implement without massive disruption, and it leaves no method of providing further relief if needed in the future.

Massive costs of changing the phone number format

Any change in telephone numbering that breaks the assumption of 3‑3‑4 numbers will impose massive costs, both on the telephone companies and on customers of all sizes. Every telephone switch in North America is built on the assumption that numbers are 3‑3‑4, and changing that basic assumption will be difficult, time‑consuming, and enormously expensive. It will require literally decades of planning. At this stage, a target date of 2015 would be a tight schedule, and the total expense will run well into the billions of dollars.

In addition, every company PBX assumes that numbers are 3‑3‑4, so those will also have to be replaced, or at least given major (and expensive) upgrades. Consider the costs and confusion that were created simply by breaking the assumption that the middle digit of an area code is always 0 or 1! Innumerable database programs are hard‑wired to the notion of 3‑3‑4. Many numeric pagers assume that numbers are 3‑3‑4 for display purposes, and the display is often twelve characters, to accommodate ten‑digit numbers with two dashes. All of these pieces of customer equipment will be made less handy, or even made obsolete. Again, we're talking about many billions of dollars, just to upgrade the necessary equipment to continue functioning. Asking businesses to make that sort of investment again requires many, many years of advance notice.

The bottom line: billions of dollars and years of planning to make any change on this scale.

The short-term solution

The short‑term solution is to view telephone numbers, at least in large metropolitan areas like Los Angeles, New York, and Chicago, as TEN‑DIGIT numbers. Think of the area code as more of a "super‑prefix" instead of an area code. Then assign area codes as overlays. How many people can tell you the area code for an arbitrary address in Los Angeles County? Dozens of communities straddle at least one area code boundary. There is already no longer any meaningful geographic association between the area code and the tiny chunk of land it serves — area code 213 is already only 9 square miles, but it will split again in 1998. With an overlay, every existing customer gets to keep the same number. No new business cards, signs, brochures, or other costly changes for businesses; no annoying changes for residential customers. There has been strong customer resistance to overlays because of the irrational fear of having to dial the entire 10‑digit number on every call, but in a place like Los Angeles, anything past your own block is liable to be in a different area code anyway, and no one seems to be unable to cope with the need to dial the full number on calls from Covina to Compton, or Glendora to Glendale, or even western West Hollywood to eastern West Hollywood. I grew up in an area that had only a single prefix. Every number was 239‑xxxx. Then a second prefix was added, and suddenly some people had 233 numbers, and then later 661 and 387. As each new prefix came into service, it was a bit unfamiliar, but it quickly became part of the neighborhood. You might even see a business with a main number in the 233 prefix, but a 387 fax number; no big deal. The same will happen with overlay area codes. Marylanders are gradually getting accustomed to seeing the first few 240 and 443 numbers, but as they see more and more of them in the months to come, the new area codes will lose their unfamiliarity and even their novelty value and fall into the category of "just another number."

There are still situations in which geographic splits make the most sense. For example, area code 512 in south Texas is expected to require relief within the next one to two years. It currently serves two major cities, Austin and Corpus Christi. It makes sense to split 512, giving each city a separate identity numerically. Even some lopsided splits could make sense, such as cutting Marin County into its own area code before instituting an overlay in the remaining (San Francisco) area of 415. However, making any further geographic splits in dense areas like Los Angeles, New York, Chicago, Dallas, Houston, Atlanta, Fort Lauderdale, and Miami, is the essence of absurdity.

The long-term solution

All area codes with '9' as the second digit are reserved for future expansion of the North American Numbering Plan. I have outlined a specific elaboration of the idea, proposing to move to both four‑digit area codes and four‑digit prefixes. My plan would provide enough numbering resources to allow every parakeet in Los Angeles to have separate numbers for his cellphone, fax, and cellular fax. It would also have the side benefit of allowing for a period of ten to twenty years without additional splits or overlays, even in the fastest‑growing metropolitan areas. For more details about my proposal, please visit the

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