  The question of how long a particle takes to pass through a potential barrier
is still a controversial topic in quantum mechanics. Arguably, the main
theoretical problem in obtaining estimates for measurable times is the fact
that previously defined time operators, that remained within the borders of
standard quantum mechanics, present some kind of pathology. Recently, a time
operator acting on an additional Hilbert space has been shown to support both
Hermiticity and canonical relation with an energy observable. The theory is
built in a framework which treats space and time as symmetrically as possible,
in the nonrelativistic regime. In this work, we use this formalism to derive a
closed analytic expression for the traversal time of a quantum particle
impinging on a constant-potential barrier. We test our theory in the specific
experimental scenario of a realization by Rafagni et al [Appl. Phys. Lett. {\bf
58}, 774 (1991)]. The proposed approach displays a much better performance in
comparison with the B\"uttiker-Landauer and the phase-time approximations.
