I-95 is north/southbound and existed east of I-99 long before 99 was built.
99 doesn't fit into the numbering scheme at all. The road shouldn't even be a two-digit number; it's not a major trunk route and it's entirely within a single state. It only serves to connect interstates 76 and 80, so it should have been a spur route of one of those.
Ah sheesh. I’ve been on that road many times (going from Lancaster county up to northern PA/southern NY) but didn’t realize it was entirely contained within PA. Your point about 95 is well taken. That’s messed up.
99 doesn't fit into the numbering scheme at all. The road shouldn't even be a two-digit number; it's not a major trunk route and it's entirely within a single state. It only serves to connect interstates 76 and 80, so it should have been a spur route of one of those.