  The correlation-driven metal-insulator transition (MIT) of BaVS$_3$ was
studied by polarized infrared spectroscopy. In the metallic state two types of
electrons coexist at the Fermi energy: The quasi 1D metallic transport of
$A_{1g}$ electrons is superimposed on the isotropic hopping conduction of
localized $E_g$ electrons. The "bad-metal" character and the weak anisotropy
are the consequences of the large effective mass $m_{eff}\approx7m_e$ and
scattering rate $\Gamma\geq160$ meV of the quasi-particles in the $A_{1g}$
band. There is a pseudo-gap above $T_{MI}=69$ K, and in the insulating phase
the gap follows the BCS-like temperature dependence of the structural order
parameter with $\Delta_{ch}\approx42$ meV in the ground state. The MIT is
described in terms of a weakly coupled two-band model.
