How much of of the system has motor ridden (cumalatively?)

I boarded my first Metro train in the summer of 1979 at Judiciary Square (where ground was first broken in 1969). My most recent ride was in 2005.

Here's a rundown of the total portion of the system I've ridden.

Trunk lines:

Blue/Orange from D&G Jct. to Rosslyn

Yellow/Green from F&L Jct. to Gallery Place

Blue/Yellow from Pentagon to C&J Jct.

Now the stand alone lines:

Orange: New Carrollton to D&G Jct. and Rosslyn to Vienna
(between those stretches and the Or/Blue trunk line, I've ridden every mile of the Orange Line, the only WMATA Metro line I've ridden in its entirety.)

Blue: Rosslyn to Pentagon and C&J Jct. to Van Dorn

Yellow: C&J Jct. to Huntington

Red: Wheaton to Bethesda

Green: I've never ridden the stand alone stretches of the Green Line.

ADDENDUM:

Here are the stations I've boarded or alighted at in my Metro riding career, in no particular order...

New Carrollton
Landover
Stadium-Armory
Capitol South
Federal Center
L'Enfant Plz (transferred between levels here)
Smithsonian
Fed. Triangle
Metro Center (transferred between levels here)
McPherson Sq.
Farragut West
Foggy Bottom
Rosslyn
Court House
Ballston
Vienna
Arlington Cemetery
Pentagon
Crystal City
Reagan National Airport
King St.
Huntington
Van Dorn
Wheaton
Forest Glen
Silver Spring
Union Station
Judiciary Sq.
Gallery Place (transferred between levels here)
Tenleytown
Bethesda

motor

Try going all the waym to Shady Grove and Glenmont on the Red Line next time. Shady Grove is at surface and in a nice area.