Notice quite a few time that it never depart on time.
I've said the reasoning in the eforums.. for the benefit of
everyone i'll reproduce it here.
S57 failed is because on their pm peak trips to bishan they
suffer alot of unforeseen traffic conditions and the schedule
planners had not factor this in ever since goodness knows when. In
addition, their mealbreak times are rather short. Hence, if a bus
arrives late at Bishan but scheduled a 21min mealbreak, the driver
would then have a 20min mealbreak and thus depart late for its next
trip out as well.
S36 failed is also due to city traffic conditions. This causes
buses who arrive late to do 36A as next trip or off service to do
downroute or whatsoever. In any cases, there's lesser trips
departing from Changi Airport.
As for S229 the only reason i can find is the right turn from
NEw Upp Changi Rd to Chai Chee estate, thus having little or no
break and then late departure for next trip.