The Air Tram concept is a simple development of the public transportation systems which have been in use within Human society for millennia. This particular model was designed to operate purely within planetary atmospheres, carrying small groups of passengers on trips of a few miles - generally within the boundaries of a single city, where transporter systems were still too energy expensive for wide scale use by the public. The tram was built in large numbers and was a common sight on Earth in the 2260's. Eventually, however, improvements in the efficiency of transporters began to seriously affect the air trams competitiveness. By the early 2270's air tram numbers had fallen rapidly, and by 2280 this type of craft was no longer in civilian service.
In 2259 Starfleet procured a number of air trams for use in and around sensitive ground facilities which operated continually under transporter inhibitors. These continued in service well beyond the point at which civilian models had become impractical - some were to be seen still operating as late as 2285. In the late 2280's Starfleet switched to inhibitors which blocked only non-Starfleet transports, and the air tram was finally phased out of service for good.