Running a model train around an attic or basement is too solitary and isolated to appeal to Joel Sherman.

But when he discovered garden railroads - larger-scale model trains for outdoor use - he hopped on the hobby and hasn't let go."I'm having fun," says Sherman, as he presses buttons to activate the whistles and bells on the silver passenger train that snakes around his backyard in suburban Memphis.

Garden railroaders make up only about 10 percent of all model train hobbyists. But their numbers are growing. Garden Railways magazine, the hobby's bible, has increased its circulation from 18,000 three years ago to 33,000 today.

Sherman is one of about 15 members of the Mid-South Garden Railway Society, an organization about a year old.

While there is much pleasure in operating the trains, most outdoor railroad aficionados enjoy planning, building and forever refining their layouts equally.

Though it often takes years to get one operational, Sherman had his two tracks up and running in about six months. Starting in February, he began the first loop around a berm. First he laid a road bed made from numerous pieces of six-inch-wide marine plywood to hold the tracks.

After that was completed, Sherman created a tunnel through the berm and ran more track out from the berm over a trestle to a retaining wall near his tennis court.

Because everyone's backyard is different, there are few standardized materials for tunnels and bridges. Figuring out how to make them is part of the appeal for tinkerers like Sherman.

He read about complicated ways to create tunnels but came up with a simpler idea. A 12-inch heavy plastic sewer pipe proved to be just the right size for tracks and garden rail cars, which are larger than the Lionels most model train fanciers grew up with.

To support the trestle, which is about 2 1/2 feet off the ground, he used electrical conduit.

Once the tracks were laid, it was time to plant and decorate with a train station, store and small figures climbing on flat rocks. On a lower plane is a beach with volleyball players.

Because his railroad is new, the landscaping is still immature. Karyn Sherman, Joel's wife, tends to the moss, sedums and dwarf conifers.

Joel's 14-year-old daughter, Kyra, thought her father's hobby was silly at first, but now she is into building and operating it, too.

"There's more family involvement in garden railroading than any other kind of model railroading," says Marc Horovitz, editor of Garden Railways magazine. "While there are still more males into it, many women are involved on their own."

Partners who may care nothing for the trains will often get into the challenge of selecting, locating and maintaining landscaping plants.

While garden railroading is just taking hold in many places, it is not a new concept.

"It's been big in Europe, particularly England, for over 100 years," says Horovitz.

Before World War II, all model trains were the outdoor variety. After the war, miniaturization became the norm.

"As model trains got smaller and more affordable, they moved indoors," Horovitz says. Then in the late 1960s, a few manufacturers began producing larger-scale trains with outdoor tracks.

Prices have gone down with increased competition, but it is not a cheap hobby. Locomotives will average between $250 and $500 but go as high as $5,000; railcars (or rolling stock, as they are called) cost from $50 to $180 each; power packs without remote control range from $75 to $300; tracks start at $3.50 per foot. Then there are costs for landscaping, remote control devices and buildings.

The equipment is sturdy enough to withstand the weather.

"There's a five-year warranty against everything but your neighbor's Rottweiler," says Dick Wolff, owner of Model Railroad & Hobby Shop in suburban Memphis. He carries lots of supplies for garden railroading, but many hobbyists also buy from catalogs and via the Internet.

Horovitz suggests new garden railroaders read about the hobby and talk to others who are involved before spending a lot of money. "Don't rush in by throwing some track down before doing some research."

Large-gauge equipment isn't absolutely necessary for a garden railroad, says Charlie Tigrett, owner of Dream Machine in Collierville, Tenn. He installed his own garden railroad as well as those for customers using equipment scaled for the Lionel trains many people have stored away in their attics.

His train goes around a large deck, over a small pond and then around a larger one. One of his bridges resembles a Mississippi River bridge in downtown Memphis.

Railroading has been a part of Bill Cooper's life for as long as he can remember. His grandfather, a newspaper distributor and newsstand owner, often took him to the train station in Jackson, Tenn., to pick up out-of-town newspapers. He still has the first Lionel train his father gave him.

"There's a romance to trains you just don't get from airplanes," says Cooper.

When someone gave him a vanload of large-gauge equipment once used in a commercial establishment, Cooper decided it was time to try garden railroading. His outdoor train now runs across a pond on a trestle in his East Memphis yard before making a turn and coming back.

He constructed all of his buildings himself, and built a locomotive using a motor for a model airplane and a propeller. Another of his inventions is a rail car that cleans the track as it travels along it.

"I'm a problem-solver," says Cooper, a graphic designer who also custom-paints simple boxcars for his model railroads.

Garden railroaders never expect to be completely finished with their layouts.

"It's not something you have," says Horovitz. "Garden railroading is something you do."