I just moved to DC to start college at American University, where (starting this semester) all students get unlimited Metro Rail and Bus for $130 per semester (that sounds like a lot, but some commuters can use that up in a couple of weeks; I've certainly used more than that in the last 2.5 months). Therefore, I've had my fair share of exploring the state of the DC Metro system as it is now.
Unfortunately, SafeTrack is needed to solve the 40 years of deferred maintenance the system has, which was covered up by the now-fired "safety" managers. Metro is being very cautious about safety now with the FTA watching their every move. This includes continuing to run the trains under manual operation.
Honestly, the jerking happens system-wide. I believe mfastx is correct that this is caused by the other components of the ATC system operating while the trains are under manual operation. About a month ago, I was sitting in the first car of a train and was able to watch a train operator through the tinted glass because I was traveling on elevated track on the Green Line in daylight. I noticed how the train slowed down without him doing anything, and then he would have to pull the throttle back and then forward again to get the train moving faster again.
One of the major aspects of the work happening under SafeTrack is for ATC, such as the replacement and/or repair of Intrusion Detection Warning boxes, which, from the name, seems to be what is preventing them from reintroducing full ATC operation.
If you're a nerd like me and interested in projects happening around you, feel free to take a look at http://www.wmata.com.../safetrack.cfm? where you can look at reports of what work Metro has done with each SafeTrack Surge. Here's the latest one going on now: http://www.wmata.com...ss Report_1.pdf
One good thing is that the new 7000-series cars are a much smoother and quieter ride than the older ones, which helps with the jerky movements.
Time will tell if this work will mean the use of ATC again. And let's all pray they seriously don't reduce the operating hours even more. It's already ridiculous closing the system at midnight seven days a week. Can anyone tell me why they can't do maintenance while keeping the system operational like other subway systems around the country? How other cities do both at the same time is over my head, but I feel like the capital of the United States should be able to figure it out...oh wait...Congress is in DC, and they don't do much about transportation anyway...