Using 乗る as a passenger

Question

When I first heard of "自転車に乗る" in a song, I thought it was about riding on a bicycle instead of riding a bicycle, because of the kanji "乗." Then, I realized that 乗る does not only mean riding as a passenger, e.g. "電車に乗る," "taking a train ride."

For example, there is also

「飲んだら、乗るな。乗るなら、飲むな。」

This tells me that 乗る can be used to mean "operating a vehicle," or, in the case of a bicycle, to ride one.

However, is it possible that "自転車に乗る" also means "to ride on a bicycle," or do I have to say something like "(私は)自転車に乗られる"?

If I want to specify riding in/on something as a passenger as opposed to 運転する, how do I go about this using 乗る, or is there a different verb/expression involved?

For instance, how do I say something like, "My friend's giving me a ride to the park on his bicycle now"? Given my rather limited Japanese, I can only think of:

今(僕は)友達が乗ってる自転車で公園に行ってる。

This is quite a mouthful, if not unnatural. Nonetheless, if this works, does it apply to cars and other vehicles as well?

今(僕は)友達が乗ってる宇宙船で木星に行ってる。

いつもお世話になっております。ご教授お願いいたします！

Answer 1

(<乗り物>に)乗る is an unspecific verb that basically says nothing about whether you're a driver or a passenger. Imagine how people usually use that vehicle/boat/etc. 自転車に乗る usually means riding a bicycle, but it can be used regardless of whether you're holding the handlebars or not.

Of course 乗る in 飲んだら乗るな only refers to driving a car, but it's a well-known rhythmical slogan which everyone should understand without explicit 運転. 電車に乗る said by a layperson safely means getting on a train as a passenger, because everyone understands that most people do not operate a train.

how do I say something like, "My friend's giving me a ride to the park on his bicycle now"?

This is a good chance to use もらう: 「友達の自転車に乗せてもらって公園に行っている。」

自転車に乗られる means "I am mounted by a bicycle", which makes almost no sense.