Finite element (FE) model simulations of frontal sled tests using a 3-year-old Hybrid III dummy FE model and child human FE model seated in a 5-point harness ISOFIX CRS were conducted. A countermeasure of setting a force limiter in the top tether was proposed, which showed an effectiveness on reducing head and chest acceleration and the upper neck loads, just the head excursion increasing but still below the Injury Assessment Reference Value (IARV).