What does "coming right up on" mean in this context?

Question

In "Batman Begins" by Christopher Nolan there is a chase scene in which police are chasing the batmobile. One of the Police officers is talking on the radio to the dispatch, while he is catching up to Batman's batmobile from the back. He says "I'm coming right up on his butt". From the context, I understand that it simply means, that he is "getting closer to the rear end of his batmobile" But I can't find any definition in a dictionary for a phrasal verb like this. The only definition I found, which is similar is:

Come right up: —used by someone (such as a waiter) to say that something will be served or delivered very quickly "I'd like a turkey sandwich and a glass of lemonade, please." "Coming right up!" (source: Merriam Webster)

I even thought these are two phrasal verbs combined together, consisting of "come on" & "right up". Can someone provide a definition for this phrase?

Answer 1

I think that you missed the correct definition of "right". M-W gives two that could work here:

2: in the exact location, position, or moment : PRECISELY
// right at his fingertips
// quit right then and there

4: in a direct line, course, or manner : DIRECTLY, STRAIGHT
// go right home
// came right out and said it

"Come on" is not a phrasal verb here. "On" is a normal preposition, with the following definition:

c—used as a function word to indicate position in close proximity with
// a village on the sea
// stay on your opponent

Answer 2

I think you're almost right and that it would be easier to understand this as using 'right' (directly, exactly) to modify the phrasal verb 'come up' in combination with the idiom of being 'on someone's tail' (or, in this case, butt).

'come up' in the second sense linked here as in to approach / get closer to. https://www.merriam-webster.com/dictionary/come%20up

https://www.merriam-webster.com/dictionary/on%20someone%27s%20tail