decrease of $v_2(|\eta|>1)$ observed by PHOBOS in Fig.(\[line1figb\]). This discrepancy is due, in my opinion, to the onset of [*hadronic*]{} dissipation effects as the comoving density decreases with increasing $y$. From the right panel of Fig.(\[line1fig\]), we see that as a decrease of the local transverse density from midrapidity RHIC conditions leads to an increasing deviation from the perfect fluid limit. The initial density was also observed to decrease at RHIC as $|y|$ increases [@Bearden:2001qq]. Therefore, from SPS data alone, we should have expect deviations from the perfect fluid limit away from the midrapidity region. It would be interesting to superpose the PHOBOS data on top of the NA49 systematics.

To elaborate on this point, Fig.\[spsv2\] shows CERES data [@Agakichiev:2003gg] on $v_2(p_T)$ at SPS energy $\sqrt{s}=17$ AGeV. In agreement with the right panel of Fig.(\[line1fig\]), the CERES data falls well below hydrodynamic predictions. At even lower energies, AGS and BEVALAC, the $v_2$ even becomes [*negative*]{} and this “squeeze out” of plane [@Stocker:ci] is now well understood in terms of non-equilibrium BUU nuclear transport theory [@Stoicea:2004kp; @Danielewicz:2002pu].

![Evidence for dissipative collective flow below RHIC energies. Left: Non equilibrium BUU nuclear transport theory [[@Danielewicz:2002pu; @Stoicea:2004kp]]{} can explain the observed elliptic squeeze-out (negative 