  We investigate theoretically the slow group velocity of a pulse probe laser
propagating through a cold sample and interacting with atoms in a three-level
$\Lambda$ configuration having losses towards external states. The EIT
phenomenon produces very small group velocities for the probe pulse in presence
of a strong coupling field even in presence of the population losses, as in an
open three-level system. The group velocity and the transmission of the pulses
are examined numerically as functions of several parameters, the adiabatic
transfer, the loss rate, the modification of the atomic velocity produced
within the cold sample. The conditions for a more efficient pulse transmission
through the cold atomic sample are specified.
