Maryann Romero happily left her car at her Brickell Avenue condo to go shopping downtown the other day, an urban outing made possible only recently with the launch of the city of Miami’s free Brickell-Biscayne trolley-bus line.

Romero rode the throwback-style trolley bus through the bustle of downtown and the financial district, the happy-hour crowds at Brickell Village and joggers on Brickell Key. A mom picked up her son at Southside Elementary, domestic workers took the trolley to the Brickell Metrorail station, and office workers hopped on for a few blocks to shorten the walk home on a drizzly afternoon.

For people who, like Romero, live and work in and around downtown, the new trolley is only a small taste of what’s to come. From taking trains to planes, from riding bicycles or sleek, fast buses to the far corners of Miami-Dade County and beyond, nothing less than a multi-modal transportation revolution is in the offing for Miami’s urban core, and none of it involves private cars.

On July 28, the new Metrorail Orange Line to Miami International Airport will begin service, for the first time directly linking downtown by train to the principal portal to the city for millions of travelers.

And in as little as five years, assuming all plans pan out, downtowners and commuters also will be able to:

•  Jump on a new, privately run All Aboard Florida passenger train and, having dined on a gourmet meal, arrive in Orlando in three hours, far less than it takes to drive;

•  Ride Bus Rapid Transit — hybrid double buses with preferential right-of-way — to west Miami-Dade on State Road 836, or all the way up Biscayne Boulevard to Aventura, or along 27th Avenue to the Broward County line. The buses can beat traffic because they turn traffic lights green as they approach, make limited stops at elevated stations for fast boarding, and travel on expressway shoulders and express lanes;

•  Stay close to home and circumnavigate downtown, Brickell and outlying urban districts on a network of free trolleys, a cleaned-up, improved Metromover system, or on a bicycle or Smart car rented on the street with the swipe of a card.

Already, apart from two new city trolley routes, some smaller-scale launches have expanded the transportation alternatives for commuters and the growing number of people who call downtown home.

Miami-Dade transit has been running well-used express commuter buses to Broward from downtown for two years. Its counterpart in Broward just launched its own version, connecting Sunrise with Fort Lauderdale and downtown Miami along the express lanes on Interstate 595 and I-95, and is reporting high ridership.

And Tropical Pedicabs, a startup by a group of young entrepreneurs, is running five pedal-powered passenger trikes from Mary Brickell Village to downtown Miami and out to the Miami Marlins stadium.

The panoply of launches and planned transportation options, a combination of private and public initiatives, is a response to two realities, backers say: The collapse of costlier plans for Metrorail expansion, high-speed intra-state rail and a city light-rail streetcar line, combined with an explosion in downtown population and activity that makes providing alternatives to the private automobile not just necessary, but feasible.

“We live in a maturing city,’’ said Albert Sosa, Miami’s chief of capital improvement projects. “We’re becoming a lot more urbanized and cosmopolitan. And as we become more urban, it better lends itself to transit.’’