The usual study/reference for this is someone biking at ~10mph. Bicycles become progressively less efficient at higher speeds due to air resistance. Fairings a

The usual study/reference for this is someone biking at ~10mph. Bicycles become progressively less efficient at higher speeds due to air resistance. Fairings and reduced frontal area (recumbent/supine positioning) can help this considerably. The combination is commercially sold as velomobiles and they're not especially popular but they do work. As an example, dedicated amateur enthusiasts do 3 hour century rides in commercial velomobiles regularly.