A new study shows the number one alternate fuel among fleet vehicles is biodiesel. The National Biodiesel Board says the study by The Association for the Work Truck Industry shows biodiesel is now the most commonly used alternative fuel option on the market. Survey data shows 18 percent of fleets use biodiesel, up from 15 percent in 2015. The survey was conducted in December and results were released this month. The results find that regarding future alternative fuel interest, biodiesel also takes top honors, with more fleets planning to acquire or continue using biodiesel than any other alternative fuel option.