Obviously, the quickest way to fill a service hole in the Northeast, connecting Washington/Baltimore with Harrisburg, would be to run the trains up the NEC to Perryville, and then up the Port Road to Harrisburg. However, the only intermediate stop in a town of any size would be at Columbia, PA. The service would be far more useful if it roughly followed the old route of the Northern Central between Baltimore and York, and thus would be able to allow passengers to avoid having to drive on I-83, which can be a very stressful drive, indeed.
Now, the original Northern Central between Baltimore and York has been totally abandoned and is now a very popular rail-trail. I would not suggest trying to revive the route because (1) I like hiking that trail, and (2) most of the development along the Baltimore-York corridor has moved to the area adjacent to I-83, so the original route isn't near where the passengers are. Thus, it's probably a better idea to build a whole new passenger right of way. It seems that the tracks are still in place north of York into Harrisburg, but the routing quickly leads to the Susquehanna River at York Haven and then follows the river up to the bridge crossing it into Harrisburg itself. Again, the alignment diverges from the I-83 corridor, where it seems that most of the current development is located.
The original line was built during a era (the 1840s) when trains could't take stiff grades and so were content to follow meandering river courses. It might have meant longer rides, but, hey, at 25 mph it was faster than a Conestoga wagon. Thus, from Baltimore it followed the Jones Falls, then at Cockeysville it crossed the divide and followed Gunpowder Falls and its tributaries until New Freedom, PA, where it crossed into the Codorus Creek watershed and followed that into York. Then it continued along that to the Susquehanna and followed the big river into Harrisburg.
Motor vehicles, on the other hand, can run on modern highways at full speed (70 mph) under some very stiff grades and even relatively sharp curves (try driving the Pennsylvania Turnpike between Blue Mountain and Irwin to see what I mean). A paralleling rail route would thus need to be able to have stiffer grades than what's currently common in the US rail network in order to have an alignment that would be competitive with I-83. I believe that's technically feasible, but would probably require a lot of spectacular cuts, fills, and viaducts to cross the hilly terrain of the Maryland Piedmont and adjoining hilly parts of Pennsylvania. It might actually be a pretty scenic ride, especially for it being essentially a commuter railroad.
Assuming that the political will could be found to actually build this thing (If we were China, it would probably be finished already as full 200 mph HSR, and if we were Europe, the old Northern Central would still be running, because it would never have been left to go totally to seed.) , I could see Amtrak trains running between Harrisburg and York, possibly extending into the Keystone and Pennsylvanian routes, and perhaps extending north along the Susquehanna to serve Scranton and Wilkes-Barre. Also MARC trains could run between York and Baltimore and Washington, and some sort of Pennsylvania commuter rail service could run between Harrisburg and York. Possible stops are:
Baltimore - Penn
Timonium (commuter)
Cockeysville/Hunt Valley
Hereford (commuter)
Maryland Line (commuter)
Shrewsbury (Pa)
Jacobus (commuter)
York
Manchester/Mt. Wolf (commuter)
Newberrytown/Yocumtown (commuter)
New Cumberland (commuter)
Lemoyne (commuter)
Harrisburg
One engineering problem is the alignment out of Baltimore. The Northern Central route is currently being used for a light rail line. I'm not sure that the double track route could handle the full mix of Amtrak, MARC, and light rail trains, but I'm not sure there's enough room along the route to expand the number of tracks. Perhaps they could double deck it that part of the line?
The current I-83 route is about 75 miles and takes about an hour and a half to drive if there are no traffic jams, so any rail service would have to be at least as fast as that.
I'll probably never see this happen in my lifetime, but one can always dream. And, boy, do I hate driving on I-83.
Now, the original Northern Central between Baltimore and York has been totally abandoned and is now a very popular rail-trail. I would not suggest trying to revive the route because (1) I like hiking that trail, and (2) most of the development along the Baltimore-York corridor has moved to the area adjacent to I-83, so the original route isn't near where the passengers are. Thus, it's probably a better idea to build a whole new passenger right of way. It seems that the tracks are still in place north of York into Harrisburg, but the routing quickly leads to the Susquehanna River at York Haven and then follows the river up to the bridge crossing it into Harrisburg itself. Again, the alignment diverges from the I-83 corridor, where it seems that most of the current development is located.
The original line was built during a era (the 1840s) when trains could't take stiff grades and so were content to follow meandering river courses. It might have meant longer rides, but, hey, at 25 mph it was faster than a Conestoga wagon. Thus, from Baltimore it followed the Jones Falls, then at Cockeysville it crossed the divide and followed Gunpowder Falls and its tributaries until New Freedom, PA, where it crossed into the Codorus Creek watershed and followed that into York. Then it continued along that to the Susquehanna and followed the big river into Harrisburg.
Motor vehicles, on the other hand, can run on modern highways at full speed (70 mph) under some very stiff grades and even relatively sharp curves (try driving the Pennsylvania Turnpike between Blue Mountain and Irwin to see what I mean). A paralleling rail route would thus need to be able to have stiffer grades than what's currently common in the US rail network in order to have an alignment that would be competitive with I-83. I believe that's technically feasible, but would probably require a lot of spectacular cuts, fills, and viaducts to cross the hilly terrain of the Maryland Piedmont and adjoining hilly parts of Pennsylvania. It might actually be a pretty scenic ride, especially for it being essentially a commuter railroad.
Assuming that the political will could be found to actually build this thing (If we were China, it would probably be finished already as full 200 mph HSR, and if we were Europe, the old Northern Central would still be running, because it would never have been left to go totally to seed.) , I could see Amtrak trains running between Harrisburg and York, possibly extending into the Keystone and Pennsylvanian routes, and perhaps extending north along the Susquehanna to serve Scranton and Wilkes-Barre. Also MARC trains could run between York and Baltimore and Washington, and some sort of Pennsylvania commuter rail service could run between Harrisburg and York. Possible stops are:
Baltimore - Penn
Timonium (commuter)
Cockeysville/Hunt Valley
Hereford (commuter)
Maryland Line (commuter)
Shrewsbury (Pa)
Jacobus (commuter)
York
Manchester/Mt. Wolf (commuter)
Newberrytown/Yocumtown (commuter)
New Cumberland (commuter)
Lemoyne (commuter)
Harrisburg
One engineering problem is the alignment out of Baltimore. The Northern Central route is currently being used for a light rail line. I'm not sure that the double track route could handle the full mix of Amtrak, MARC, and light rail trains, but I'm not sure there's enough room along the route to expand the number of tracks. Perhaps they could double deck it that part of the line?
The current I-83 route is about 75 miles and takes about an hour and a half to drive if there are no traffic jams, so any rail service would have to be at least as fast as that.
I'll probably never see this happen in my lifetime, but one can always dream. And, boy, do I hate driving on I-83.