This paper studies the effect of different longitudinal load conditions, roundabout cross-sectional geometry, and different semi-truck pneumatic suspension systems on roll stability in roundabouts, which have become more and more popular in urban settings. Roundabouts are commonly designed in their size and form to accommodate articulated heavy vehicles (AHVs) by evaluating such affects as off-tracking. However, the effect of the roadway geometry in roundabouts on the roll dynamics of semi-tractors and trailers are equally important, along with their entry and exit configuration. , Because the effect of the roundabout on the dynamics of trucks is further removed from the immediate issues considered by roadway planner, at times they are not given as much consideration as other roadway design factors. In this study, the cross-sectional geometry of circulatory roadway, a key roundabout segment, is studied to evaluate its effect on roll stability of a WB-67 semi-truck with three longitudinal load conditions, when the truck is equipped with conventional OE suspensions and a balanced pneumatic system. TruckSim is used to develop various configurations of roundabout models, as well as a detailed model of the dynamics of the semi-tractor and trailer. The pneumatic dynamics of the suspensions are modeled in AMESim, a commercial software, and merged with TruckSim model of the vehicle, using Simulink. Simulation results indicate thin the roundabout cross-sectional geometry and truck pneumatic suspension system significantly influence the roll dynamics of the truck in roundabouts, whereas the longitudinal load conditions have relatively less effect. Both the roundabout geometry and suspension dynamics can be designed to reduce the likelihood of rollovers at speeds that trucks commonly negotiate roundabouts.