  We demonstrate two techniques for studying the features of three-level
systems driven by two lasers (called control and probe), when the transitions
are Doppler broadened as in room-temperature vapor. For $\Lambda$-type systems,
the probe laser is split to produce a counter-propagating pump beam that
saturates the transition for the zero-velocity atoms. Probe transmission then
shows Doppler-free peaks, which can even have sub-natural linewidth. For V-type
systems, the transmission of the control beam is detected as the probe laser is
scanned. The signal shows Doppler-free peaks when the probe laser is resonant
with transitions for the zero-velocity group. Both techniques greatly simplify
the study of three-level systems since theoretical predictions can be directly
compared without complications from Doppler broadening and the presence of
multiple hyperfine levels in the spectrum.
