single
n.— «Bike trails are commonly known as “singles,” because they constitute narrow trails just wide enough for a single bicycle bearing one rider. Bikers ride in a single file and blend in with nature and the topography surrounding them. » —“Bicycle races are coming your way” by Danit Nitzan Haaretz (Israel) Oct. 30, 2007. (source: Double-Tongued Dictionary)
Further reading
Some people work hard to lose their accent in order to fit in. Others may be homesick for the voices they grew up with and try to reclaim them. How can you regain your old accent? Also, a compelling book about scientific taxonomy shows how humans...
It was a dark and stormy night. So begins the long and increasingly convoluted prose of Edwards Bulwer-Lytton’s best-known novel. Today the annual Bulwer-Lytton Contest asks contestants for fanciful first sentences that are similarly...
never heard it called “singles”; usually it is “single track”.
more than you want to know:
<http://www.isu.edu/~nickbenj/bike/mtbdic.htm>
FWIW, here on the west coast we call “fire roads” what people on the east coast call “dual track”.