The DMG gives rules for chases starting on page 252, and includes
"During the chase, a participant can freely use the Dash action a number of times equal to 3 + its Constitution modifier. Each additional Dash action it takes during the chase requires the creature to succeed on a DC 10 Constitution check at the end of its turn or gain one level of exhaustion."
Class features that grant Dash as a bonus action, such as a Monk’s Step of the Wind or (possibly, see below) a Rogue’s Cunning Action could allow a character to take the Dash action twice in their turn (once as a main action, once as a bonus action).
Would two uses of Dash in the same turn both count against the number of "free uses" of Dash during a chase?
Since the Con check is made "at the end of its turn", would two Dashes made in the same turn require one Con check or two at the end of the turn? If two checks can both happen at the end of the turn, are they resolved simultaneously or sequentially? (For example, the first failed check would apply a level of exhaustion, which would cause disadvantage on ability checks – but would this disadvantage apply to the second check, if both checks occurred at the "end" of the turn?)
The rules for a chase say that "As in combat, each participant in the chase can take one action and move on its turn." Since a chase is run "as in combat", does this allow a rogue, whose cunning action explicitly can be used only in combat, to use cunning action in a chase as well?