From the Wikipedia page for the Pneumatic tube:
Denver International Airport [DEN] uses many pneumatic tube systems, including a 25 cm diameter system for moving aircraft parts to remote concourses, a 10 cm system for United Airlines ticketing, and a robust system in the parking toll collection system with an outlet at every booth.
The article lacks a citation and their are few credible references on the web. There is a 1994 Wired article with this sentence:
Systems like the one just installed by Denver's Translogic Corp. in that city's new international airport - its 10-foot-diameter tube whisks around airplane parts weighing up to 17 pounds - seem to be pushing the practical limits of pneumatic tube systems.
Question: If these systems actually exist, what are their total lengths (eg. 35 km total) and usage rate (eg. 7000 objects per day)?
Note: The original question was posted (in a shorter form) at Aviation Stack Exchange last year by user Nicolas Raoul. No answer has yet been provided.