Multiple realities(covers information from several alternate timelines)
A garbage truck was a type of truck that was used in late 20th century Earth. Garbageman would collect trash, which they then put into this vehicle for a trip to a disposal site.
In 1986 San Francisco, these trucks were owned and operated by the San Francisco Department of Sanitation. (Star Trek IV: The Voyage Home)
By the 23rd century, there were garbage trucks capable of flight, called garbage barges.
In the alternate reality in the year 2259, when Spock was pursuing Khan on the streets of San Francisco, he fought him on top of two flying garbage trucks of that type. (Star Trek Into Darkness)