If you’re like us, one of the worst parts of the Front Range’s annual ozone season, usually at its peak in August, is having to be holed up inside during the final throes of summer. Ozone—a gas and secondary pollutant (so called because it’s created by a chemical reaction where direct sunlight bakes pollutants released by cars, power plants, and other sources together)—can affect our lungs, causing irritation, coughing, and the worsening of respiratory diseases such as asthma.

To combat the region’s increasingly awful ozone problem, the state Legislature passed Senate Bill 22-180 earlier this year to help fund a month’s worth of free RTD fares to encourage people to use public transportation. The program, called Zero Fare for Better Air, kicked off on August 1 and will run through August 31. Although the initiative has its detractors, we figured it couldn’t hurt to go all in on mass transit this month—until we realized leaving the wheels at home could put a crimp in our outdoor recreational style. Fret not: These five adventures, all accessible by either bus or rail will not only save your wallet but also increase the chances the air will actually be clean enough to adventure.

Carson Nature Center and South Platte Park

Riding through South Platte Park. Photo courtesy of South Suburban Parks and Recreation

The D light rail line terminates at the Littleton-Mineral station, just a five-minute walk from this 880-acre open space and education center. Pack a rod: You’ll find smallmouth bass and trout in its five small lakes and in the neighboring South Platte River itself. Man-made rapids also make this stretch of river a popular tubing spot, but be sure to check the water levels first. If you have a bike (they’re allowed on all light rail lines), Chatfield State Park is a 15-minute ride down the Mary Carter Greenway Trail and has 26 miles of paths to explore. Cool off after your ride at the reservoir’s swim beach, open through Labor Day.

Indian Peaks Wilderness

Trail running at King Lake. Photo by Sarah Banks

The NB1 bus line runs from downtown Boulder (get there on the Flatiron Flyer, RTD’s express bus between Denver’s Union Station and the People’s Republic) to Nederland High School. From there, pick up the always-free weekend shuttle to the popular Hessie trailhead, a gateway to the Indian Peaks Wilderness. If you’ve managed to snag a camping permit, you can backpack deep into the wild without ever getting in a car, a rare treat anywhere in the Rockies. If you haven’t, a day hike to Lost Lake or King Lake will still scratch your backcountry itch.

Cherry Creek State Park

On warm summer weekends, there’s almost always a line of cars waiting to get into Cherry Creek State Park, but cyclists can ride right on in for free: The Dayton light rail station, which is serviced by the H and R lines, is a 10-minute pedal from the park entrance on West Lake View Road. There are 35 miles of multi-use trails, but we recommend making it a bi-modal adventure by signing up for a sailing course with Community Sailing of Colorado, which has outings and classes on the park’s namesake reservoir.

Rocky Mountain National Park

Rocky Mountain National Park
Sunrise at Sprague Lake in Rocky Mountain National Park. Courtesy of Esther Lee, Flickr via Creative Commons

Not to be left out, the Colorado Department of Transportation is offering half-price fares this month on its Bustang routes, meaning it costs just $2.50 to take the weekend bus from Denver’s Union Station (get there for free on RTD’s A, B, E, G, N, and W light rail lines) to Rocky Mountain National Park’s Park and Ride Transit Hub (entrance fee required). From there, take the free Bear Lake or Moraine Park in-park shuttles to the final destination of your choice, including Moraine Park Campground, Sprague Lake, and the Bierstadt Lake, Glacier Gorge, and Cup Lake trailheads. If you don’t want to miss Estes Park, you can take the reservation-only Hiker Shuttle from RMNP to its visitor center, where the Bustang will take you back to Denver once you’ve had your fill of the mountain town. (Don’t know where to start? Our Estes Park First-Timer’s Guide has you covered.)

Apex Park

RTD’s W light rail line runs from Union Station to the Jefferson County Government Center (you know, the golden-domed building you see off to the left every time you take I-70 back to Denver from the mountains). From there, it’s just more than a mile and a half to Apex Park. It’s a good warm-up for cyclists looking to tackle the long, sometimes grueling climb through the park to the start of the Enchanted Forest Trail, a fast, root-filled descent that can feel more like riding in the Pacific Northwest than Colorado’s typical moondust. Beware, Enchanted Forest is only open to cyclists on even-numbered days.

Correction: An earlier version of the article featured itineraries that weren’t possible because of RTD schedules. We regret the errors.

Nicholas Hunt
Nicholas Hunt

Nicholas writes and edits the Compass, Adventure, and Culture sections of 5280 and writes for 5280.com.