Preposition for transport IN/ON/BY

Prepositions are always a difficult task for English learners because they usually don't have any rules that one can memorise and use all the time without any exception. That's why here I'm, going to share a few rules for transport and travel prepositions that work 100% of the time.
let's learn with examples -

(a) Ashok is in the bus.
(b) Ashok is on the bus.

Now which one is correct or more appropriate in the above sentences(a) or(b), take your time and think.

Most of us think that sentence(a) is correct but it is wrong. sentence (b) is grammatically correct.

ON

ON is used for a vehicle where we can stand and walk like a bus, train, plane, ship e.t.c.

• He was reading a book on the bus.
• My mother rang me when I was on a train.
• I can't talk to you because I am on a plane.

we use ON for two-wheeler like a bike, cycle, motorbike e.t.c.

• Amar can't talk because he is on a bike.
• He was on a cycle when a car hit him.

IN

IN is used for a vehicle where we can only sit not even stand properly like a car, truck, taxi, cab, helicopter, e.t.c.

• He was in a helicopter when it was crashed.
• she is in a van.
• Riya waved her friends in a car.

BY

BY is used for describing the mode of travel like by bus, by car, by taxi, by cycle, by train, by motorbike, by air, by sea, by road, e.t.c.

• He is used to travelling by air.
• My aunt came to my home by train.
• Jeck reached to Japan by sea.

At last, I have an error for you

(a) It takes two hours to reach here in foot.
(b) It takes two hours to reach here on foot.

Drop your answer in the comment box, which sentence is a right between (a) and (b).

I hope you understood how to use common preposition(in/on/by) for transport and travel.