Did you use JUMBOLINERS for those intra-town bus routes?
These buses operate with a very high cost (11.XX Cr, compared with some default buses costing of 3.XX Cr)
and they served local routes that earnings cannot recover the cost of operation.
(01) Replace Jumbo-liners by both buses with cheaper operation cost AND mail vans.
Cost Combining both vehicle should be cheaper than these inter-city buses.
(02) Think about to increase service frequencies by using not only ONE, but MORE THAN ONE vehicles, to operate local routes.
[By applying this method, you should also relieve problems like over-crowded stops and fully-packed vehicles at the same time.]
(03) Try to connect factories, curious building spots, EVEN between towns: like we travel as commuters do.
(04) [Optional] To get some cheaper vehicles (in OP cost) from other pak-making fansites.
Japan, Brazil... Shall you know some years ago I have tons of double-deckers available in Pak 64 format - for free.
A Friendly Transfer here: http://www.geocities.ws/nwfb_lv1/download.html
(In Chinese - if you really don't know that language - let Google Translate helps you.)
For the others? Try to have a look in Pak 64 add-on section in this forum, or the read-only Simutrans Forum Archive:http://archive.forum.simutrans.com/board/00039.0/index.html
if you needed some older addon paks for your gaming.
Finally: RETIRE your JUMBOLINERS after new buses start servicing. (Vehicle Details> Retire)
Hope this save some money from depreciation - as time flies, the value of vehicles wear. Cheers!