For reference, the divided highway at upper left is Interstate 95. At top right is the Route 100 Industrial Park that is north of Dorsey, Maryland; at bottom left is CSX's Jessup Yard. Railcars are switched between the two with some regularity, traveling a one-way distance of a little over 3 miles.

The green line that runs almost between those two locations marks the Howard - Anne Arundel county border which, except for the upper right, is also the railroad line, and the route followed by this page. We begin near the "Jessup Station Park & Ride".

The view from Maryland 175 is obstructed but lets us see a pair of engines idling. Let's stop at Jessup Station for a better view.

As seen from Jessup Station, the signals are all red on the left (Track 2), but those on the right for Track 1 are showing some green, more specifically, Rule 1283, Medium Clear.

A westbound must be on the way.

Link: CSX signal aspects

Soon a short mixed freight rolls into view, tugged by CSX 836...

... with an assist from CSX 3307.

West of the station it switches to Track 2...

... and continues past an idling CSX 4300.

Since the duo is not immediately moving on, let us do so, with the goal of investigating the other train in view. Had you noticed the green trash cars in the CSX 836 photo above?

Here's an earlier view with deeper zoom. Waste Management's green cars are on Track 2 in the distance.

Upon moving the camera northeast a few miles, we find that the head end of the trash train is waiting at the Dorsey interlocking.

It has a red over red (Stop, Rule 1284), but the other track's yellow over red means Approach (Rule 1285). Beyond Dorsey Station, another signal is showing lunar (bluish white) used to express Restricting (Rule 1290). Restricting means the operator needs to proceed slowly enough to be able to stop the train upon sighting an obstruction.

I agree: the lamp color differences are not large. Indications had been much clearer with the B&O's CPL signals that conveyed instructions via two lamps. Alas, CSX chose to replace them with this style of signal. That's Maryland 100 crossing overhead at Dorsey Station.

As seen from Dorsey Station, this is the same Dorsey interlocking, but looking the opposite direction at a time when the color-position light signals (CPLs) were still on duty.

With CPLs, even if you could not discern the color, the angle of the imaginary line connecting the illuminated pair conveyed the basic instruction (go in the main photo, and stop in the photo at right). Details were supplied by the lamps above and below the central disk.

Most signal diplays tell the operator two things: the speed at which to operate here, and the speed ahead. Since many trains are heavy and require a long time to stop, the "speed ahead" information lets the operator know how to prepare for the next signal, one that might express a slower speed, or even to stop.

With large LED displays becoming common, if I were redesigning the system I would show the speed here and the speed ahead as simple numeric values, perhaps with various colors. For example, 20-0 would tell the operator speed 20 here, be prepared to stop (speed 0) at the next signal. Special situations could be represented by letters. For example, 10-X would mean speed 10 here, entering unsignalled territory next. Full stop would be shown as a red 0-0 which, coincidentally, would resemble the two red lamps of a B&O CPL signal. Other special instructions could be represented by blinking, underlines, a box around the digits, or similar.

Hey, look, those engines idling at Jessup have found their way here. The red diagonal approach sign means a temporary stop sign (red square) is ahead, such as one near track or signal maintenance. Perhaps you had noticed the red square stop sign in the Jessup Station photos above.

With CSX 6458 trailing, the duo is bound for the Route 100 Industrial Park. The lunar aspect in the distance reminds the operator the train will be entering unsignalled trackage. CSX 6458, model GP40-2, had been B&O 4444.

Link: B&O 4444

Lunar goes all red as the duo climbs the steep hill into the industrial park.

Next, track 2 gets a green, and the trash train resumes its trip. For the sake of train operators, if there are any stinky trash cars in the consist they're usually placed at the end.

At T:36 we reached the Route 100 bridge over the tracks, but that photo turned out poorly, so this is one from a prior year. The fortuitously-matching snow helps highlight the spur into the industrial park on the left. The next four photos also date from earlier, and are used for illustration purposes.

Dorsey Station's platform provides a better view of the spur into the Route 100 Industrial Park. CSX labels this location Thomas.

The track arrangement within the park limits options for engine placement. For example, the hoppers between the buildings at the bottom cannot be pulled back to the main (the SW/NE line at right) because there is no way to place the pair of engines in front of the hoppers without decoupling the engines. This is illustrated by the following two photos.

If you noticed these are not the same engines as before, I'm impressed. This and the next photo are from a different move, one during January 2019.

CSX 6419 and CSX 2235 can pull the hoppers out, but...

... the track configuration forces the engines to continue across San Tomas Road, pause while a track switch is flipped, and then reverse to push the covered hoppers out to the main line.

The two engines could be decoupled from each other, then some back and forth maneuvering done to shuffle both in front of the cars, but that's rarely done here since the process is time consuming, the consist short, and the trip to Jessup Yard but a few miles.

By the way, you won't find many trees closer to active tracks than some of these.

Now back to December 2020... this time the duo we've been following from Jessup is not pushing cars, but pulling them, which means this pickup happened elsewhere within the industrial park.

Here they lead the cars across Santa Barbara Court...

... and head back to the main line, with the engines leading down the hill.

To bookend this page, let's return to Jessup Station. On this day (snowless, sorry), hoppers like those we saw above were slowly pushed back to Jessup Yard. For such moves, a crew member is stationed on the end and remains in communication with the operator.