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_171748_3 ( period VARCHAR, _percentage_trains_arriving_within_5_mins_of_scheduled_time_moving_annual_average__maa_ VARCHAR )

### Question ###
When was the percentage of trains arriving within 5 minutes of scheduled time 89.6%?

### Accurate SQL ###

SELECT period FROM table_171748_3 WHERE _percentage_trains_arriving_within_5_mins_of_scheduled_time_moving_annual_average__maa_ = "89.6%"