Driving down e riding down - Tradução em português

Hi guys, I have a question. Why sometimes riding down means descendo and others no. In the same way can you explain to me how recognize the correct meaning? For example.

He is riding down Juca's Street. In this example means descendo.

Buut...if the statement is: While driving down the Street...what's the meaning?

Well i don't know when the word down refers to "descer"...



That's it!