The novel "travelling fluidized bed" (TFB), operated under identical conditions, was deployed to compare alternate experimental measurement techniques for the investigation of solid motion in gas-fluidized beds operating in the square-nosed slugging regime. Measurements of particle velocity obtained by radioactive particle tracking (RPT - non-invasive at the Ecole Polytechnique de Montreal), positron emission particle tracking (PEPT non-invasive at University of Birmingham), optical fibre probes (invasive at UBC) and borescopic high speed particle image velocimetry (invasive at PSRI) are compared for sand particles of mean diameter of 292 mu M. Significant differences between the time-average radial profiles of particle velocity are observed in many cases. The results provide valuable insights into the merits and challenges of advanced particle velocity measurement techniques. (C) 2015 Elsevier B.V. All rights reserved.