To jump on the Whittier Greenway Trail (4.7 miles), exit Interstate 605 at Whittier Boulevard. The trail starts at Pioneer Boulevard between Whittier and Beverly boulevards, crosses Whittier, and ends at Mills Avenue and Lambert Road.
The Martin Luther King Promenade is a 1.1-mile strip that runs parallel to Harbor Drive in downtown San Diego. Start at the northern end of the trail, at the Santa Fe Depot. At 5th Avenue, you can make a left off the trail to access the Gaslamp Quarter. The promenade ends at 8th Avenue and Harbor Drive.
The Ojai Valley Trail (91/2 miles) starts at Fox Street in Ojai, runs parallel to Highway 33 and ends in Foster Park, north of Ventura. The Ventura River Trail (6 miles) starts in Foster Park and ends in Main Street in Ventura. The southern trailhead is accessible off U.S. 101 at Harriet and Dubbers streets.
There's no easy way to access the Mount Lowe Railway Trail (31/2 miles). From Loma Alta Drive and Lake Avenue in Altadena, the Sam Merrill Trail climbs 1,500 feet in 21/2 miles to the ruins of the Mount Lowe Tavern. From here, follow the trail marker for the Mount Lowe Road, which climbs 1,200 feet more to Inspiration Point.
Rail-to-Trail operates a virtual rail trail guidebook at http://www.traillink.com.