Geogrids have been widely used to reinforce paved and unpaved roads constructed on soft subgrade. To quantify the effectiveness of geogrids in low-volume flexible pavements when constructed on weak subgrade, full scale pavement test sections were constructed at University of Illinois. The pavement sections were tested using the full-scale Accelerated Testing Loading ASsembly (ATLAS). The pavement sections were instrumented, during construction, to monitor in-situ pavement response to various vehicular and environmental loading conditions. The testing was conducted using a dual-tire assembly at 44-kN load, 8 km/h speed, and 690-kPa tire inflation pressure. Post-failure forensic evaluation of the pavement sections was conducted. The evaluation included transverse profile measurements. The study found that reinforced pavement sections experienced less rutting than the unreinforced sections. Observations of the pavement cross section profile, through trenches dug after the testing was complete, confirmed that pavement failure was mainly due to subgrade shear. Copyright ASCE 2008.