  Cellular automata have turned out to be important tools for the simulation of
traffic flow. They are designed for an efficient impletmentation on the
computer, but hard to treat analytically. Here we discuss several approaches
for an analytical description of the Nagel-Schreckenberg (NaSch) model and its
variants. These methods yield the exact solution for the special case $\vm=1$
of the NaSch model and are good approximations for higher values of the
velocity ($\vm > 1$). We discuss the validity of these approximations and the
conclusions for the underlying physics that can be drawn from the success or
failure of the approximation.
