Question: When 4744 is the avg. trips per mile (x1000) what is the current stock?
SQL: SELECT "Current Stock" FROM "1-17839-1" WHERE "Avg. trips per mile (×1000)" = 4744.0;

Question: When Green is the map colour what is the future stock?
SQL: SELECT "Future Stock" FROM "1-17839-1" WHERE "Map colour" = 'Green';

Question: When Turquoise is the map colour how many avg. trips per mile (×1000)  are there?
SQL: SELECT COUNT("Avg. trips per mile (×1000)") FROM "1-17839-1" WHERE "Map colour" = 'Turquoise';

Question: When Turquoise is the map colour what is the length?
SQL: SELECT "Length" FROM "1-17839-1" WHERE "Map colour" = 'Turquoise';