A simulation-based study was conducted to investigate the effects of exempting low-emitting vehicles (specifically hybrids and E85 alternative fuel vehicles (AFVs)) from occupancy requirements in high occupancy vehicle (HOV) lane and express toll lane (ETL). Numerical experiments involved various levels of hybrid penetration rates and results were studied. Emission estimates resulting from various AFV penetration levels were compared to those of hybrids at the same penetration levels. It was concluded that exemptions would not significantly degrade the managed lane use at low penetration rates. Performance deterioration was noted at penetration rates of 11.42% and at 26.56% and higher for the HOV lane facility and at penetration levels of 21.89% and higher for the ETL facility. Network-wide emissions and fuel consumption slightly increase while emissions and fuel consumption per vehicle miles traveled generally decrease. Moreover, hybrid vehicle technologies were found to result in greater emissions savings as compared with E85 AFVs.