These are both infinitive markers.
Student or Learner
"I want to cry."
"I'm used to driving."
How do I know the difference between "to" as the infinitive marker and "to" as a preposition?
***** NOT A TEACHER *****
"Be used to can be followed by nouns or -ing forms (NOT infinitives)."
-- Michael Swan in Practical English Usage (1995), entry 578 on page 605.
Mr. Swan gives this example: "It was a long time before she was completely used to working with old people."
Mr. Swan reminds us that "used" in this structure is an adjective.
Therefore, I believe that we can reasonably conclude that "to" is a preposition in that sentence.
Last edited by TheParser; 30-Nov-2014 at 14:43. Reason: spacing