In Australia and the United States the longwall gateroad design methodologies ALTS (Analysis of Longwall Tailgate Serviceability) and ALPS (Analysis of Longwall Pillar Stability) were developed to assist in the design of chain pillar systems to satisfy gateroad serviceability requirements. Important to the application of both methods is a reasonably accurate determination of the vertical load carried by the chain pillars at the various stages of the longwall extraction cycle. To calculate the load, use is made of Tributary Area concepts and the Abutment Angle Model. While Tributary Area Theory and the Abutment Angle Model generally assist in providing a reasonable approximation to a complex issue; chain pillar monitoring studies conducted in Australia over approximately the last 30 years strongly indicate that without the application of prudent engineering judgment significant errors in the calculation of the abutment loads carried by the chain pillar system can be made. This paper explores the appropriate use of the Abutment Angle Model for longwall tailgate design and details a number of case studies to highlight the issue.