Much like a smartphone, your body will go to sleep when there are no new inputs.
When you are on a bus, your senses will give you the same repetitive inputs. The streets will flow by, the AC and engine adds constant white noise, you're seated and not moving, and the smell... well you hope the smell doesn't change.
Any repetitive input going to your brain will eventually be ignored and your brain will start going into a low energy state. The fact that you fall asleep quickly when closing your eyes on a bus is because you were already on the bus for a while and got used to all the repetitive sensory data.
When you go to bed, you have a lot of new changes. You are lying down, you wear different clothes, you feel the pressure of your covers, you go from bright to dark, noisy to quiet. All of these arenew sensory inputs that your brain needs to get used to before going to sleep.
This is, to our knowledge, the first study to investigate the effects of whole-body vibration on seated human alertness and drowsiness. Our data clearly demonstrate that exposure to vibration has considerable influence on subjective sleepiness levels, and more importantly, human reaction times and lapses of attention.
These findings need to be further consolidated particularly in relation to driving behavior (steering entropy). This line of research can then assist in the development of practical and relevant guidelines for limitation of vibration exposure in the automotive industry, in an effort to reduce the burden of road accidents.
That's something for both car manufacturers and road safety experts to think about.
Carve out at least 30 minutes of wind-downtime before bed in which you do something relaxing, such as read a book. Dim the lights in the house slightly for an hour or so before bed.
Disconnect from close-range electronic devices such as laptops, phones, and tablets, as the light from their screens can alert the brain and make it harder to fall asleep.
To calm your mind, do a breathing or relaxation exercise.
If you get into bed and cannot fall asleep after 20 minutes, get up and return to another space in the house to do a relaxing activity, such as reading or listening to music. Lying in bed awake can create an unhealthy link between your sleeping environment and wakefulness. Instead, you want your bed to conjure sleepy thoughts and feelings only.
Wake up at the same time every day. Even if you have a hard time falling asleep and feel tired in the morning, try to get up at the same time (weekends included). This can help adjust your body's clock and aid in falling asleep at night.