INDEX and MATCH functions to sum data with blank cells

Hi everyone,

I am looking for a formula that will work with the attached data set. What I want to be able to do is create a formula that is fully automated -- I need a formula that would basically say this for example: IF "6 Carter Finley" (column A), AND "Carter-Finley Park & Ride" (column B) THEN add all on-time departures (column S) that meet that criteria. So the end result would be a formula that would tell me the sum of all on-time departures, at the Carter-Finley Park & Ride, for the 6 Carter Finley.

I think the trouble I am having is two things -- the routes repeat through the table and there are spaces. I would also like to build the formula so I wont have to manipulate the raw data at all -- basically just copy and paste it in -- so the list would be a placeholder like "A1:A10000" (because the number of rows may vary from time to time). The route ordering changes from time to time, so for example "6 Carter Finley" wont always be in A51 each month.

I've searched the boards and founds tips on using INDEX and MATCH (including using ISBLANK), SUMIFS, SUMPRODUCT, etc. I've also done the cntl-shift-enter function to make the formula an array function but it is still giving me errors.

Please see the attachment and let me know if you all devise any formulas that work with my data. Thank you!!