A quarter mile siding may still be quite useful, depending
on its purpose. Main line passing sidings now tend to the in
the two-mile length range -- assuming that there are no terrain
features that would make that length difficult to build.

But there are also "work" sidings that can be used for a variety
of purposes, other than trains meeting or overtaking each other.

Among possible uses of shorter sidings are the setting out of
bad order equipment, the storage of cars that are not immediately
needed, the storage of MoW equipment (a quarter mile rail train
will still fit into a quarter mile siding if the siding is actually
slightly longer than a quarter mile), and a variety of other uses.

Short sidings can be used by locals to run around their cars or
to do some basic sorting of cars into a particular sequence.

In some cases through freights will set out cars that are destined
for nearby industries into a short siding. A local then comes
along and picks up the cars and does the final switching. The
local may then leave cars in the same siding for the next through
freight to pick up.

Or, a local based at A may work a section of mainline through C.
On its way out, it may have picked up some cars between A and B.
As the cars will ultimately need to be taken back to the yard at
A, there is really no sense to haul them all the way to C. So, it
may leave some cars in a siding at B, while it continues on to work
additional customers between B and C. On the way back, it will
collect the cars left at B. Switching is a lot simpler if you
don't have so many cars with you.

-- Ernest