How to make a remote internet connection more reliable?

I’ve got a client that owns a stretch of railroad 42 miles long. One train leaves Biloxi traveling eighteen miles an hour…

(no, this isn’t a story problem)

Okay, but there is a long railroad track. That’s just background, though, and isn’t all that important at the moment.

There are some locations along these tracks that have some hardware that reports telemetry and video back to a central server on a continuous basis. In a few places cable internet is available, in most it has to be DSL.

They’ve accepted the upstream bandwidth limitations on the DSL and the cable. However, the connections appear to be completely unreliable. I’m talking a downtime of at LEAST 30% if not a whole lot more.

Surprisingly, AT&T and CableOne claim their stuff is just 100% and it can’t possibly be anything to do with their connections. Yet somehow I’m having the problem whether I try to access this stuff from my office or the railroad’s. Does anyone have any tricks to try to convince a DSL connection to be more stable? Modem settings to make them less likely to drop? Anything?

-Joe