There is some light traffic, and the road can be muddy in wet weather; private land borders both sides of the road.
When you are tired of winter rides on the Boise Greenbelt, but the trails higher in the foothills and mountains are not yet ready for prime time, you can get a light workout along Pearl Road. It starts just off of Hwy 55 (ironically its called Spring Hill Road, on the left as you climb up Horseshoe Hill out of Eagle). The road is lightly maintained, so it can give a good impression of a mountain trail.
The road's scenery is modest foothills with wildflowers in early June. After June, save this ride for fall, or a sunrise cruise as there is no shade and you'll absolutely bake. About five miles in you'll reach what's left of the ghost town of Pearl. It's really just a few jumbled ruins and a curious mine opening - probably the only mine shaft in the world that features an old automobile as its entrance roof.
After Pearl there is a nice long downhill cruise towards Eagle. You can stop once you reach the valley floor, or head further down into the town of Eagle. Many of the roads that you see on the map are private easements. Just remember the long uphill ride back; it's not terribly tough, but it goes on for several miles. Strong beginner riders will be fine as long as you let everyone catch their breath once in a while.
The return trip features a lovely view of the foothills and the mountains of Bogus Basin. It may be what Boise looked like before there was a Boise.