請問I travelled yesterday for four hours in a train. It's a funny sensation, isn't it? I never rode in one before這句中in a train和in one為什麼不用on?

I travelled on the train for four hours yesterday.
I have never ridden on one before.

ride, rode, ridden(pp)
in a train=adverb--The train is in.
The train isn't in yet.
I never rode in one before
=such one---so great , so good, 
It was so funny,excited and sensational
=It was such a funny, sensational ride.
=The riding was funny and fast and sensational.
=The sensational condition for riding on, rode across and travelling along.
=eg:-I have never ridden on one by "one" such before.
=eg:-I have never ridden on one such before by "one".
on adv adj----The train stopped,and we got on
=(into the train)
="One" was ridding on on the train
=I was ridding on the train...
=I travelled on the train for 4 hours yesterday.