which one is correct- Let's go on a bus/go in a bus/ go by a bus?

Question

which one is correct- Let's go on a bus/go in a bus/ go by a bus ? I am confused with these three options.

Answer 1

When we're speaking of the mode of transport and not a specific vehicle we omit the article: "Let's go by bus", just like by {horse / train / car / airplane / boat / bicycle}, &c.

With most vehicles we use on when speaking either of location or the goal of movement:

LOCATION: I left my laptop on the { horse / bus / tram / train / airplane / boat / bicycle}.
GOAL: I got on the {horse / bus / tram /train / airplane / boat / bicycle}.

With automobiles/cars, however, we use in:

I got in the car.
I left my laptop in the car.

Railroad and tramcars usually take in for goals but either in or on for location.

Trucks swing both ways.