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Information on Lap Belts

First, it should be understood that it is perfectly safe to use a lap belt to install harnessed child restraints.  In the US, all harnessed child restraints must pass the current standards using a lap only belt.  There is a stricter standard that allows the use of a tether. However, for any belted individual, they do not provide adequate protection. They generally prevent the individual from being ejected, but do not protect the head, neck, spine or internal organs adequately.
There are two types of injury associated with using a lap only belt:
  • Head and/or neck injury. This is caused when the individual is thrown forward and has no upper body restraint. They continue moving forward until they are stopped by something. Many times, it is the head that contacts the interior of the vehicle - dashboard, front seats, consoles, door frames, even the floor of the vehicle or the individual's knees. The injuries can be severe brain trauma from impacting something at a high rate of speed, cuts, abrasions, skull fractures, broken neck, jaw fractures, orbital fractures, etc. The neck can also be severely injured including the spinal cord being severed. The spinal cord is not able to be stretched beyond a certain point. In frontal crashes, a lap only belt will hold the lower body in place, but the heavy head will pull the upper body forward at a high rate. If the head does not contact anything to stop the rapid forward motion, the neck will eventually stop the head, but the force of this will stretch the neck bones, muscles and even the spinal cord - often beyond it's limit. Children and adults both have been paralyzed or killed in this manner - their spinal cord simply wasn't capable of stretching enough to withstand the crash force.
  • Seat Belt Syndrome. Seat Belt Syndrome, or SBS, is a phrase that was originally coined by the medical community in the late 1950s and early 1960s to describe injuries that physicians were seeing as a result of occupants wearing lap-belt-only restraints in frontal collisions. These injuries typically include: (1) severe abdominal injuries, (2) fractures of the lumbar spine, and (3) serious closed head and facial injuries. These injuries are primarily the result of the occupant's body jackknifing over the lap belt, at the waist, during the collision. Under such circumstances, the lap belt causes extreme force to be applied along the pelvis to the mid-section of the occupant. Securing the waist without securing the upper torso leads to increased head and neck velocities, which can cause serious head and neck injuries following either a head strike or inertial loading of the spine. A majority of these injuries can be prevented by the installation of an integrated three-point belt or other upper-torso restraint. (http://www.mobar.net/journal/1999/mayjun/langdon.htm)

Click on image to see the difference between a lap belt only and shoulder belt

When the lap belt does all the restraining, it, and the part of the body it is holding, take the entire force of the crash. On a child, the lap belt does not sit down on the hips, as it should, but most often rides up over the soft abdominal area. In a crash, the lap belt pulls toward the seat back and the body is pulled away from the seat back. These conflicting forces concentrate a lot of energy on two things that are very vulnerable - the abdominal organs, and the spine. The injuries that are associated with SBS include, but are not limited to:
  • liver
  • kidney
  • spleen
  • intestinal
  • stomach damage.
Some of these organs get damaged beyond repair, meaning life-long handicap or death. The other injury is paralysis - not from neck injury, but from the lap belt actually severing the lower part of the spinal cord.
Kathleen Weber's research paper "Crash Protection for Child Passengers" says:
    The question of fatality reduction effectiveness of rear-seat lap vs. lap/shoulder belts has recently been addressed in an extensive double-pair analysis by Morgan in which children of age 5 through 14 were included and evaluated separately. The conclusions for rear-outboard occupants in this age group are that lap-belted children were 38% less likely to die than unrestrained children, while lap/ shoulder-belted children were less likely by 52%. The lap/shoulder belt was found to reduce fatalities 26% over lap belts alone for children 5 through 14 in all crashes and 31% in frontal crashes, and children derived more relative benefit from the lap/shoulder belt than did the adult groups. Further analysis with supplemental cause of death data indicated that both types of belted children were somewhat more likely to receive abdominal injuries than unrestrained children, but the increase for the adult groups in lap belts was much greater. Finally, both belt systems markedly reduced fatal head injuries, but these were still twice as likely among lap-belted than lap/shoulder-belted children. This study makes it clear that shoulder belt use is very beneficial for older children.
With a lap belt, you only have two anchor points...two points of protection. On most children, those two points are going to be poorly positioned. A lap/shoulder belt provides three points of protection, include upper body protection, and a booster that must be utilized with a lap/shoulder belt properly positions those points for optimal effectiveness.

  • Many of the injuries associated with lap only belts are also associated with shield boosters.
  • A booster seat should NEVER be used with a lap-only belt.  Options for kids over 40 lbs with lap only belts
  • Children up to 40 lbs are best protected in a harnessed seat - either a convertible seat, a forward-facing only seat, or a combination seat.


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