The ICC mandated the introduction of ATC in 1922. PRR's first installation was in 1923 and they made the decision at that time to integrate cab signals with ATC. Harrisburg to Baltimore was equipped for ATC and cab signalling by 1927, and it was extended to Washington not long afterwards.

PRR Washington to New York had cab signals in the 1930s. The line has some form of train control now, but probably not in 1929.

Looks like PRR began installing train control (that is, automatic brake application if the engineer ignores a restrictive signal) in 1951. (Railway Age, 12 March 1951 p93 -- it's online at hathitrust.org.)

The locked box on the pilot beam is an instrument case for the Union Switch & Signal automatic train control equipment.

Guessing the lock box on the pilot beam contains tools and parts for quick maintenance on the road, stuff like extra lenses for the marker lamps, air and steam heat hose connections, etc, as well as the green and white flags mounted high on the locomotive which would indicate the train is running as a second section or an extra movement. At first I thought it might hold red (emergency stop) flags, fusees, and explosive "torpedoes", which are clipped to a rail and go bang when something runs over them, signaling the engineer for an emergency stop. These items, being needed by the crew quickly in an emergency, would be kept in the cab, as they still are today.

K-4 Pacifics would run on the Pennsy until 1957, but by 1935 the rails between DC and New York were electrified with overhead wires, and steam became a rarity on the line now known as the Northeast Corridor.

Here are an engineer and fireman whose garments will never again appear so pristine. In the glorious days of steam, anything forward of the baggage car was filthy work indeed, and even the most assiduous washing resulted merely in progressively more faded coveralls, with coal, smoke, and cinder stains intact.

The "s" suffix in the PRR steam locomotive classification scheme denotes the presence of a superheater. PRR supposedly stopped using the "s" suffix in 1923, as by this time, the superheater was a standard design element. Nonetheless, you commonly see these locomotives referred to as K-4s. The 5401 was indeed built in 1927. Here she is a few years later looking a bit grimier:

built in 1927, 92 were built, Baldwin built all locomotives from 5400 to 5474, all other K-4s were built by PRR in the Juanita Juniata shops.

What is the locked box on the front of the engine for?

A really great photo, notice the PRR emblem on the steam valve cover above the piston.

...must be the one in the white frilly dress.

OK, what the thingie hanging from the train: an anchor line?

[My guess: part of the bottle-breaking ritual mentioned in Washington Post story. - tterrace]

[It's the bottle holder. - Dave]

On Amtrak's Acela Express the trip can be made in 6 hours and 40 minutes.

---

Washington Post, July 14, 1929.

New Boston Train to Be Christened

Ten-year-old Ellen Page Eaton will break a bottle of Potomac River water on the locomotive of a new Pennsylvania Railroad train this morning at 11 o'clock in the Union Station and christen it “The Senator.” The train will give the fastest service between Washington and Boston.

After christening, the train will be open to inspection until its time of departure, 12:30 p.m. The train is scheduled to arrive in Boston at 10 p.m., cutting 3½ hours off the time previously made by the other two Pennsylvania line trains to Boston, The Federal and the Colonial expresses.

“The Senator” will be an all-Pullman train with dining, observation and club cars. It will make stops at New York City, New Haven and Providence.

Little Miss Eaton, who will christen the train, is the daughter of John Eaton, crack engineer of the railroad, who is veteran of 28 years. …

What a great pic! Is this one of those 1927 K-4's? Help us out PRR friends! Thanks for posting!