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Using the Car Seat Harness Correctly

using the car seat harness correctly

Car Seats Series #4 : Harnessing

Estimated reading time: 7 minutes

Learning to use the Car Seat Harness correctly is important because four of the most common car seat mistakes parents make involve the incorrect use of the harness. More about those later…

After selecting the right car seat for your child’s car seat stage (selection) and installing it (direction, location and installation) — and preferably having that installation checked by a certified Child Passenger safety Technician, there is harnessing.

car seat harness

From birth to booster age you are likely using a 5-point harness car seat. This means the car seat harness system contacts your child in five points: both shoulders, both hips and the crotch. These are the strongest points of the body. A 5-point harness spreads the crash force evenly over the child.

First thing first, which direction is your child facing?

car seat harness

Deciding which slot the harness goes through the car seat depends on your child’s height and which direction your child is facing in the car.

If your child is in a rear-facing car seat, the harness strap should be at or below your child’s shoulders. Putting shoulder harnesses too high for rear-facing children has a similar effect as not fully tightening the safety harness itself.  Most car collisions happen when the car is moving forward, causing a rear-facing child’s back to be pressed against the seat back of the child restraint seat.  This means that a main goal of a rear-facing car seat harness is to keep the child’s body from sliding upwards along the child restraint’s seat back. Every tiny increment of increased distance the child moves exponentially amplifies the forces on the child’s body. The more a child’s body accelerates, the more the child’s head and chest are subjected to increased g-forces both at the beginning of the collision and during deceleration after the collision.

If your child is in a forward-facing car seat, the harness strap should be at or above your child’s shoulders. While forward-facing the crash forces will cause the child’s body to be thrown forward. The harness straps should be positioned at or above the child’s shoulders when forward facing to most effectively decrease the amount of distance the child will travel when propelled forward and to limit the forces on the child’s spine and shoulders.

Make sure the harness straps are both going through the car seat — shell and cover — at the same level and neither strap has any twists in it. When they are twisted the crash force is placed on a smaller area of the body which can cause increased injury.

Once your child is in the car seat.

Pull the harness straps over your child and buckle the harness and close the chest clip.

harness strap pinch test

Pull the harness straps to a snug tightness. This means if you try to pinch the harness horizontally you cannot pinch the material together. This is the “pinch test.”

Move the chest clip to armpit level. (We recommend tightening the straps then moving the clip up to position. If it starts high, you could tighten the straps and pull the clip right into the child’s throat.)

That seems simple enough, right?

Except that as mentioned, harnessing mistakes account for four out of ten of our most common car seat mistakes.

Those mistakes include:

1. Not having the harness straps snug enough.

A large number of parents still leave the harness too loose. At checkups we often hear them say something like, “it seems too tight and uncomfortable.”

A “snug” harness equals “a snug strap should not allow any slack. It lies in a relatively straight line without sagging. It does not press on the child’s flesh or push the child’s body into an unnatural position.” You want the straps to be “as snug as a hug.”

Why is this so important? During a crash the harness straps are holding the child in the car seat. If those straps are too loose, the child will not be properly secured and could even come out of the straps becoming an unrestrained child.

The child should not wear bulky clothing like a puffy winter coat in the car seat harness straps. During a crash the bulky clothing would compress then the straps would be too loose.

Crash testing shows with 3 inches of harness slack, the child’s shoulder can slip out of the harness allowing the child’s head to extend past the car seat and strike the vehicle door in a side-impact crash.

2. The chest clip is not at armpit level.

most common car seat mistakes

In many car seats the chest clip is meant to break during a crash, so how can the position be so important? Well, too low and the harness straps may not be positioned correctly on your child’s shoulders, especially if the straps are also too loose. In this case, the clip prevents the straps from separating, ensuring your child is not ejected during a violent crash. Too high and prior to breaking, it could compress on your child’s throat.

3. Harness straps are not properly positioned for the child.

For rear-facing child safety seats, if you are looking at the child sitting in the seat the straps should be going through the safety seat at the slot at or below the child’s shoulder. In other words, you should not be able to see the strap coming out of the seat above the shoulder, it should be hidden beneath the child’s shoulders.

When rear facing in a forward crash ­— the most common type of crash — the first motion is going to be the top of the child seat rotating down toward vehicle’s floor. If there is enough crash energy, the child’s body is going to try to slide toward the top of the child safety seat. You want the harness straps to be cradling, or at least very close to the child’s shoulder, so that they do not slide “up” into and stop suddenly or even go through the neck opening when they finally hit the misplaced straps.

For forward-facing car seats, the harness straps should go through the safety seat at or above the child’s shoulder. Think about how our seat belt is positioned on us. It anchors above our shoulder so that we lean into it in a forward impact.

Download our report: Common Car Seat Mistakes and How to Fix Them

4. Harness straps are not routed correctly through the car seat.

Why is this so important? The car seat manufacturer crash tested your car seat and meant for the straps to be used in a certain configuration. If you routed the straps incorrectly, it could interfere with the performance of the car seat during a crash. If the car seat harness straps are twisted, they may not distribute the weight correctly and cause injury.

Also remember, to not have anything thicker than sweatshirt material between your child and the car seat harness straps. This includes thick winter coats, blankets and those nice fuzzy, plush car seat covers that have a back section between the baby and car seat.

A note about cleaning car seat harness straps

When the straps need to be cleaned, wipe them with a moist cloth. You can use a baby wipe or a washcloth with a little drop of soap. Do not submerge or wash in the washing machine, this ruins the integrity of the strap. If such a thorough cleaning is necessary, you should replace the straps. Call the manufacturer of the child restraint to get new straps.

Get a visual of car seat safety rules.

5/5 of Car Seat Series; previous posts: #1 Selection#2 Direction#3 Location#4 Installation

We want to know, were you nervous to “over tighten” the car seat harness straps when you first started putting your child in a car seat? Share your comments below.

By Amie Durocher, Creative Director at Safe Ride 4 Kids and certified CPS Tech since 2004

Copyright 2022 Safe Ride 4 Kids. All rights reserved. You may not publish, broadcast, rewrite or redistribute this material without permission. You are welcome to link to Safe Ride 4 Kids or share on social media.

We originally published this post in January 2017. We updated the article for accuracy and comprehensiveness.

© amie durocher
© amie durocher
© amie durocher


  1. I have seen people tighten the straps so much that it was very hard to fasten and was pressing down a lot on the child’s shoulders. What harm can this be to the child’s posture or spine.

    1. Hi Debbie, We could see that over tightening harness straps for a rear-facing child or a forward-facing child where the harness straps are incorrectly placed behind the shoulders instead of above the shoulders may impact the spine. Though we have not seen any studies or reports to this affect. More often than not, the harness straps are not any where near tight enough. Quite often parents feel that properly tightened harness straps are over tight. So it could be a matter of perspective. You could recommend to these people that they visit with a certified CPS technician who can check the tightness of the straps to see if they are just right or too tight.

      1. What about a premature now 7lb baby that is eight weeks old. Her shoulders and neck are compressed to me?

        1. Hi Tracy, I know with premature babies it looks like they are going to get lost in that seat because they are so small. And you still need to properly adjust the harness on them.

  2. My toddler keeps moving the chest clip down to his belly. I can’t get it to stay at armpit level, is this a problem with all car seats or just mine? It’s a Costco brand.

    1. I can’t think of a brand in the US where the chest clip doesn’t move so it would be a problem with all brands if that is what your child likes to do. There is a product by Merritt Manufacturing (they produce car seats for children with special needs) that would help keep the chest clip in place. You can find that here:

  3. How do I get a toddler in and out of the car with no coat on during minus weather conditions? The only way I’m thinking is to remove the coat when being placed in the seat and putting on when coming out

    1. Yes, that is what we would recommend. The child should have a coat going to and from the car but not in the car seat. Take the coat off, buckle in and adjust the straps, then put the coat on backwards over the straps. Do the reverse when getting out.

  4. Are there any stats that you are aware of that prove that correct usage of a car seat harness can decrease risk of injury or death vs poor car seat harness usage? Wanting to share the importance of “correct buckling” with family and hoping some stats will help prove the importance of taking the time to buckle them in right! Thanks in advance!

    1. I don’t know of any statistics specific to correct car seat harness use. On a quick search I couldn’t find any numbers but there is this quote from the Guardian which tested various common car seat mistakes: “Hynd, who works as an adviser on car seats to the European Commission and represents the UK on working groups for child seat safety, said this would have resulted in head injuries. She said the slackness of the harness would have prevented the seat spreading the force of the crash over the child’s body and reducing injury. “Too much slack in the harness means that the child will be caught later in the crash, because the harness doesn’t have time to absorb the energy,” she said. In some cases, it can even result in the child being ejected.”

  5. I am trying to find out where to position the harness covers?? I’ve tried looking it up and looking in the owner’s manual. I have a Graco and my daughter is 1 month old in the rear facing seat. The car seat comes with harness covers and I don’t know where they’re supposed to be on shoulders all the way up below, etc… and why can’t I find the answer if they come with the car seat?!?! Makes me wonder…

    1. Are they sewn on or detachable? Usually they are supposed to be up by the neck. In some seats, the manufacturer says not to use them for a newborn. Which Graco seat do you have? For instance, Graco SnugRide ClickConnect 35 just briefly says some models come with inserts to be used for extra support and comfort and has a picture that includes the harness strap cover on page 25 but I couldn’t find any specifics written any where else.

  6. If a child is too big for a 5 point harness carseat and is put in one anyways what harm can this do to the child if a wreck was to occur.

    1. If the child is bigger than the specifications noted on the car seat, there is potential the car seat could fail in a crash thereby not actually restraining the child. I’m not sure any manufacturer has crash tested their car seats with a larger than specified crash test dummy to determine what would/could happen.

  7. Good solution for children who like to unbuckle or move chest clip would be to button a button up shirt over the car seat!

  8. My daughter is 16 days old. Im trying to get the straps that go across her hips, to be tighter. Either those don’t tighten or something is awry. Any thoughts on this?

    1. Hi Dawn, Try pulling the straps from around her hips up so the slack is by her shoulders before tightening the harness straps down.

  9. Ok so snug as a bug I get that. But what about so snug it hurts the child’s (boy) privates? My sister ALWAYS makes my son’s that snug and tells him he is lieing and to get the f over it. I’m concerned because that area is very sensitive

    1. Hi Bridgite, Check and see if you can adjust the crotch strap on your seat. Many seats have different settings so as the child grows it can moved further out. The crotch strap should be at or in front of the crotch area. Perhaps if you can adjust that it won’t hurt that area even when it’s pulled nice and snug so it passes the pinch test.

  10. Hi! My daughter gets the crotch buckle to poke into her stomach. I’ve tried repositioning and adjusting straps to no avail. If a picture will help I can provide one via email.

    1. Some more information (seat, child’s age, weight, height) and a picture would be helpful. Please use the contact form and we’ll send an email you can reply to with a picture.

  11. How can I keep the hip straps from pinching the skin on my child’s legs? I’m am so careful each time but it always manages to get pinched near the side of the buckle.

    1. I can’t say I’ve ever encountered this problem or I’m not understanding fully. Do you mean when you are buckling the 5-point harness, it is pinching her legs? Are you pulling the harness tight before buckling? I recommend leaving the harness strap loose when buckling, then pull it tight (so you cannot pinch the strap as shown), then adjust the chest clip.

    1. Hi Cindy, The harness straps need to be tight enough that you cannot pinch the webbing as seen in the photo above. It’s possible it could be too tight but there could be other reasons he screams in his car seat. Some children just don’t like any confinement; some children could be irritated by a tag in their clothing that only seems to bother them while in their car seat. At 7 months he obviously can’t explain why he’s upset. If you think the straps are too tight, you can try loosening them as long as they remain tight enough that you cannot pinch the webbing.

  12. My wife is always untightening and tightening the straps every time we take my daughter in and out of the car. Should we not just set the tightness where we want it, and then all we have to do is buckle and unbuckle each time?

    I’ve seen numerous articles about shoulder strap positioning, but where should the lower straps be resting?

    1. Hi Mike, Many parents find it easier and more comfortable for the child to get the child in and out of the seat by loosening the straps.

      About which lower straps you are asking? The harness straps are all one piece. The lower part should be at the child’s hips/thighs. The vast majority of seats do not have any adjustment on that part of the harness strap. Some seats do offer adjustment of the crotch strap. If that is the strap you are referring to, it should be in the slot closest to the child’s groin.

  13. Hey !

    Thank you so much for these great tips.
    I will definitely follow these instructions. Keep writing.


  14. Is there such thing as positioning the shoulder straps too low while reset facing?? My daughter always seems to sink in her seat causing the straps to push the ‘at’ in the “at or bellow the shoulders” rule. Sometimes they seem to be a centimeter above and sometimes they’re at, other times below. I’ve tried repositioning the crotch buckle, it has two position settings, but the closest positioning is under her butt and then in the second it seems correct but then still have the shoulder strap problem. I try to loosen and tighten properly every time I buckle her in to make sure it’s all set correctly. She just seems to be able to slouch in her seat. 34 inches tall and 24th for an idea.

    1. Hi Hannah, Not that I’ve ever heard. But you do want it below or at her shoulders rear facing so in a crash her shoulders would be cradled. I would have to see her in her seat and see the other harness slots to see if moving the straps down would be helpful or if they are just fine where they are. Maybe it would be beneficial to visit with a local Child Passenger Safety technician so they can see your child in her car seat in person.

  15. We live in Maine and I am trying to figure out if it is safe to put my son who is about 62 lb in a high back booster with the top of the five point harness straps strapped and then the seat buckle over him. He is four and autistic and doesn’t stay in a regular booster seat. It’s too expensive at the moment to buy a specialty car seat. I just need to know if this is actually safe to do or not because it’s about the only way that I can get him around right now. Thank you

    1. Hi Taniesha, Combination seats (harness seat that turns into a booster, sometimes called a harness booster) is not tested or meant to be used with the harness straps when being used as a booster.

  16. In your article is says “…side impact crash testing shows when the chest clip was missing but everything else was used correctly, the child’s head experienced an extra two inches of side movement and a shoulder slipped out of the harness.” I would like to read more of this study, can you provide me this reference?

    1. Hi Ruellen, The statement surprised me when I read it again, which is probably why I added it in the first place. I believe it came from a Continued Education Unit for recertification as a child passenger safety technician which is why it wasn’t linked but I’m currently having a hard time finding the unit so I’m going to remove this for now and keep searching for it.

  17. Hi. I am a full time nanny for a family with 2 small children and am looking for advice on how to tell mom and dad they are strapping their newborn (he’s almost 8 weeks old) into his infant carrier incorrectly. I obviously don’t want either of them to feel I’m trying to correct them or make anyone feel stupid bc they’re both extremely smart people but I cannot pretend I haven’t noticed and heaven forbid something happen to him. The problem is they are putting his legs inside the lower straps and not over his pelvis which is the ONLY way I’ve never known it to be used. Another way to describe it would be his arms and legs are all inside the strap if that makes sense. I just feel there is nothing really holding the lower half of his body down into place. Am I incorrect? I’ve taken care of children my whole life and have never seen it done this way. If so, wouldn’t it be really dangerous to strap him in, in such a way? I just wanted to clarify before saying something to them both. Thank you!

    1. Hi Jen. Sorry for the delay. I’m having trouble picturing how he is harnessed if his legs are in but the pelvis is not. In any case, if the harness is not being used correctly, then it’s not a safe use and the child could experience additional injury in a crash. Studies show 96% of parents think they are using car seats correctly but most are not. They just don’t know what they don’t know. It can be a difficult topic to approach, especially as an employee, but parents want their babies to be safe. Is the car seat manual on the car seat? Maybe you can show them pictures in the manual of how to correctly harness the child in that car seat.

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