As I mentioned a couple of months ago, area code 918 is just about full, which means one of two options: either 918 is split into two different codes, one retaining 918 and the other being assigned a new number this was the action taken when 580 was spun off from 405 or an overlay is applied, which means that the 918 area remains intact but that new numbers will be assigned the new code.
Each of these has disadvantages. In a split, roughly half the customers suffer the inconvenience of a new number; in an overlay, all the customers suffer the inconvenience of having to dial ten digits instead of seven.
To my mind, an overlay makes sense in a metro area like DFW or New York where people are already using ten digits for many of their local phone calls calling from Dallas to Arlington or Brooklyn to Manhattan or where the area code that needs splitting is already a small area and there are no clean breaks between exchanges. Those conditions don’t obtain here in Oklahoma. It makes sense to do to the 918 what was done many years ago to 405 keep the existing code for the urbanized area and assign a new code to the outer area.
It should be noted that the reason DFW and New York are already using ten digits is that they’ve already had overlays, and Dallas and Fort Worth have been in different area codes more or less since Day One (which was in 1947) anyway. Come to think of it, 918 was originally a split from 405, implemented in late 1953.
And while I agree with Mr Bates that 918 should get the same treatment as 405 a split rather than an overlay splits are on the way out. There are three area-code changes in the works right now, two in southern California and one covering all of West Virginia, and all three are overlays. In fact, residents of north San Diego County in California actually fought for the overlay, since they were the ones scheduled to be split off into 442. Since this would have been the fifth area-code change in that area (213 to 714 to 619 to 760 to 442), I can’t say as I blame them.
As for the new code, we don’t know what it will be, but I expect it will start with 5.
Update, 5 January 2010: 539, in fact.