  It has been proposed that the Siverse transverse single spin asymmetry in
Drell-Yan production in transversely polarized p+p collisions would have an
opposite sign compared to what has been observed in the polarized
Semi-Inclusive Deep Inelastic Scattering (SIDIS) experiments. Experimental
confirmation or disproval of this prediction would provide a new fundamental
test of QCD and shed new light on our theoretical understanding of the
transverse spin physics phenomena. We discuss the prospects and physics
sensitivities of polarized fixed target Drell-Yan experiments that could
utilize the existing proton and other hadron beams at Fermilab, and polarized
proton beams at RHIC with a polarized solid proton and/or neutron target
option. We show that if realized, the new experiments would provide critical
measurements of not only the sign change (or not) of Sivers functions, but also
the information of quark and antiquark's Sivers distributions over a wide
kinematic range.
