According to Bikes Belong:
Green lanes are dedicated, inviting spaces for people on bikes in the roadway, protected by curbs, planters, posts or parked cars. The goal of the Green Lane Project is to support the selected cities in their efforts to develop and install these kinds of facilities. Recent studies have demonstrated their benefits nationwide. In Washington, D.C., bicycle volume tripled after protected lanes were installed. In Portland, Ore., more than 70 percent of survey respondents said bicycling is easier and safer with these dedicated lanes, while motorists said the facilities did not make driving any slower or less convenient.
Read Ray LaHood's blog post: