I don't know much about the Northeast Corridor these days; I worked there before Amtrak came into being. It is a four track railroad. I imagine there are drills on it serving local customers.
When I worked there the Pennsylvania had plenty of freight on it, heading towards and from the New Jersey side of the Hudson River. It didn't interfere with the passenger trains. Both passenger and freight were fast, though not as fast as today.
Our first high speed trains were the Metrolinres, originally EMUs, in 1969. just before we got the Metroliners, the railroad modified the interlocking machines in the towers along the way, so that if you pulled up a signal, you had to run the slow releas, to get the lever back, even if nothing was on the approach.
When I worked there the Pennsylvania had plenty of freight on it, heading towards and from the New Jersey side of the Hudson River. It didn't interfere with the passenger trains. Both passenger and freight were fast, though not as fast as today.
Our first high speed trains were the Metrolinres, originally EMUs, in 1969. just before we got the Metroliners, the railroad modified the interlocking machines in the towers along the way, so that if you pulled up a signal, you had to run the slow releas, to get the lever back, even if nothing was on the approach.