Burlington International Airport: BTV is in neighboring South Burlington, roughly 3–4 miles from downtown. The sensible default is Uber/Lyft or a taxi: about 10–15 minutes and roughly $15–25 before surge/tip. Green Mountain Transit’s airport service (commonly Route 11) can be a cheap or fare-free alternative when its schedule matches your flight, but it is not frequent enough to treat as an airport express; check the live GMT timetable.
Burlington Union Station: This is the downtown terminus for Amtrak’s Ethan Allen Express from New York via Albany, Rutland and Middlebury. It is the rare station transfer that needs no transfer: Church Street is a 10-minute uphill walk; most downtown hotels are walkable. A rideshare to the waterfront/core is only a few minutes if you have bags.
Essex Junction–Burlington Amtrak station: The Vermonter stops here on its St. Albans–Washington, DC route. Essex Junction is about a 15-minute drive east of downtown, so use a pre-booked taxi/rideshare (roughly $20–30) unless a GMT bus schedule happens to work. Do not assume there will be taxis waiting at the platform.
Downtown Transit Center / University Place intercity-bus stops: Greyhound uses the Downtown Transit Center, at Church and Cherry streets, which is already in the center of town. Megabus’s University Place stop is near the UVM/medical-center edge of downtown: walk 10–15 minutes downhill to Church Street, or take a short rideshare if carrying luggage.