There was a study done comparing the efficiency and pollution characteristics of using cargo electric bicycles vs. vans in an urban environment. While the cargo capacity of a van is more than that of a bicycle there were some surprises. The drop in pollution was not a surprise but time saving because of what a bicycle could do in a congested environment was a surprise.
Clearly this would not give you the same result in an urban environment but the results were pretty amazing in the middle of a city. The study is discussed in this video
