It is 6:22 a.m. on a July day and traffic is already heavy on one of Tucson's main east-west routes.
But there's not a car in sight.
This thoroughfare - the Rillito River Park Trail - is the exhaust-free domain of people moving under their own power: walkers, cyclists and runners.
The trail is often busy early on summer mornings with beat-the-heat exercisers, but it's been especially valuable in recent weeks with national forest trails closed due to fire danger.
Extending from North Craycroft Road to Interstate 10, the Rillito trail is part of an expanding network of trails along watercourses.
Try any segment for a short, brisk workout. Link paths together for a longer excursion.
GO WITH THE FLOW
Here are some other watercourses - occasionally flowing with storm runoff, but usually dry - where trails trace the stream bank.
• Santa Cruz River - A trail extends from West Grant Road to West 29th Street, with another section between West Irvington Road and West Ajo Way.
• Pantano Wash - A new trail segment extends from Kenyon Drive southeast to Michael Perry Park. Kenyon Drive is north of 22nd Street, and Michael Perry Park is south of Golf Links Road. More additions are in the works.
• Tanque Verde Creek - A popular segment extends east along the creek from North Sabino Canyon Road.
Entry points at major street intersections allow access to the trails for walkers, runners and cyclists.
An urban loop connecting several of the trails eventually will total 55 miles.
• You may visit parks anytime from dawn to dusk - but it's best to head out very early in the morning in the summer to limit heat problems.
• Stay in proper travel lanes and be courteous to others.
• Dogs must be leashed at all times.
Contact reporter Doug Kreutz at email@example.com or at 573-4192.