This study investigated and compared the simulated operational measures of effectiveness for similar traffic volumes, left-turn percentages, and access point densities for a case study roadway with a four-lane undivided and a three-lane cross section. The objective of this study was to quantify the operational impacts of this type of conversion. Actual four- lane undivided to three-lane conversions have shown decreased crashes and crash rates, produced small reductions in average arterial travel speed (similar to the CORSIM results), and resulted in large reductions in the number of speeding vehicles. Four analysis tools were reviewed and the CORSIM model was chosen to complete a sensitivity analysis that included five simulations for each combination of four average daily traffic levels, three left-turn volumes, and six access point densities. The arterial level of service (LOS) decreased from LOS C to D when the average daily traffic was 20,000 vehicles per day (the largest volume considered). The timing of the two-phase signalized intersections within the simulated corridor was optimized and did not experience a change of more than 5.5 seconds per vehicle in average stopped delay (i.e., no overall intersection LOS change). In general, a statistically significant difference in average arterial travel speed was found when four-lane undivided roadways were compared to similar three-lane roadways. The magnitude of the difference, however, ranged only from 0.5 to 3.9 miles per hour.