Introduction: Haemorrhage is the major cause of early mortality following traumatic injury. Patients suffering from non-compressible torso haemorrhage are more likely to suffer early death. Resuscitative Endovascular Balloon Occlusion of the Aorta (REBOA) can be effective in initial resuscitation; however, establishing swift arterial access is challenging, particularly in a severe shock. This is made more difficult by anatomical variability of the femoral vessels. Methods: The femoral vessels were characterised in 81 cadaveric lower limbs, measuring specifically the distance from the inferior border of the inguinal ligament to the distal part of the origin of the profunda femoris artery (PFA), and from the distal part of the origin of the PFA to where the femoral vein lies posterior to and is completely overlapped by the femoral artery. Results: The femoral vein lay deep to the femoral artery at a mean distance of 105 mm from the inferior border of the inguinal ligament. The PFA arose from the femoral artery at a mean distance of 51.1 mm from the inguinal ligament. From the results, it is predicted that the PFA originates from the common femoral artery approximately 24 mm from the inguinal ligament, and the femoral vein is completely overlapped by the femoral artery by 67.7 mm distal from the inguinal ligament, in 95% of subjects. Conclusions: Based on the results, proposed is an ‘optimal access window’ of up to 24 mm inferior to the inguinal ligament for common femoral arterial catheterisation for pre-hospital REBOA, or more simply within one finger breadth.