Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_38454 ( "Line" text, "Speed" text, "Length" text, "Construction begun" text, "Expected start of revenue services" real )

### Question ###
What is the length when the expected start of revenue is more than 2017?

### Accurate SQL ###

SELECT "Length" FROM table_38454 WHERE "Expected start of revenue services" > '2017'