S shift driver = peak hr driver. Need to have drivers doing S
shifts, as more buses are used during peak hrs, while less are used
during off peak. So the driver will drive during both peak hrs.
Drivers can go home in between their duty times.
E shift driver = student driver. Many services that are student
based have many of this kind of shift, like 12, 74, 81 etc. they
cater mainly for the student arrival / dismissal times and knock
off during the middle or end of the evening peak hr. this shift
tends to have the longest hours.
T shift is used during weekdays for limited hrs services like 115,
and I think would be used in the upcoming Chinatown services. Many
T shifts on weekends replacing E or S shifts, as weekend demand is
quite flat during the daytime hrs (unlike weekday where demand is
super high during peak hrs, but much lower during off peak).
SBST does take care of its T shift drivers and from what I have
seen they get longer breaks than other shift drivers.