"one engine in steam" meaning in English

{
  "head_templates": [
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      "args": {
        "1": "en",
        "2": "phrase"
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      "expansion": "one engine in steam",
      "name": "head"
    }
  ],
  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "senses": [
    {
      "categories": [
        {
          "kind": "other",
          "name": "British English",
          "parents": [],
          "source": "w"
        },
        {
          "kind": "other",
          "name": "English entries with incorrect language header",
          "parents": [
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          "kind": "topical",
          "langcode": "en",
          "name": "Rail transportation",
          "orig": "en:Rail transportation",
          "parents": [
            "Transport",
            "All topics",
            "Fundamental"
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      "examples": [
        {
          "ref": "1941 July, “The Isle of Man Railways”, in Railway Magazine, page 315",
          "text": "There are eight 4-wheel coaches of the open toastrack type, but provided with roofs, and during the holiday season, usually beginning at Whitsuntide, trains are run as required on the one-engine-in-steam principle.",
          "type": "quotation"
        },
        {
          "ref": "1960 March, “Talking of Trains: S.R. branch report”, in Trains Illustrated, page 135",
          "text": "A change seems likely on the Axminster-Lyme Regis branch [...]. We hear also that one-engine-in-steam operation will probably be introduced on this line.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "A principle in railway signalling where only one train or locomotive is allowed to run on a section of single-track line, such as a branch line, at any one time."
      ],
      "id": "en-one_engine_in_steam-en-phrase-4jXi-5sa",
      "links": [
        [
          "rail transport",
          "rail transport"
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        [
          "single-track",
          "single-track"
        ],
        [
          "branch line",
          "branch line"
        ]
      ],
      "raw_glosses": [
        "(rail transport, UK) A principle in railway signalling where only one train or locomotive is allowed to run on a section of single-track line, such as a branch line, at any one time."
      ],
      "related": [
        {
          "word": "in steam"
        }
      ],
      "tags": [
        "UK"
      ],
      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
    }
  ],
  "word": "one engine in steam"
}

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      "expansion": "one engine in steam",
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  "lang": "English",
  "lang_code": "en",
  "pos": "phrase",
  "related": [
    {
      "word": "in steam"
    }
  ],
  "senses": [
    {
      "categories": [
        "British English",
        "English entries with incorrect language header",
        "English lemmas",
        "English multiword terms",
        "English phrases",
        "English terms with quotations",
        "en:Rail transportation"
      ],
      "examples": [
        {
          "ref": "1941 July, “The Isle of Man Railways”, in Railway Magazine, page 315",
          "text": "There are eight 4-wheel coaches of the open toastrack type, but provided with roofs, and during the holiday season, usually beginning at Whitsuntide, trains are run as required on the one-engine-in-steam principle.",
          "type": "quotation"
        },
        {
          "ref": "1960 March, “Talking of Trains: S.R. branch report”, in Trains Illustrated, page 135",
          "text": "A change seems likely on the Axminster-Lyme Regis branch [...]. We hear also that one-engine-in-steam operation will probably be introduced on this line.",
          "type": "quotation"
        }
      ],
      "glosses": [
        "A principle in railway signalling where only one train or locomotive is allowed to run on a section of single-track line, such as a branch line, at any one time."
      ],
      "links": [
        [
          "rail transport",
          "rail transport"
        ],
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          "single-track",
          "single-track"
        ],
        [
          "branch line",
          "branch line"
        ]
      ],
      "raw_glosses": [
        "(rail transport, UK) A principle in railway signalling where only one train or locomotive is allowed to run on a section of single-track line, such as a branch line, at any one time."
      ],
      "tags": [
        "UK"
      ],
      "topics": [
        "rail-transport",
        "railways",
        "transport"
      ]
    }
  ],
  "word": "one engine in steam"
}