Can you be arrested if you're pulled over for a traffic violation and refuse to provide ID?
The answer is yes -- if the police officer sees you commit the violation and you fail to "furnish satisfactory evidence of identity" (e.g., your driver's license).
The officer has discretion, however, and can choose instead to issue a ticket for failing to display your license on demand, which carries a fine of $50. (This is an option when you have a valid license but don't have it with you, which the officer can determine by running you through the MVA database.)
If you are arrested, the officer can release you if you sign a written promise to appear for trial or must take you before a Commissioner of the District Court for an initial appearance who will determine the conditions of pretrial release.
And be careful. If you don't have a license at all and are caught driving or attempting to drive on Maryland roads, you face 60 days in jail, a $500 fine and 5 points.
Failing to furnish satisfactory evidence of identity isn't the only traffic violation that allows the police to arrest you without a warrant. There are several others as well, which are set out in Maryland Transporation Article Sec.26-202.