  In continuation to an earlier work, where error exponents of typical random
codes were studied in the context of general block coding, with no underlying
structure, here we carry out a parallel study on typical random, time-varying
trellis codes for general discrete memoryless channels, focusing on a certain
range of low rates. By analyzing an upper bound to the error probability of the
typical random trellis code, using the method of types, we first derive a
Csiszar-style error exponent formula (with respect to the constraint length),
which allows to easily identify and characterize properties of good codes and
dominant error events. We also derive a Gallager-style form of this error
exponent, which turns out to be related to the expurgated error exponent. The
main result is further extended to channels with memory and mismatch.
