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_1817879_2 ( line_s_ VARCHAR, segment_description VARCHAR )

### Question ###
How many lines have the segment description of red line mos-2 west?

### Accurate SQL ###

SELECT line_s_ FROM table_1817879_2 WHERE segment_description = "Red Line MOS-2 West"