看得見的那張紙：畫著道路的地圖
這一家就是字面本身，也是其他用法借去的畫面來源。
noun · B1
A map that shows the roads of an area so that a driver can find the way from one place to another; it may also show things like hills, rivers or railway lines.
公路地圖
核心畫面
A big folded sheet opened on a table, covered in roads. Thick lines for the main , thin ones for the small ones, towns marked along the way. You put a finger on where you are, another on where you want to be, and the sheet answers one question: what do I pass through to get from here to there? Every other use keeps that answer and drops the paper.
可以想成一張攤在桌上的大紙，上面全是路。主要幹道畫得粗，小路畫得細，沿路標著城鎮。你一隻手指按住現在的位置，另一隻按…更多收起
可以想成一張攤在桌上的大紙，上面全是路。主要幹道畫得粗，小路畫得細，沿路標著城鎮。你一隻手指按住現在的位置，另一隻按住想去的地方，這張紙就回答一個問題：從這裡到那裡，中間要經過哪些點？後面那些用法都留著這個答案，只是把紙拿掉了——變成一份計畫、一份指南，照樣告訴你先到哪、再到哪。From the word’s history
The source records this compound simply as 'From road + map' — a map of roads. The later uses keep the shape of that object (a route with points along it) while the roads themselves drop away.
來源記的字源很單純：road（道路）加 map（地圖），就是一張畫著道路的地圖。後來的用法留下了這個東西的形狀——一條有沿途節點的路線——而真正的馬路不見了。
Wiktionary (kaikki extract) entry for 'road map', etymology_text: 'From road + map.'
Two branches
把路線借去講計畫：分階段走到遠方的目標
紙拿掉，路線留著：目標在遠處，中間切成幾個要經過的點，先到哪、再到哪講得清清楚楚。這是畫面上的借用，不是說計畫這個意思比較晚才出現的歷史主張。
noun · B2
A plan, often drawn as a chart or timeline, showing what a company or team means to build or change and in what order, over months or years.
發展藍圖；路線圖