The Phone Line trail in Sabino Canyon is as straightforward as it gets. This trail follows the southern side of the tram road up into and along Sabino Canyon, albeit several hundred feet above it. It's a nice distance on an easy to follow trail with great views up into Sabino Canyon all along the way. This trail is also popular with trail runners as it is fairly level after the initial elevation changes at either end.
To reach the beginning of the Phone Line Trail you start out from the Sabino Canyon Visitors Center following the Bear Canyon Trail, which begins at the eastern corner of the parking lot, to the right of the visitors center. This first section follows a wide dirt track, formally a shuttle road, till it reaches a paved section of road. Turn right on the paved road, and follow it downhill to another intersection, next to a building containing restrooms. Here, you'll turn right again, and follow the road across Sabino Creek and uphill to the last intersection. Straight in front you, the Phone Line trail leaves the road (at a small sign announcing it's departure) and climbs a short distance up to the spine of a ridge where it splits. To the right the Bear Canyon trail heads off toward Seven Falls. To the left, the Phone Line Trail heads gently up the ridge on it's way into Sabino Canyon. Turn left here and formally begin your journey.
Initially the trail gains elevation and heads towards the western flank of Blackett's Ridge. After a little over one-half a mile a sign marks the beginning of the Blackett's Ridge trail to your right. The Phone Line continues onward to skirt th the western edge of the ridge, then eventually curves north, then east around it to start it's northeastern trek into Sabino Canyon.
As you round the bend, great views up into Sabino and the Catalina high country will be your guide the rest of the way. You can also see the tram road climbing up the canyon as well. You are now hundreds of feet above it, you can see little specks (people) cruising along the path. Thimble peak and Blackett's Ridge are up and to your right. As you pass these, new peaks guide you further into the canyon. The going is easy. Multiple large rock outcroppings on your left along the way provide good sites to have lunch. As you finally reach the end of the line, the trail starts switchbacking down. You can see the circular turnaround beneath you for the trams. Switchbacking down, the Phone Line meets up with Sabino Canyon trails (which continue up the canyon). Continue downward to the road. Enjoy nice views, then reclimb and begin your trip back. Alternatively, for those inclined, you could always catch the tram back to the visitor center. If you choose to walk to and from the formal beginning of the Phone Line trail plan on adding about 2 miles to your total trip length, bringing the whole hike to about 11 miles or so.
This is by no means a secluded hike, but it's a nice stroll along the upper walls of Sabino Canyon nonetheless. It's also kind of neat to tower hundreds of feet above the walkers and trams patrolling the roadway. As a side note, this trail is popular in Tucson for runners. If you encounter any, be courteous and give them the right of passage.