The health impacts valuations presented in the study come from national benefit per ton figures developed from a Community Multi-scale Air Quality (CMAQ) model, which is regularly used in EPA Clean Air Act rulemaking.
And what ambitious scale it is: each horse sculpture can weigh anything up to a ton (1, 000 kilograms), is 16-17 hands (around 5ft 11ins) tall and can easily take the weight of a "jockey" or two.