What Happened to Semaphore Signals? | History in the Dark

The most common reason these were replaced was that they had too many moving parts. The signal lights were invisible during sunny days. They needed maintenance lots of times.

Hearing the danger of the lower quadrant signals reminded me of Henry's Flying Kipper crash

Driver: "He mentioned go, slow, and stop. He should have also mentioned backing signals, eh Percy?" Percy (crossly): "Not funny driver."

Another issue with semaphores compared to colour lights is weather, especially snow and ice. See Abbots Ripton wreck of 21 Jan 1876. They (semaphores) do not need electricity of course, a major issue even to this day in remote locations.

On lower quadrant signals, the spectacle plate was a heavy casting that would put the signal back to danger if the cable snapped.

I worked for CSX and we still had some semaphore signals we used on the south end of the old Monon. Those trips started on L&N signals, we then ran of NS to get to the Monon track in New Albany, IN. We’d run on the ex-Monon to Mitchell, IN where we would get on the ex-B&O Cincinnati to St Louis mainline which has CPL signals. Four different signal systems in that one trip.

On the main line of the Aberdeen & Rockfish Railroad in NC, there is an old semaphore that's still standing on the outskirts of Fayetteville. Albeit it's no longer functioning, but it remains a popular spot for railfans.

I actually got the opportunity to see a semaphore signal at this trolley museum, oddly enough it was quite cool just to see the arm changing its position

I saw one at the Depot Museum in Cheyenne last year. You put a little coin in and it goes up or down.

All Traffic Halted

There are still semaphore signals in use at my local railway station Nunthorpe if anyone is curious. There is also a space for a second one on the east bound platform from a long closed line off to guisborough. I believe that they are still in use on the Tyne valley line.

Semaphore signals are still used in some places on the German rail system

4:12 ask Henry which one he rather have.

IIRC, the PRR used a positional light form with three lights that could be horizontal, at a 45 degree angle, and vertical.

In the UK we have a thing called Fixed Distant signals. They are, quite literally, distant signals fixed at a caution aspect. They are used on the approach to terminus stations, or at certain junctions, where you always want the driver to receive and have to acknowledge a warning sound. I bring them up because even on lines with colour light signalling, they are represented by a white board with a graphic of the black-and-yellow distant semaphore arm! (A colour light signal can be used of course, but is a potential failure point)

The former Southern Pacific Semaphore signals looked similar to the ones from Thomas and friends when I have Daylight 4449 shirts from Daylight sales when I see 4449 with those signals.

Nice work Darkness, very interesting.

Another big issue with semaphore signals that has lead to their decline is that they each are operated by a cable connected to a lever in a signal box. This has a few issues. For a start, there are limits to how far the distance can be between the signal and the lever, since longer distances not only make it harder to pull the lever, but also mean more expansion and contraction with temperature changes. At least in the UK, it's quite common to see distant signals replaced with colour lights even where other semaphores remain. This means you need more signal boxes, basically one for every section of track, since signals can't be operated remotely. Colour lights mean that many signal boxes can be replaced and signals operated from a location many miles away. Also, in areas such as big stations or major junctions, there can be many signals, sometimes many arms on a single post with stop and distant arms, arms for diverging routes, shunt arms etc. Each of these needs a cable and a lever, so you get complicated cable runs with pulleys to keep the cables apart, and long lever frames. These often require a number of people to operate, and it's hard, physical work. On the other hand with colour lights, a single person can operate the same station or junction by pushing a few buttons or these days a few clicks of a mouse. Finally, everything is manual, there is no automation. With colour lights for example, they are usually set so that they automatically go back to red when a train passes, and on open track without junctions they are usually set to go back to green once the train is far enough away that another train can follow. Modern systems can even control junctions automatically, using the trains ID to know where it needs to go. Semaphores though need to be manually set danger to clear and back to danger, making them much more labour insensitive, and also restricting capacity (since there is more work needed to be done after one train has passed before it's safe for another train to approach). It wasn't uncommon for a signal box at the approach to a major station to have 6 or so people working in it at a time. With colour lights, those same 6 people could control the station and 100miles of track approaching it. These days, more like 1000miles (not necessarily in a straight line, but all the branches too). Also on the complexity, as well as the signals themselves, there is also the issue of the interlocking to make sure that everything is done safely. Originally this was all mechanical, using slides and cams, but later electrical locking was also used. Colour light interlocking can be done with relays, or these days with solid state systems. More reliable due to less (or no) moving parts, and taking up much less space. Old signal boxes were usually two storey, with the lever frames in the top, and the bottom being the interlocking. There is also the problem of the fact that the expertise to maintain and repair these sort of complex mechanical systems is disappearing.

I do believe that semefore signals are still use at Worcester Shrub Hill on the Snow Hill Line between Birmingham and Worcester here in the UK Darkness. I'm about 50/50 on that.

There is still 2 operating lower quadrant signals 160km from Sydney New South Wales on the south Coast line