众所周知，交通信号灯（traffic lights/ traffic signals）有“红灯停，绿灯行（The green light allows traffic to proceed. The red signal prohibits any traffic from proceeding.）”之说。
“开绿灯”指交通路口打开准许行人车辆通过的信号（give the go-ahead signal，give the green light），后多用于比喻“允许某事（allow someone to do something or something to happen）”，或“提供方便条件（make easier for）”。
- 官僚主义总是为腐败大开绿灯。
Bureaucracy always gives the green light to corruption. - 我们永远不会给赌博开绿灯。
We'll never give the green light to gambling.
