loop tunnel

loop tunnel

[′lüp ‚tən·əl]
(engineering)
A tunnel which is looped or folded back on itself to gain grade in a tunnel location.
References in periodicals archive ?
Musk's company has also proposed a Loop tunnel that would run between Washington, D.C.
Premier Denis Napthine said, "For the first time, metro rail passengers, through their mobile phone carrier, will have high-quality mobile coverage throughout the City Loop tunnels and its underground stations.
This will ensure that Melbourne s City Loop tunnels and underground stations will be mobile phone friendly.