Again, as far as I can tell, the Boston carbarn pavement was added when buses or trolleybuses began to use the carbarn in addition to streetcars.
In the single track part of the line east of Gary, South Shore has used spring switches at the ends of its long passing sidings. This can allow for running meets for passenger trains in some circumstances and has been described as a "poor man's CTC".
That would be a spring switch. Spring switches are fairly common at the end of double track and are sometimes found at the end of sidings that are normally entered from only one end. The throw rod is split into two sections with a spring - often enclosed in a steel tube - to push the points to the normal position. "Trailing" the switch - moving from the frog end to the point end - will push the points over without damaging the switch stand. Switch stands for spring switches are usually marked with a prominent "SS", and sometimes have a target of a different color than ordinary switches. The rules, for obvious reasons, require completing the trailing move across a spring switch vefore reversing direction.
One instead of two movable points and crowbar instead of motorized operation certainly simplifies installation and maintenance!
The Boston slip switches are built out of two point/frog/mate sets and ordinary switch frogs. The actual points are inserted into the p/f/m just like in ordinary single point switches, so there isn't a whole lot more to maintain. The overhead does require a special frog. A nice overhead view:
http://www.trolleymuseum.org/exhibits/guide.php
Just below the Burton B. Shaw South Boston Car House. That's TARS (New York) 631 in the loop.
During construction of Jerusalem Light Rail, the intersection was CLOSED and traffic detoured for one week. This was done in the summer of 2009, during a period when most Jerusalem firms gave employes vacations, to minimize traffic. I suspect when heavy maintenance is requried for the slip switch, they will have to repeat the process!
Whoever thought placing a puzzle switch in pavement was OK ought to be shot.
Sympathies to the track department folks who have to maintain the thing.
Nearly all Boston carbarns had at least one slip switch, sometimes a double, nd sometimes several. But the ones that were in pavement appear that originally they were open track with regular ties, and pavement was added when buses and trolleybuses entered operation from these locations.
But no slip switches on revenue track. A few placers looked like possibilities, but details showed to regular switches off the two revenue tracks, one slanted diamond, and a third switch merging the two lead tracks into one lead track.
For a nice aerial shot, look up Baumgartnerstrasse in Zurich on Google maps. There's a double slip behind Bhf. Wiedikon in the approach trackage to Depot Elizabethenstrasse.
I will explore the Bradley Boston Streetcar BSRA book. which has many detailed track plans of car houses, and get back to you. You may be correct. Zurich sounds interesting and possibly the hardwre is similar to Jerusalem's single example, even though meter gauge. (Jerusalem is standard.)
A mention of Baltimore on another forum reminded me of WB&A's terminal on Pratt St that had two single slip switches in the outbound joint (with B&O - think Docksides!) track from 1921 to 1935 to allow the loop to work in either direction. I don't know how they were operated, though I would guess in-street levers like WB&A used at their Washington terminal.
CTA has quite a few slip switches on rapid transit lines, including ones on the L structure. The "upstairs" yard at 61st st is full of them, and the ramp to the 63rd st lower yard is reached by two new ones installed across the main line in the 90s "Green Line" rehab. Almost all of the L lines have some at the end terminals.
Boston MTA had a number of slip switches in and around carhouses, at least some of them in pavement. A lot of them were of single point design, often switch iron only control. Seashore Trolley Museum has one in service, though not in pavement, that was at an MTA car house at one time.
In Switzerland the VBZ (Zuerich) has several meter gauge slips in pavement in service around car houses. I can't think of any in the streets except in the approach areas to the larger Tram Depots on non-revenue tracks. Most of the switches are dual point and power operated by in-street reed switches.
Of course rapid transit swithces are hardly ever in pavement. The slip switches in New York that I recall are at Myrtle Avenue and Broadway (Brooklyn) where the two-track Myrtle Avenue branch leaves the three-track Broadway elevated, and both Myrtle Avenue tracks have a connection to the center express track on Broadway, thus requiring two slip swithces, on on the center track and one on the westbound local track. A similar condition exists at Broadway Junction - Eat New York for the two tracks that ramp u to connect with the Canarsie line. On the Flushing No. 7 line, slip switches are used similarly at the ramp to the Corona yard and I believe a similar situation exists at the yard south of the 242nd Street Van Courtland Terminal of the 1 line. I cannot recall any on the old IND lines,. The elevateds had lots of them, inlcuding two at 149th and 3rd in the Bronx. None in pavement though.
Slip (or puzzle) switches are a complex piece of trackage, which goes a long way in explaining their rarity in street railway and rapid transit operations. CTA has some at the O'Hare terminal, and these are the only ones on the system.
Most classic trolley lines had one movable point and one split flangeway at each switch, and the point was moved with an iron bar held in place next to the controller by a clip on the front wall. When the switch point was motor operated, the motorman/operator would control the switch movement. Different systems had different protocoles for power on or power off through the contactors, some power on right, power off left, some power on diverging, power off straight etc. As a teenager, on many a fantrip I was the switch thrower for the operator and of course one of two helping with the trolley poles to change ends. Other kids reversed the seats.
But Jerualem light rail is a CTC operation with all switches controlled by the central dispatcher. All switches have two motorized points. And the position light signals are not only used for safety control, but are automaticlly timed (with Dispatcher override) to insure headway separation and no extreme bunching of trains due to delays. And there is a separate signal sysem using white horizontal and vertical bars in separate signal heads that is cooridinated with the vehicular traffic light signals at intersections. The operator has to have a clear signal from both signal systems before proceeding. Neither can be confused with the traffic signals for motorists.
I think Dublin and some European citiies are similar. But possibly lack a slip switch in pavement.
But wouldn't trolley lines have similar switches? Street running in industrial situations most likey would have been hand thrown. So, interesting question, Dave.
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Citypass Jerualem Light Rail has a powered single slip-switch in pavement used heavily by road traffic at the junction with the branch to the yard and shops. Is there any other example, on any type of railroad, that any reader of this post has seen? All points are powered and movable, but all frogs are fixed with flange running bridging the rail gaps.
Signals controlling the junction are position light mineaturs of PRR-N&W practice, but with different heads for each display.
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