Usage Limitations
A tunnel is relatively long and narrow; in general the length is more (usually much more) than twice the diameter, although similar shorter excavations can be constructed such as cross passages between tunnels.
The definition of what constitutes a tunnel can vary widely from source to source. For example the definition of a road tunnel in the United Kingdom is defined as "a subsurface highway structure enclosed for a length of 150m or more.". In the United States the NFPA definition of a tunnel is "An underground structure with a design length greater than 23 m (75 ft) and a diameter greater than 1800 mm (6 ft).".
Read more about this topic: Tunnel
Famous quotes containing the words usage and/or limitations:
“Girls who put out are tramps. Girls who don’t are ladies. This is, however, a rather archaic usage of the word. Should one of you boys happen upon a girl who doesn’t put out, do not jump to the conclusion that you have found a lady. What you have probably found is a lesbian.”
—Fran Lebowitz (b. 1951)
“The limitations of pleasure cannot be overcome by more pleasure.”
—Mason Cooley (b. 1927)