LATCH Weight Limits: The Whole Story

What is LATCH?

LATCH stands for Lower Anchors and Tethers for CHildren. The lower anchors are a way of connecting the car seat to the vehicle that does not use the vehicle’s seat belts. The tether is an additional strap that secures the top of the car seat to the frame of the vehicle.

Rigid LATCH: Clek Foonf with rigid lower anchors (circled in blue)

IS LATCH SAFER THAN THE SEAT BELT?

NO!** Seat belts have always been a very safe and effective way to secure a car seat… the problem is that getting a secure installation with a seat belt is often confusing and challenging. LATCH was invented in an attempt to decrease the misuse rate for car seats by giving parents an easier way to secure the child’s car seat to the vehicle. Unfortunately, LATCH did not reduce the misuse rate for car seats; the misuse rate continues to be approximately 90%.

WELL… MAYBE THERE IS ONE TYPE OF LATCH THAT IS SAFER.

**There is one subset of LATCH, found on a few car seats in the US, but widely across Europe, that just may be safer than not only other types of LATCH, but also the seat belt. “Rigid LATCH” is when the lower anchor connectors are rigidly connected to the steel frame of the child’s car seat; this is in contrast to “flexible LATCH” where the lower anchor connectors are sewn on to a flexible strap that you must tighten. Rigid LATCH, by directly securing the steel frame of the child’s car seat to the steel frame of the car, virtually eliminates the side-to-side motion of the car seat in a side-impact.  As such, rigid LATCH can better contain the child’s body within the shell of the seat and decreases the chance of the child’s body hitting a hard structure in the vehicle, since the child’s seat can not move as much laterally as it can with flexible LATCH or the seat belt.

Vehicle Seat with close-up of Lower Anchor and symbol on plastic dot

WHAT ARE THE LOWER ANCHORS?

Lower anchors are a pair of metal bars in the vehicle’s seat crack.  The anchors, while typically hidden from view, are often marked off by small tag or plastic dot on the vehicle’s seat back.

WHAT ARE THE LOWER ANCHOR CONNECTORS?

Lower anchor connectors can be found on all rear-facing seats, forward-facing seats, and some boosters. They usually are typically a hook or “stapler” at the end of a strap.  The lower anchor connectors secure to the lower anchors in the vehicle’s seat crack.

DO I USE THE SEAT BELT AND THE LOWER ANCHORS AT THE SAME TIME?

NO (usually). The lower anchors are typically used INSTEAD OF the vehicle’s seat belt.

There are a few exceptions. The most common exception is with booster seats that offer LATCH, where the lower anchors will secure the booster to the vehicle, and then the vehicle’s seat belt goes across the child’s body to secure the child.

For 5-point harness car seats, there are only 2 seats that currently allow you to use the lower anchors AND seat belt.  1. The Clek Foonf (a convertible seat) when used FORWARD-facing uses the rigid lower anchor connectors AND the vehicle’s seat belt (and the tether too) – which effectively negates the entire issue discussed below of the lower anchors having weight limits. 2. The Nuna Pipa infant seat also allows the use of the rigid lower anchor connectors AND the vehicle’s seat belt.

CAN I USE THE SEAT BELT AND THE LOWER ANCHORS AT THE SAME TIME?

Unless you have a Nuna Pipa base or a forward-facing Clek Foonf, NO you can not use both.  Trust that the car seat manufacturer knows their seat best. Unless they tell you to use both, they don’t want you to use both.

Identical seats with identical dummies except farther seat is NOT using the tether, closer seat is. Tether decreases forward head movement by 6 inches!!!

WHAT IS A TETHER?

A tether is the most important part of EVERY forward facing car seat. Tethers (also called top tethers) are a way of connecting the top of the child’s car seat to the vehicle. It’s a two-part system: there needs to be a tether anchor in the vehicle and a tether strap on the child’s car seat. Tethers are never used by themselves; they are always used in addition to the lower anchors or the vehicle’s seat belt. Tether straps can be found on the top of every forward-facing car seat—and some booster seats too. While all convertible seats have tether straps (because convertibles can be used forward facing), onlya few allow the tether to be used when the seat is rear-facing.

WHAT IS THE PURPOSE OF A TETHER?

Tethers decrease how far the child’s head moves forward in a crash by 6-8 inches. Tethers are tremendously important in keeping your child’s brain and spinal cord safer.  Tethers spread the stress of the crash onto a larger area of the car seat, rather than concentrating the stress along the belt path. With some car seats, tethers allow the sides of the car seat to cocoon the child, rather than with untethered seats where the sides flail out.

WHICH CHILD SEATS HAVE LOWER ANCHORS? WHICH HAVE TETHERS?  

CAR SEAT TYPE LOWER ANCHORS? TOP TETHER?
REAR-facing-only CARRIER NO

(exception: when carrier is sold withOUT base)

NO
REAR-facing-only BASE YES NO
REAR-facing CONVERTIBLE YES YES

(a few allow the use of the tether when seat is rear-facing)

FORWARD-facing with 5-Point Harness YES YES
BOOSTER with a HIGH back MAYBE

(some allow use of lower anchors in booster mode)

MAYBE

(some allow use of tether in booster mode)

BOOSTER with NO back MAYBE

(some allow use of lower anchors in booster mode)

NO

LOWER ANCHOR WEIGHT LIMITS

WHY DO LOWER ANCHORS HAVE WEIGHT LIMITS?

There is concern that the lower anchors in the vehicle may not be strong enough to hold heavier kids in heavier seats in some crashes. In a crash, it is the combined weight of the child + car seat that pulls on and stresses the lower anchors. When LATCH was first conceived, there was no such thing as a 5-point harness for a child over 40 pounds and most car seats weighed well under 20 pounds. Today, car seats typically accommodate heavier kids with some 5 point harnesses fitting kids up to 90 pounds. In addition, the car seats are heavier too; many weigh 20-25 pounds, and one weighs 36 pounds!

HAVE THERE BEEN ANY CRASHES WHERE THE LOWER ANCHORS FAILED OR BROKEN?

Three in the crash test lab, but none in real world crashes.

If a lower anchor were to break in a crash, it is most likely to occur with a heavier child in a heavier car seat in a higher speed crash as this scenario puts the most stress on the lower anchors. If the lower anchors do have a maximum weight that they can withstand, we will see this problem manifested in real world crashes only when there are more children using heavier car seats to higher weights. HOWEVER, right now it is purely conjecture that the lower anchors have a maximum weight that they can withstand… as they have never broken in a real world crash that we are aware of.

Here are details on the failures in the crash test lab:

  • Failure #1:
    • Testing done by Transport Canada using a 2007 Nissan Versa
    • MISUSE testing – as car seat was installed with LATCH in center seat, but center was NOT a designated LATCH position (only the 2 side seats were designated LATCH positions)
    • 10y/o dummy (78 pounds) + Britax Regent (25 pounds) = 103 pounds total
    • Notably, the tether strap slipped into the vertical split between the seat backs, causing an abrupt shift of the forces
    • Importantly: child dummy remained in his car seat and the injury measures were not serious
  • Failure #2:
    • Testing done by Transport Canada using a 2010 Kia Forte
    • Car seat installed on the side using LATCH (lower anchors + top tether)
    • MISUSE: Apex 65 harness weight limit is 65 pounds, but dummy weighed 78 pounds
    • 10y/o dummy (78 pounds) + Cosco Apex 65 (13 pounds) = 91 pounds total
    • 35 mph frontal crash test, peak vehicle acceleration was 46 G.
    • The total maximum anchorage loads measured in this test was 20,395 N.
    • During the test, the inboard anchor, which was held in place by two bolts, pulled through the sheet metal resulting in a failure at the attachment point.
  • Failure #3:
    • Testing done by NHTSA using a Kia Forte buck and a front loaded sled pulse at NHTSA’s Vehicle Research and Test Center
    • 6y/o dummy (66lbs) + Cosco Apex 65 (13 pounds) = 79lbs combined
    • Car seat installed on the side
      • First test: installed with LATCH (lower anchors + top tether)
        • Some deformation of the sheet metal with some forward pull of the lower anchors but not a complete failure of the anchorw. The total anchor loads (lower anchors+tether) was measured to be 17,330 N and the total load on the lower anchors (inboard+outboard) was 11,666 N
      • Second test: installed with just the lower anchors (no top tether)
        • Complete failure of the lower anchor hardware. The entire bolt and nut assembly pulled through the sheet metal. The total measured force on the lower anchors in this test was 14,922 N, which is 30 percent higher than the total lower anchor load in the earlier test with the tether attached.
        • Note: this seat did not require the use of the tether

WHAT ARE THE LOWER ANCHOR WEIGHT LIMITS?

For all car seats made on or after February 27, 2014 the government has imposed maximum weight limits on the lower anchors. The limit depends on when your car seat was made.

For car seats made AFTER February 28, 2014:

Your car seat will state – both on a sticker on the car seat as well as in the instruction manual – the maximum child’s weight for using the lower anchors. If your seat goes rear-facing and forward-facing, be aware that the child weight limits in many cases are different for rear-facing and forward-facing.

For rear-facing car seats, the government allows a maximum combined weight of child + car seat of 65 pounds to use the lower anchors. For forward-facing car seats, the government allows a maximum combined weight of child + car seat of 69 pounds to use the lower anchors. The higher limit for forward-facing is given with the assumption that the forward-facing seat will use a tether in addition… which decreases the stress on the lower anchors in a crash.

However, car seat manufacturers do not have to allow up to this maximum. For example, Britax has chosen to make 40 pounds the maximum child’s weight for using the lower anchors for ALL of their seats (except the infant seats because these don’t go to 40 pounds anyway). So, while the Britax Advocate G4  weighs about 19 pounds, and the government would allow the lower anchors to be used up until a child’s weight of 50 pounds (69-19=50), Britax is only allowing up to a child’s weight of 40 pounds.

Conclusion: You must follow the instructions given by the car seat manufacturer.

For car seats made BEFORE February 28, 2014:

First, follow the instruction manual to your child’s car seat. Most car seats will tell you the maximum child’s weight for using the lower anchors.

If the car seat’s lower anchor weight maximum is higher than you were expecting (or are higher than on the same seat made after Feb 27, 2014), please understand that the new limits are NOT retroactive. However, if you would rather take the more conservative route and follow the new limits even on an older seat, you can do so at any time – as seat belts are a very safe and very effective way of securing a car seat to the vehicle.

Also, check to see what your vehicle manufacturer has to say. Some will give a weight limit, others won’t.  This table is the most up to date information from the vehicle manufacturers regarding their current lower anchor weight limits. The information in the table is taken from the LATCH Manual by SafeRideNews and in some instances the information in the LATCH manual is the ONLY published, vehicle manufacturer-approved source of the information.

If the car seat does NOT state a maximum, then do the following:

  1. Call the car seat manufacturer and ask them what they advise. If the manufacturer is still making this seat after Feb 27, 2014 you can simply find out what the maximum weight limit being used for the newer seats is and follow this.
  2. OR: Check this chart to see how much the car seat weighs – and do some math. For rear-facing, 65 – car seat’s weight is the maximum child’s weight for using the lower anchors. And for forward-facing, it is the same equation but with 69 pounds.

Second, check the owner’s manual to your vehicle to see if they state a maximum child’s weight for using the lower anchors.

DO THE LOWER ANCHOR WEIGHT LIMITS APPLY TO BOOSTERS ALSO?

Short answer: NO.

First, lets define “booster”; a booster is a seat the child sits on and the child uses the vehicle’s seat belt across them. If the child is using a 5-point harness that comes from their seat, then they are NOT using a booster, and are instead using a car seat. This confuses many parents as there are lots of seats that start out as 5 point harness car seats and can then turn into boosters.

Some booster seats now come with lower anchors. There is NO WEIGHT LIMIT to the lower anchors for booster seats because the booster is not the restraint and does not take the force of a crash. This is in contrast kids sitting in a car seat with a 5 point harness where the car seat DOES take the force of the crash and pulls on the lower anchors.

MY CHILD EXCEEDS THE WEIGHT LIMIT OF THE LOWER ANCHORS… NOW WHAT?

DO I HAVE TO BUY A NEW SEAT?

NO! So long as the child is still within the weight and height limits for the 5-point harness, you can continue to use the car seat but must install it using the vehicle’s seat belt instead of the lower anchors. You should continue to use the tether on every forward facing car seat as it significantly reduces the chance of brain and spinal cord injuries.

DOES THIS MEAN MY CHILD HAS TO GO INTO A BOOSTER NOW?

NO! Your child can continue to use a seat with a 5 point harness so long as they are within the weight and height limits for the 5 point harness on that seat… just make sure you install the car seat using the vehicle’s seat belt (and the tether), not the lower anchors.

DO TETHER ANCHORS HAVE WEIGHT LIMITS TOO?

Some vehicle manufacturers are stating weight limits on their tether anchors.  As a pediatrician, this deeply troubles me as I try to practice evidence-based medicine.  Limiting the use of tethers exposes the child to proven risks in the hopes of preventing what remains only a theoretical risk (i.e., the tether breaking). Even if the worst case scenario should happen and the tether should fail in a crash, it is likely to break towards the end of the crash—after it has helped manage a lot of the energy of the crash—and would likely still offer significant benefit to the child. A potential risk to the tether breaking in a crash is that the metal hook at the end of the tether strap could fly and hit the child; however, without the tether, the child stands a significantly increased risk of hitting his head on hard structures like the window, door frame, or the back of the front seat.

Note: Recaro is the only manufacturer to specifically state that they want you to stop using the tether after a certain weight; on their ProSport, they do not allow the use of the tether when the child weighs more than 52 pounds. In discussions with the company, there was no scientific reason given for this limit. Ironically, most car seat manufacturers REQUIRE the use of the tether as children get heavier.

WHAT ARE THE CHILD CAR SEAT MANUFACTURERS DOING IN LIGHT OF THE LOWER ANCHOR WEIGHT LIMITS?

A few child car seat manufacturers are getting more innovative with the design of their seats to make it easier for parents to install for heavier kids.

For example:

When using the Clek Foonf forward-facing, you can use the lower anchors to the full maximum of the seat (a child’s weight of 65 pounds) despite the fact that the car seat itself weighs 32 pounds. How is this possible? Clek did extensive testing to show that on their seat using the rigid lower anchors + vehicle’s seat belt + tether is very safe when the seat is used forward facing. The seat belt is the “back-up plan” so that should the lower anchors not be strong enough, the seat belt will hold. The Foonf’s crumple zone technology (REACT system) requires the use of the lower anchors so installing the seat with just the seat belt + tether forward facing would mean missing out on this great feature of this seat.

Britax’s Frontier 90 & Pinnacle 90 feature their “click tight” technology which makes for one of the easiest seat belt installations ever… meaning that you won’t even miss using LATCH as the seat belt installation is as easy as can be. Remember to still use the tether at all times!

WHAT ABOUT THE SUNSHINE KIDS / DIONO CAR SEATS WITH SUPERLATCH?

It depends on whom you ask.  But first, an explanation of superLATCH.  superLATCH is a stronger lower anchor connector – as it has 4 metal “teeth” instead of the typical single metal “tooth”.  This picture here shows a regular lower anchor connector on the left and a superLATCH connector on the right. superLATCH has nothing to do with the lower anchor in the vehicle – it is simply a stronger means of connecting the car seat to the lower anchor in the vehicle.

If you believe that the lower anchors in the vehicle are strong enough to hold any weight of child + car seat, then you would side with Sunshine Kids / Diono on this issue and feel comfortable using their seats with the lower anchors + tether to the maximum weight allowed for the 5 point harness (65 or 80 pounds depending on which particular seat you have).  If, however, you believe that the lower anchors in the vehicle may not be strong enough to hold any weight of child + car seat, then you would choose to ignore the issue of superLATCH and would stick to the 65 or 69 pound combined weight.

All Diono seats made after Feb 28, 2014, even those with superLATCH, must comply with the new government regulations. As such, the lower anchor weight limit is a child’s weight of 35 pounds for rear-facing and 40 pounds for forward-facing on the Diono Radian seats.

Note: superLATCH – namely Sunshine Kids/Diono’s permission to use the lower anchors beyond the vehicle’s stated lower anchor weight limit – ONLY applies to vehicles model year 2006 and newer.  For vehicles 2005 and older, you must consult the vehicle manual for the lower anchor weight limit.

DO SEAT BELTS HAVE WEIGHT LIMITS?

NO! Seat belts are tested to withstand at least 6,000 pounds of force – and can hold even very large adults.

CAN I USE THE LOWER ANCHORS + VEHICLE’S SEAT BELT?

Unless the child’s car seat specifically allows this (currently, the Nuna Pipa base and the Clek Foonf when used forward-facing are the only seats to allow this) you do NOT want to do this as even though it may seem like a good idea, it turns your child into a guinea pig. If it turns out to not work well in a real crash your child will suffer the consequences. Trust the manufacturer that they know their seat better than you do – if they don’t tell you to do something, don’t do it. Children don’t deserve to be guinea pigs.

 

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