Allegheny County Parks Director Andy Baechle and the Pittsburgh Trails Advocacy Group know how to organize a ride.

One of their best is being offered today at Boyce Park -- two others were Saturday at North Park and yesterday at the Bavington Gamelands. The free rides, each of which cover 12 to 15 miles in about two hours, are for riders of all abilities. They are part of the fourth annual Allegheny County Mountain Bike Festival.

Today's Boyce Park ride begins at 6 p.m. at the soccer fields near the Park shelter. It will be led by veteran cyclist Barry Jeffries, assisted by other ride leaders.

Participants are expected to have a knobby-tired mountain bike in good riding condition, a helmet and water.

PTAG board member Mike Connors said the Greater Pittsburgh area has some of the best spots for mountain biking in the country, many of which are within an hour's drive from Downtown.

He said, in addition to North and Boyce parks, they include Frick Park, Riverview Park, Schenley Park, South Park, Settler's Cabin, Hartwood Acres, Harrison Hills, Deer Lakes, Apollo, Brady's Run, Moraine state park, the Laurel Highlands and Seven Springs.

Baechle said the festival is designed to "reach out to the growing number of cyclists and acquaint them with the trail systems available in our county parks. We are pleased to partner with [PTAG] on this exciting endeavor, and we encourage anyone who likes mountain biking to come out and enjoy what our parks have to offer."

And what the parks have to offer mountain bikers is considerable, thanks to the efforts of Baechle, parks department employees and the multi-talented members of PTAG who have donated thousands of hours to build and maintain a variety of multi-purpose trails for bikers, hikers and equestrians.

A typical PTAG "big" work day is held once a month and usually consists of three hours of work, three hours of riding and three hours of picnicking.

During a three-hour work session on a Sunday at Boyce Park in August, 51 PTAG volunteers assembled a 24-foot-long wooden bridge, installed a culvert, cleared a debris-choked stream and improved hundreds of yards of trail.

"We got a lot done thanks to all the PTAG members who donated their time on a beautiful Sunday when they could have been sleeping in, reading the newspaper or just taking it easy," said Jeffries, who organized the project.

Festival participants are encouraged to bring a snack or covered dish to share with their fellow riders and then to take advantage of the pools, picnic shelters, free concerts and other recreational activities and amenities available in the parks.

PTAG was formed in 2001 to protect and encourage shared-use access to the trails in Western Pennsylvania. It works with city, county, state and private landowners to ensure that all trails are approved, constructed and maintained to International Mountain Biking Association standards and have minimal impact on the environment.

For more information on the festival, go to www.alleghenycounty.us/parks/bike.aspx. For more information on PTAG, a non-profit organization, go to www.ptagtrails.com.

Connors said the Over the Bar Bicycle Café on the South Side is helping to host this year's festival.