  In the case of tunneling of relativistic particles, differently from the
nonrelativistic case, a limit of "transparent" barrier can also lead to an
apparent "superluminal" behavior when considering the phase time. In this
limit, the restricting condition of "opaque" barrier of the nonrelativistic
case is avoided, nevertheless, the very thin width of a single barrier to
obtain this "transparent" limit can result in a problem itself, for probing the
effect. A combination of two successive transparent barriers can show an
apparent "superluminal" behavior along a macroscopic arbitrary distance "L".
Two solutions for energy E above and below the potential square barrier V are
found, for both solutions there the apparent superluminal behavior is possible
above a threshold of free travelling group velocity (energy) and dependent on
the ratio barriers length - free path as function of the ratio group velocity -
speed of light.
