PA State Highway 330

[Truvelo]

I took a photo of this plaque on a bridge on the edge of Pittsburgh. It mentions PA 330 but I can find no evidence that such a route number exists or has ever existed. There's also no evidence that PA 51 which passes through this junction had a different number in the past. I'm mystified as to why PA 330 is mentioned on the plaque.

[Roadsguy]

This can only be the effect of time travel, but for some reason this plaque was unaffected. Quick, contact your favorite secret paranormal investigation agency!

[Mapmikey]

330 was the state legislative number for PA 51.  See this map of Allegheny County.

At least some of those numbers match this 1924 statewide map

[Rothman]

The evidence is in the photo itself...

[Bitmapped]

330 was the state legislative number for PA 51.  See this map of Allegheny County.

This part of PA 51 was Legislative Route 330 up until the adoption of the current State Route system in the 1980s. Here is a 1976 Allegheny County map: https://gis.penndot.gov/BPR_PDF_FILES/MAPS/Type_10_GHS_Historical_Scans/Allegheny_1976_Sheet_1.pdf

Note that State Routes/State Highways are not synonymous with PA (Traffic) Routes. It's possible for a PA Route to have a different state route number than what is posted (like PA 86/SR 0886) or for a PA Route to not have a SR number at all because it is maintained by the local municipality (like PA 281 nearest the WV border in Henry Clay Township, Fayette County).

[Truvelo]

Thanks for the info regarding legislative numbers. Now I understand why PA 330 doesn't exist. It seems most, if not all, signed state routes have a different legislative number. I see PA 88 is known as 247. The real 247 is at the opposite end of the state. I assume this is avoid confusion if both 247's were in Pittsburgh.

[Bitmapped]

Thanks for the info regarding legislative numbers. Now I understand why PA 330 doesn't exist. It seems most, if not all, signed state routes have a different legislative number. I see PA 88 is known as 247. The real 247 is at the opposite end of the state. I assume this is avoid confusion if both 247's were in Pittsburgh.

Legislative routes were just for internal use. Other than that later on they went to assigning 5-digit numbers to additions to the system where the first two digits were a county code, I don't think there were any patterns. Things were just sequentially numbered as they were added. LR 247 and PA 247 being on opposite sides of the state was just coincidence.

PA traffic routes had an extremely well-defined clustering/family system at the beginning that is still readily apparent today. There is a good explanation at https://web.archive.org/web/20130511003629/http://www.m-plex.com/roads/numbering.html.

The Location Reference System of 1986 brought about the current State Route scheme and segment numbers to bring order to the legislative route chaos. Like Legislative Routes, they're still intended for internal use but you can see them marked with the little white signs at roughly 1/2-mile intervals and at major intersections. Here, every road gets a 4-digit number. If it is a PA traffic route, the SR number is generally just that padded out with zeroes at the beginning. Secondary routes are numbered based on the quadrant of the county they're in.