The standard THOR-50M dummy is equipped with sensors to measure the abdomen deflection and assess the risk of abdominal injuries. Since 2016, the "ABdominal Injury and SUbmarining Prediction" (ABISUP) consortium has developed a pressure-measuring abdomen for the THOR-50M to predict abdominal injuries and submarining as a potential alternative to the current THOR-50M abdomen design. A new lower abdomen including Abdominal Pressure Twin Sensor (APTS) was designed and four identical prototypes were built and shipped to consortium member test houses. Numerous abdominal belt loadings replicating tests from the literature were carried-out to check the prototype biofidelity, sensitivity and define a pressure-based AIS3+ injury risk functions (IRFs). Two compression-based IRFs were defined using porcine test results from the literature[7]. Compressions were defined as the ratios between the abdomen deflection and the full abdominal depth, or between the abdomen deflection and the abdominal depth in front of the spine. The abdominal depth in front of the spine was used in an attempt to minimize possible differences between species. It was estimated using simple assumptions and led to compressions exceeding 100% in a few cases. Then transfer functions between THOR abdominal compressions and pressures were applied to obtain the pressure-based IRFs. Twenty-five sled tests were performed to assess the new abdomen under various restraint conditions and to evaluate the relevance of the IRFs.The THOR-50M new abdomen showed similar or better biofidelity than the standard abdomen without modifying the dummy kinematics. The abdomen was sensitive to loading height and no damage to the APTS was encountered during tests. Relationships between THOR-50M mean APTS pressure and abdominal compressions were modelled using a 3rd degree polynomial with 0.98 R². The IRF with a log-logistic distribution obtained the lowest Akaike Information Criterion. For the compression based on the full abdomen depth, the AIS3+ injury risks of 25%, 50% and 75% corresponded to APTS pressures of 133, 201 and 304 kPa, respectively. For the compression based on the abdomen in front the spine, the AIS3+ injury risks of 25%, 50% and 75% corresponded to APTS pressures of 108, 197 and 361 kPa, respectively.The new abdomen discriminated between the restraint conditions: lower pressures (between 90 and 190 kPa) were obtained when the lap belt remained below or on the ASIS and higher pressures (170 to 450 kPa) were obtained when the lap belt loaded the abdomen. Using the IRF, a risk up to 50% could be obtained without submarining, i.e. with the lap belt still engaging the ASIS. This is not consistent with a risk expected to be low for a proper restraint. Possible adjustments are discussed in the paper to decrease APTS sensitivity when the lap belt is positioned below or on the ASIS.