Growing multispacecraft networks are broadening the opportunity of measuring energy spectra of energetic particles at interplanetary shocks over three decades or more in energy at the same distance (different from 1 AU) from the Sun. Energetic particles spectra at interplanetary shocks often exhibit a non power law shape, even within two energy decades. We have introduced a 1D transport equation accounting for particle acceleration and escape that allows for escape at all particle energies not only the highest energies and with no free-escape boundary. The diffusion is contributed by self-generated turbulence close to the shock and by pre-existing turbulence far upstream. The momentum spectrum is used to fit the spectra of the 16 GLE events of solar cycle 23.