  We study the motion of particles in the background of a four-dimensional
linear dilaton black hole. We solve analytically the equations of motion of the
test particles and we describe their motion. We show that the dilaton black
hole acts as a particle accelerator by analyzing the energy in the center of
mass (CM) frame of two colliding particles in the vicinity of its horizon. In
particular we find that there is a critical value of the angular momentum,
which depends on the string coupling, and a particle with this critical angular
momentum can reach the inner horizon with an arbitrarily high CM energy. This
is known as the Ba\~nados, Silk and West (BSW) process. We also show that the
motion and collisions of particles have a similar behavior to the
three-dimensional BTZ black hole. In fact, the photons can plunge into the
horizon or escape to infinity, and they can not be deflected, while for massive
particles there are no confined orbits of first kind, like planetary or
circular orbits.
