The trip itself from Shady Grove to Dupont Circle made good time. I had just missed a train at SG and waited 9 minutes for the next train to come. It did leave after sitting for just 1 minute.
However, in the first 6 minutes of the commute, 4 trains passed going in the opposite direction. I don't understand why there was a 9-minute gap with subsequent trains so close together.
How long should the interval be between trains during peak/rush hour? Metro website says "Due to the high frequency of service, timetables for peak hours (weekdays 5-9:30 a.m. and 3-7 p.m.) are not available."
The Metro timetable for midday, available online
(http://www.wmata.com/pdfs/rail/Midday.pdf), show trains operating every 6 minutes during the mid-day.
This indicates that "high frequency" operations should have trains departing the station at less than 6-minute intervals during the peak/rush hour. In my experience, if things are running smoothly at SG, trains depart about every 6 minutes. I guess I'm a little confused by Metro.