Breakdown of Sie haben den Abstand einzuhalten.
Sie
you (formal)
haben
to have
der Abstand
the distance (gap, space between)
einhalten
to adhere to
Questions & Answers about Sie haben den Abstand einzuhalten.
How is haben ... einzuhalten different from just using müssen?
The structure haben + zu + infinitive means the exact same thing as müssen (to have to / must). However, it sounds much more formal, strict, and official. You will usually encounter it in written rules, legal documents, or very stern warnings.
Why is zu tucked inside the word einzuhalten rather than sitting in front of it?
The verb here is einhalten (to maintain or keep), which is a separable verb. Whenever a separable verb needs a zu in front of it (like in this obligation structure), the zu gets sandwiched between the prefix (ein-) and the base verb (-halten), squeezing it all into one single word: einzuhalten.
Could Sie in this sentence also mean "they"?
Yes. Because it is the first word of the sentence, it is capitalized anyway. Without more context, Sie haben den Abstand einzuhalten could mean either "You (formal) have to maintain the distance" or "They have to maintain the distance."
Why does the sentence use den Abstand instead of der Abstand?