trolley line 架空线
trolley line[ noun ]
a transit line using streetcars or trolley buses
<noun.artifact>
Trolley car \Trol"ley car\ (Elec.)
A motor car powered by electricity drawn from a trolley, and
thus constrained to follow the trolley lines.
[Webster 1913 Suppl. +PJC]
{Trolley line},
(a) A trolley
(f) .
(b) The path along which a trolley car runs.
[PJC]