They were also crossed with Hackneys and Thoroughbreds. At least one park placed an order for a fleet of Hackneys. When the Hackneys refused, Davis ceased his support. These tracks eventually reached the younger Hackneys, who instantly recognized their father's voice. Many hackneys also have some white markings. Common riding horses, often called "hackneys", could be used as pack horses. Both taxis and hackneys are licensed by the National Transport Authority. After 1662 hackneys were regulated by the Commissioners of Scotland Yard. The Hackneys have an average length of back, muscular, level croups, and powerful hindquarters. Hackneys have been exported into Australia, the United States and the Netherlands. Hackneys often have white markings, often due to the influence of sabino genetics.