How are distances for highway signs measured?

Where the concrete lines meet is the point for San Francisco! Its GPS location is 37°46'48.2"N 122°24'49.2"W ( = 37.780059, -122.413657).

Our guide for the murals in the Mission District today was quite a character, but he reported that highway driving distances to San Francisco use this point because this is where the steps for city hall used to be.

I wanted to "fact-check" this and I found a short article about highway driving distance signs by Jim Lacy (July 14, 2006), http://www.sco.wisc.edu/news/are-we-there-yet-how-are-distances-for-highway-signs-measured.html » “According to Ken Cowan at the Wisconsin Department of Transportation (DOT), distances shown on highway signs (e.g. Madison 45, Waunakee 9, etc.), are measured to a major intersection or prominent building at the geographic center of the municipality. DOT’s procedure follows the Manual of Uniform Traffic Control Devices, as published by the Federal Highway Administration.

“Similarly, for the mileage log on the official state highway map, DOT uses GIS software to determine the center point. Then they pick the nearest major intersection, and use that point for computing distances between cities.

“A common misconception is that distances shown on highway signs are always measured to the location of the main post office in the municipality. This probably stems from the historic methods the U.S. Geological Survey (USGS) used for identifying populated places on the their maps. According to the USGS Geographic Names Information System (GNIS) metadata: ‘The primary point of a populated place is the center of original place, if known, such as the city or town hall, main post office, or town square regardless of changes over time.’ Although it was once safe to assume the post office was in the center of town, times have changed, and that is no longer the case.

All that said, I’ll probably tell my kids ‘we’re here’ when we hit the city limits on our next road trip!”

1 year ago (“Zebra swallowtail (on Sweet basil)”): http://365project.org/rhoing/365/2015-07-21
2 years ago (“Crab spider”): http://365project.org/rhoing/365/2014-07-21
3 years ago (“Christine”): http://365project.org/rhoing/365/2013-07-21
4 years ago (“Nashoba Valley Winery”): http://365project.org/rhoing/365/2012-07-21
5 years ago (“Before”): http://365project.org/rhoing/365/2011-07-21

[ IMG_1631S96x44Atm :: f/10 :: 1/400" :: ISO-800 :: 17mm ]

[GaryW]

Great shot and very interesting information...it seems, as with so many things, there is no consistency!!