{"schema":"https://ver.cy/schemas/card/1.0.0","id":"vr.tr.balloon-loop","code":"thing-q659909","url":"https://ver.cy/models/thing/q659909/","name":"balloon loop","alternateNames":["Toronto streetcar loop"],"kind":"thing","status":"published","version":"0.2.0-wave.3","language":"en","classifiers":{"family":"Thing Registry","category":"Physical world and living systems","entryKind":"thing","plane":"PHY","domain":["PHY.BLT"],"industry":[],"navPath":"","tags":[],"facets":{}},"whatItIs":"A loop of track at the end of a railway, tramway or streetcar line that lets a vehicle reverse direction without stopping or shunting by running around the loop, used at termini of streetcar systems such as Toronto, at metro and light rail terminals, on freight spurs and at tourist railways; balloon loops save time and allow single-ended vehicles, but need more land than a stub terminus or turntable.","purpose":"Let an agent explain balloon loops and their purpose, identify where they are used, relay design considerations and examples, and distinguish them from wyes, turntables and reversing sidings.","scope":{"in":[],"out":[],"boundaries":[]},"distinguishingFeatures":["Continuous turning","Suits single-ended vehicles","Land-hungry","Common on streetcar systems"],"structure":{"bundles":[{"id":"understand","name":"Understand","description":"What a balloon loop is.","layers":[{"id":"definition","name":"Definition","description":"Definition and purpose.","findings":[{"id":"definition-finding","name":"Definition","description":"Definition.","questions":[{"text":"What is a balloon loop, and why is it used?","kind":"definition"},{"text":"Is the arrangement a balloon loop, a wye, a turntable or a siding?","kind":"boundary"}]}]},{"id":"kinds","name":"Kinds","description":"Kinds and uses.","findings":[{"id":"kinds-finding","name":"Kinds","description":"Kinds.","questions":[{"text":"Where are balloon loops used, from streetcars to freight?","kind":"definition"},{"text":"Which entry fits the specific system?","kind":"action"}]}]}]},{"id":"design","name":"Design","description":"Design and operation.","layers":[{"id":"geometry","name":"Geometry","description":"Geometry.","findings":[{"id":"geometry-finding","name":"Geometry","description":"Geometry.","questions":[{"text":"What radii, gradients and clearances govern loop design?","kind":"provenance"},{"text":"Which references are standard?","kind":"provenance"}]}]},{"id":"operation","name":"Operation","description":"Operation.","findings":[{"id":"operation-finding","name":"Operation","description":"Operation.","questions":[{"text":"How are loops operated, including platforms and layover on the loop?","kind":"provenance"},{"text":"Which entry fits tram operation?","kind":"action"}]}]}]},{"id":"examples","name":"Examples","description":"Examples.","layers":[{"id":"toronto","name":"Toronto","description":"Toronto streetcar loops.","findings":[{"id":"toronto-finding","name":"Toronto","description":"Toronto.","questions":[{"text":"How does the Toronto streetcar system use loops, and which are notable?","kind":"provenance"},{"text":"Which entry fits Toronto streetcar system?","kind":"action"}]}]},{"id":"other","name":"Other","description":"Other examples.","findings":[{"id":"other-finding","name":"Other","description":"Other.","questions":[{"text":"Which other systems use balloon loops, including freight loops at mines and ports?","kind":"provenance"},{"text":"Which sources are cited?","kind":"provenance"}]}]}]},{"id":"context","name":"Context","description":"History and trade-offs.","layers":[{"id":"history","name":"History","description":"History.","findings":[{"id":"history-finding","name":"History","description":"History.","questions":[{"text":"How did balloon loops develop with single-ended streetcars?","kind":"provenance"},{"text":"Which entry fits the history of trams?","kind":"action"}]}]},{"id":"tradeoffs","name":"Trade-offs","description":"Trade-offs.","findings":[{"id":"tradeoffs-finding","name":"Tradeoffs","description":"Tradeoffs.","questions":[{"text":"When is a loop preferred over double-ended vehicles or other turning arrangements?","kind":"provenance"},{"text":"Which entry fits railway terminus?","kind":"action"}]}]}]}]},"agentConduct":{"may":["Describe balloon loops and where they are used, from railway and tram sources.","Report service changes from the operator's official data."],"mustNot":["Direct or move a train or tram through a loop without authority.","Let people onto the track inside a loop where vehicles turn.","Tamper with points or signals on the loop."],"requiresHuman":["Changing operations or access at a terminal loop."]},"ethics":{"considerations":["Turning vehicles can strike people who misjudge the track's curve.","Loops at termini are shared spaces for staff and passengers."],"affectedParties":["Passengers","Staff at terminals","Pedestrians nearby"]},"owners":{"steward":"The railway or tramway infrastructure manager.","roles":[],"masterSystems":[]},"relations":[{"target":"Q15079401","type":"parent","note":"registry parent class"},{"target":"Q21198029","type":"parent","note":"registry parent class"},{"target":"Q728937","type":"parent","note":"registry parent class"},{"target":"Q728943","type":"parent","note":"registry parent class"},{"target":"rail track","type":"related","note":"in registry terms"},{"target":"turning place","type":"related","note":"in registry terms"},{"target":"wye","type":"related","note":"another turning layout"},{"target":"tram","type":"related","note":"especially single-ended vehicles"}],"interaction":{"identity":{"applicability":"required","items":["Vercy registry: vr.tr.balloon-loop","Wikidata: Q659909 (https://www.wikidata.org/wiki/Q659909)"]},"properties":{"applicability":"required","items":["minimum radius: about 15-25 m - streetcars; larger for mainline vehicles"]},"recognition":{"applicability":"required","items":["Loop of track for turning without reversing","Streetcar, metro, freight and heritage uses","A wye reverses by three legs; a turntable rotates the vehicle; a reversing siding needs a change of ends","A circular or teardrop loop of track at a terminus, often with a platform on the loop."]},"capabilities":{"applicability":"required","items":["explain the layout and purpose","identify uses and examples","relay design considerations","distinguish from other turning arrangements"]},"hazards":{"applicability":"required","items":["Wheel and rail wear on tight curves","Noise and squeal","Land requirements"]},"interfaces":{"applicability":"required","items":["Track geometry standards for curves","Tramway and railway safety regulations"]},"context":{"applicability":"required","items":["Turning rail vehicles without reversing or shunting.","streetcar and tram loops such as the Toronto streetcar loops","metro and light rail terminal loops","freight balloon loops at mines and ports","heritage and tourist railway loops","loops within stations and depots"]}},"sources":[{"title":"Wikidata item Q659909: balloon loop","url":"https://www.wikidata.org/wiki/Q659909","note":"identity and sense of the item"},{"title":"Wikipedia: Balloon loop","url":"https://en.wikipedia.org/wiki/Balloon_loop","note":"general description of the item"}],"openQuestions":["Should streetcar loops be a separate entry?","How should track standards be linked?","The registry entry has merged an alias for Toronto loops; should it be split off?"],"resources":{"spec":"/models/things/publications/thing-q659909/spec.json"},"provenance":{"origin":"thing registry research (pass 2)","builtFrom":["models/things/publications/thing-q659909/spec.json"],"providers":["Claude"],"researchStatus":"unreviewed","generatedAt":"2026-09-12T23:27:52Z","builder":"tools/build_cards.py@1.0.0"},"completeness":{"sections":{"classifiers":"filled","whatItIs":"filled","purpose":"filled","distinguishingFeatures":"filled","structure":"filled","agentConduct":"filled","ethics":"filled","owners":"filled","relations":"filled","interaction.identity":"filled","interaction.properties":"filled","interaction.recognition":"filled","interaction.capabilities":"filled","interaction.hazards":"filled","interaction.interfaces":"filled","interaction.context":"filled","sources":"filled"},"notes":{"_gate":"Published through the thing publication gate 1.0 on 2026-10-06T19:52:01+00:00: completeness 1.00; sense: Wikidata description; 2 live sources; review by codex: pass"},"score":1.0}}