Joker lah you... You think give thumbs-up means like the bus
meh? 
You look around, they just generally give thumbs up to ask how is
the other driver. If everything is okay, the other driver give back
thumbs-up.
Or in 179 case, if the driver chiong and overtake many buses until
his bus empty and very happy, he will show off give thumbs up to
every driver he sees... 