Many cities are plagued by bus bunching at peak hours: one bus stops frequently to pick up and drop off passengers, slowing its progress. The bus behind it, finding stops cleared, goes increasingly fast, until the two meet.
It’s not unusual for three or four buses to collect this way,
frustrating riders who have to wait increasingly long intervals for a
bunch of buses to arrive all at once.
The traditional solution—for the second or third bus to pull over and
idle at the curb for several minutes—frustrates riders even more.
Emerging technology may offer a better solution.
Busting Bus Bunching With Traffic Signals - Forbes