  The effects of the onset of deconfinement on longitudinal and transverse flow
are studied. First, we analyze longitudinal pion spectra from $E_{\rm lab}= 2A$
GeV to $\sqrt{s_{\rm NN}}=200$ GeV within Landau's hydrodynamical model and the
UrQMD transport approach. From the measured data on the widths of the pion
rapidity spectra, we extract the sound velocity $c_s^2$ in the early stage of
the reactions. It is found that the sound velocity has a local minimum
(indicating a softest point in the equation of state, EoS) at $E_{\rm
beam}=30A$ GeV. This softening of the EoS is compatible with the assumption of
the formation of a mixed phase at the onset of deconfinement. Furthermore, the
energy excitation function of elliptic flow ($v_2$) from $E_{\rm beam}=90A$ MeV
to $\sqrt{s_{\rm NN}}=200$ GeV is explored within the UrQMD framework and
discussed in the context of the available data. The transverse flow should also
be sensitive to changes in the equation of state. Therefore, the
underestimation of elliptic flow by the UrQMD model calculation above $E_{\rm
lab}= 30A$ GeV might also be explained by assuming a phase transition from a
hadron gas to the quark gluon plasma around this energy. This would be
consistent with the model calculations, indicating a transition from hadronic
matter to ``string matter'' in this energy range.
