How many lengths of line 3 are given?
CREATE TABLE "table1_1603807_2" (
  "line" text,
  "terminals" text,
  "status" text,
  "length" text,
  "total_number_of_stations" real,
  "operator" text
);
SELECT COUNT("length") FROM "table1_1603807_2" WHERE "line"='Line 3';