Yes! For everyday convenience, city-dwellers traveling in cabs, or vacationing families, the base is not required to achieve a safe and secure install. The lap belt routes through the blue guides that are located near the carrying handle of carrier when rear facing. Please reference your MESA manual and your vehicle manual for seat belt guidance.
For MESA models with European routing method, reference blue guide on back of carrier – The shoulder belt routes behind the carrier in the blue guide once pulled out. If the shoulder belt is not long enough to route behind, then just route the lap belt and let the shoulder belt retract back into the vehicle seat.
Please make sure that the red line on the side of the carrier is parallel to your vehicle floor rather than the ground outside the vehicle. Ensure the back angle of the carrier stays in the correct position so the baby’s head is not flopping forward and closing their airway.