I mean, they've already got a dead-man's switch so that if the engineer becomes incapacitated, the train stops, not to mention a lot of logic that they can put on the trains. Are there many accidents that this would have prevented?

Interest in dead man's controls increased with the introduction of electric trams (streetcars in North America) and especially electrified rapid transit trains. The first widespread use came with the introduction of the mass-produced Birney One-Man Safety (tram) Car, though dead-man equipment was fairly rare on US streetcars until the successful PCC streetcar, which had a left-foot-operated dead man's pedal in conjunction with the right-foot-operated brake and power pedals. This layout has continued to be used on some modern trams around the world. In conventional steam railroad trains, there was always a second person with the engineer, the fireman, who could almost always bring the train to a stop if necessary.[2] For many decades two people were assigned to electric and diesel locomotives as well, even though a single person could theoretically operate them.

With modern urban and suburban railway systems, the driver is typically alone in an enclosed cab. Automatic devices were already beginning to be deployed on newer installations of the New York City Subway system in the early 20th century. The Malbone Street Wreck on the Brooklyn Rapid Transit system in 1918, though not caused by driver incapacitation, did spur the need for universal deployment of such devices to halt trains in the event of the operator's disability. According to a Manhattan borough historian, there have been at least three instances where the dead man's switch was used successfully – in 1927, 1940, and 2010.[3]

The status and operation of both vigilance and dead man's switch may be recorded on the train's event recorder (commonly known as a black box). Modern locomotive practice is to incorporate the dead-man's and vigilance functions under the control of the alerter or the event recorder.[4]

I mean, I get that locomotive engineers are gung-ho on the idea of more demand for locomotive engineers, but does this make sense from a safety standpoint?

googles

It sounds like this particular incident, a little over twenty years ago, might have been resolved with two people in the cab -- but it also ended without anyone being hurt, and required a complicated series of events to go wrong, where actions were taken that both disabled the dead man's switch and to set the train to accelerate. I'd think that one could reasonably change the UI on the controls to avoid that:

https://en.wikipedia.org/wiki/CSX_8888_incident

Before leaving the cab, the engineer applied the locomotive's independent air brake. During mainline operation, he would also have applied the automatic air brake, which would set the brakes in each of the train's cars. But, as is normal for intra-yard movements, the air brakes of the train were disconnected from the locomotive and thus were not functional. Furthermore, applying the locomotive's brakes disabled the train's dead man's switch, which would otherwise have applied the train brakes and cut the engine power.[1]

The engineer also attempted to apply the locomotive's dynamic brake to slow the train to a crawl; dynamic brakes dissipate momentum (kinetic energy) by using the momentum of the train to drive the traction motors, generating electricity exactly like a regenerative braking system does in a hybrid/electric automobile, which slows the train. However, the engineer "inadvertently failed to complete the selection process", meaning that he in effect set the train to accelerate, not to brake. Using the power throttle handle, the throttle for the traction motors was set at notch 8. If the dynamic brakes had been properly engaged as intended, the locomotive would have used the motors against the momentum of the train as generators, causing it to slow down. Instead, the train began to accelerate. Therefore, the only functioning brake was the air brakes on the locomotive, and this was not enough to counteract its power.[1]

The engineer climbed down from the cab, aligned the switch, and then attempted to reboard the accelerating locomotive. However, he was unable to do so and was dragged by #8888 for about 80 feet (24 m), receiving minor cuts and abrasions. The train rolled out of the yard and began a 65-mile (105 km) journey south through northwest Ohio unmanned. Attempts to derail the train using a portable derailer failed; the portable derailer was thrown off the track by the force of the train when struck. Police officers attempted to engage the red fuel cutoff button by shooting at it; after three shots mistakenly hit the larger red fuel cap, this ultimately had no effect because the button on former Conrail SD40-2s like CSX 8888 must be pressed for several seconds before the switch is activated, causing the engine to starve of diesel fuel and shut down.[7][8] A northbound freight train, Q636-15, was directed onto a siding where the crew uncoupled its locomotive, CSX #8392 (another EMD SD40-2), and waited for the runaway train to pass. #8392 had a crew of two: Jesse Knowlton, an engineer with 31 years of service; and Terry L. Forson, a conductor with one year's experience.[9] Together they chased the runaway train. An EMD GP40-2, CSX locomotive #6008, was prepared farther down the line to couple to the front of the runaway to slow it further, if necessary.[10]

Knowlton and Forson successfully coupled onto the rear car and slowed the train by applying the dynamic brakes on the chase locomotive. Once the runaway had slowed to 11 miles per hour (18 km/h), CSX trainmaster Jon Hosfeld ran alongside the train, climbed aboard, and shut down the engine. The train was stopped at the Ohio State Route 31 crossing, just southeast of Kenton, Ohio before reaching locomotive #6008. All the brake shoes on #8888 had been completely burned off by the heat, since they had been applied all throughout the runaway trip.[1]