This is a great trail that spans 30 miles (one-way), with many different trail heads. It's an easy 5 minute drive from downtown Portland to the close-in trail heads. The trail is marked by blue diamonds on trees every 1/4 mile so you know exactly where you are. If you want to use the trail for a training run, it's probably best to start at mile market 9.25 off of 58th/Cornell Rd. It is flat and very well maintained.