I-95 in Maryland: milepost starting point?

[Michael in Philly]

My trivia question of the day (but one that's often bugged me) is:  what is the starting point for numbering mileposts on 95 in Maryland:  the Maryland/DC line?  the DC/Virginia line?  the mid-point of the bridge?  heck, the Maryland end of the bridge?  Obviously, if the DC segment were more than 200 feet long and had actual connections to the DC road system, it'd be a no-brainer, but as it is I always think of 95 as crossing the Maryland/Virginia line.  Does anyone know?  The mileposts don't actually appear on the bridge, at least the last time I was there.

[J N Winkler]

Logically, it would have to be the Maryland/DC line, but since 200 feet not only is less than one-twentieth of a mile but also is a plausible length for a station adjustment, I don't think anyone could tell just by using an odometer precise down to tenths of a mile.  I don't recall that any of the MdSHA plans for the Wilson Bridge gave station locations for milemarkers.

[oscar]

Another possibility, though also trivially different from the others, is that I-95's mileposting was based on where the old Wilson Bridge crossed into MD from DC, and not updated since the bridge was replaced.  That point would be a few hundred feet NE of the DC/MD line at the centerline of the new Wilson Bridge.

[froggie]

Oscar, the overall MD mileposting didn't change, but SHA instslled 0.2mi markers between the bridge and St Barnabas, which are roughly 0.5-0.7mi off from the original mileposts.  So to answer Michael's original question, it'd be wherever the original control point on the old Wilson Bridge was.

[Michael in Philly]

Oscar, the overall MD mileposting didn't change, but SHA instslled 0.2mi markers between the bridge and St Barnabas, which are roughly 0.5-0.7mi off from the original mileposts.  So to answer Michael's original question, it'd be wherever the original control point on the old Wilson Bridge was.

That's really not much of an answer to Michael's original question.... 

[froggie]

This should be, then:  according to their Highway Reference Logs, SHA defines "Mile 0" as the west (Virginia) end of the bridge, not the state line(s).

[NE2]

You're right - http://www.roads.maryland.gov/Location/2009_PRINCEGEORGES.pdf (p. 8)
Confusingly it also says the state line is at mile 0, but 1.161 matches the full bridge length from Royal Street in Alexandria.

BUT BUT BUT note where the mile markers are:
1 1.26
2 2.28
4 3.90
5 4.84
7 7.03
8 7.823
9 8.85
10 9.68
1 and 2 appear to be based off a zero about halfway between Lee Street and the shore.

This explains any discrepancy between the (original?) mileposts and new 1/5 markers. Do the new ones match the official mileage (1.2 just east of the ped overpass, for example)?

[Michael in Philly]

^^Thanks to both of you.

Somewhere in northeastern Maryland, I think I've seen a new-style milepost (the kind with the little Interstate shield in it) and an older one for the same mile - on opposite sides of the southbound roadway if memory serves - and they're some distance apart.  Wasn't sure if it was a mistake (meaning, one of them's at the wrong space) or they remeasured and neglected to remove the old one.