</p>In our tests of the Britax Frontier toddler booster seat, installed with a lap belt and without the top tether, and tested with a harnessed 52-lb., 6-year-old hybrid III dummy, the dummy's head exceeded the limits for head excursion that would be allowed by the standard test. That means the head moved forward more than the federal standard for child seats allows. Additional forward head movement in a real crash can potentially expose a child's head to injury. When we tested the same seat with the top tether installed, and with a 3-point safety belt, the head excursions were within the limits. Based on those results and recommendations from the Britax manual, we would not recommend use of the Britax Frontier for older vehicles that have only a lap belt for installation and lack a top-tether anchor.