Dear Akiva,

Basically forbidden. See Mishna Brura 349:16,17.

There are 3 times it is permitted only if all conditions are fulfilled (see yourself): someone still on the road and Shabbos entered see 266:15-19, what's considered stopping, what about changing to a different Reshus, etc.

Also, finding Tefillin laying in disgrace, 301:155-159, and moving dangerous "thorns", 308:75-79.

All the best,

Reuven Weiner