corresponding channel threshold at which the collision effectively behaves as in free-space. This energy is found to be independent of the number of open channels for $s$- and $p$-wave interactions. Furthermore, we investigate the unitarity bounds for quasi-1D collisions. This quantitatively explains the transmission at a CIR in higher transversal modes and explains the confinement induced unitarity bound, from which we also derive the unitarity bounds for inelastic collisions in the waveguide. These bounds may be useful when investigating the possibilities and limitations of populating higher transversal modes by means of a CIR, as interest in coherent excitations in waveguides increases [@buecker2011; @buecker2012; @vanfrank2014]. Next, we investigate the intriguing possibility of a blockade in the first excited transversal mode, found from the quasi 1D unitarity bound in the [$d$-SPWA]{}, with an adequate interatomic potential and the coupling of partial waves taken into account, showing that an almost totally blockaded transmission channel may exist even if there are other possible scattering channels available. In addition we discuss the scattering of distinguishable particles in waveguides and show the qualitative difference of partial wave coupling for distinguishable particles by introducing resonance and transparency coefficients [@hess2014]. We discuss the occurring threshold singularities for collisions 