Signals... 
Trains...
Advantages
- Faster
- Lesser breakdowns
- More user-friendly (announcements)
- More capacity
- Better frequency than buses
Disadvantages
- If theres a disruption,
the whole line would be affected
- Limited routes
- Nosier at times
- Accidents cause serious injuries or death of many
- Breakdowns cause disruptions
Buses...
Advantages
- Can go wherever the roads take
them
- If there's a disruption, the service of the route can carry on as
usual
- Accidents may not cause as much injuries and deaths
- Breakdown buses can be replaced very fast
Disadvantages
- Not very fast
- Not very user friendly unless there's PIS, even though there's
PIS also not very user friendly because there's no audio (Fare
stages may not be understood by passengers)
- Capacity not very high
- Frequency not very good for most services
Well analysed 
Buses do 60, trains do 80/90.
That is the maximum speed. On average is abt 45kph due to the
intervals at stations + deceleration, acceleration...
