In fact, Residual Networks can be viewed as a special case of Highway Networks where both the transform and carry gates are substituted by the identity mapping function: thereby forming a hard-wired shortcut connection x. Arguably, Equation (3) can be considered as a form of residuality with o k working as the residual function and u k the shortcut connection.
as discussed in (Srivastava et al., 2015b), in contrast to the hard-wired skip connection in Residual Networks, one of the advantages of Highway Networks is the adaptive gating mechanism, capable of learning to dynamically control the information flow based on the current input.