Could not installed it properly
Child seat for vehicle

Preface of the research

I have a two years old daughter.

I have been using a baby seat, which her mother and I have bought it shortly after her birth, when we drive. When my daughter was a year and half, we bought a different child seat because the baby seat got too small for her. My daughter really likes her new child seat, and she comfortably sits on it when we drive.

Well, there is a study called “National study for status of use of child seats, which National police agency carries out every year with JAF (Japan Automobile Federation), and as always, the result of this year has been released to public.
http://www.jaf.or.jp/safety/data/childkek.htm

From the study result, the usage rate of children under 6 years old, who are obligated to use the child seat, is 54.8%. Because the usage rate of children who reach to around 5 years old drops at once, the overall usage rate is low. And what surprises me the most is that 63.4% of those who use child seat have not been able to install the seat properly. The most among those improper installation is explained as "seat belt is not fasten enough"

When I first see this study result, I’ve thought “ No matter how you look at it, this is too much”, but then there has been a time when I have made a mistake in install the child seat, so it can say that this is not an exaggerate number.

If so, in what place will user get stuck when he/she actually installs the child seat, and why they cannot install it properly? We have decided to check those by conducting a usability test.

Conduct usability test

(1) A child seat used in the test

For evaluation target product of this usability test, I have used a child seat, which I have bought last year for my daughter. This child seat is the following product:

• Attach with harness (shoulder belt)
• Target age: one year old to around 10 years old(Weight between 9 kg to 36 kg)
• Feature: it can be used for long time with in child mode for the weight between 9kg to 18kg, and in junior mode between 15kg to 36kg.

There is an assessment called child seat assessment, which is conducted every year by Land, Infrastructure and Transportation Ministry.
http://www.mlit.go.jp/jidosha/anzen/02assessment/child_h20/index.html

The child seat I have used for this study has received more than 4 pts out of full 5pts in use performance evaluation of 2007 assessment for "instruction manual" and "installation", which tells that the product has relatively high marks.

(2) Participants' profile

We have asked 3 staffs of ours to be participants for this usability test. The following is a profile of the 3 participants.

All three participants do not have a child, and have never used child seat before. I have asked them to perform the tasks based on the image they have by seeing and hearing about the child seat.

(3) Test environment and tasks

With the following contents, I have given instructions about the test environment and tasks.

A) About your car

• Matsuda MPV
• 2500cc 5 doors 7 seats
• There are SRS airbags on driver’s seat and front passenger's seat.

B) About your child

• Girl born in April of 2007
• 82 cm of height and 11 kg of weight

C) About the child seat you have purchased

• Target age: about 1 year old to 10 years old
• Target size: 9kg to 36kg

D) Task instruction

You have a child who has just turned 2 years old.
You have purchased a child seat for your child to set in your car.
You have just taken the child seat out of the box, and now you are going to install the seat to your car.

Please install the child seat in the vehicle.
After installation in the vehicle, please put it in the condition where you can drive your car with your child. (You do not need to sit on the driving seat)

At the test, by assuming he/she has actually just purchased the child seat and is going to install it in the car for the first time, I have provided the target child seat and the instruction manual as just purchased condition to the participants. All have performed the tasks by looking at the instruction manual.

Able to install it properly?
(test result)

First, let’s see whether the participants eventually have been able to install the seat properly by themselves.

A and C installed the seat in a clearly problematic way.

B was able to install it to the level where there was no problem in use. However, from the post-task interview, it turned out that he did not understand the function/specification correctly.

The places they got stuck
(test result)

Here are some main issues that have been occurred in the process of installation. (Both pictures below are reproduction pictures)

(1) Tend to use it by not adjusting the height of shoulder belt (A).

[Proper procedure]
Before install the child seat in the car, put the child in the seat and adjust the height of shoulder belt to the child's shoulder. In the initial state, the shoulder belt is through the belt hole of the height that is lower that 2 years old child.

[Description]
A read the explanation of this procedure in the instruction manual, however because he did not understand the need of this procedure, he skipped the procedure itself, and ended up putting the child in the seat with the condition where the height of shoulder belt was not lined up with the shoulder height (lower than the child's shoulder). With this state, even he fastened the shoulder belt, the shoulder pads were not attached to the body, and could not fasten appropriately, or giving unreasonable force applied to the child's body.

(2) Unable to anchor the child to the car (C)

[Proper procedure]
Place one knee on the top of the seat and use weight to fully compress the car, pull out the slack of the seat belt, and lock the seat belt.

[Description]
By following the procedure in the instruction manual, C was able to do up till taking up the slack of the belt by putting her weight down, but because it was difficult for her to lock the belt while putting her weight, she has locked it without putting her weight, and the belt got the slack again. The seat was fixed to a certain degree, but because the seat was shaky widely when we swung it a bit stronger. This will move the child seat greatly when an accident occurs and the child might get hurt.

(3) Unable to distinguish the type of seat belts (all)

[Proper procedure]
At the beginning of the procedure, the instruction shows how to distinguish the type of seat belts regarding their function. By reading the instruction, one should actually work with the seat belt, and distinguish their types to find out the proper way to install which is suited for that particular type.

[Description]
There are several types of car seat belt, such as with or without auto winding unit, or with or without lock mechanism in case of emergency (there is a similar one as the table below in the instruction manual of evaluation target product).

The point here will be ELR and AELR.

ELR(emergency locking retractor)is a common seat belt that is equipped in most cars today. In other hand, AELR is also called "seat belt with child seat fixed function", and addition to the function of ELR, it also has a function, which makes it easier to install when fix the child seat. The seat belt of back seat of the car we've used for the test is AELR.

A read the instruction manual about the types of seat belt carefully, and operated it, but misunderstood, as the seat belt in the car is ELR. Also other 2 performed the tasks without reading the determination procedure itself of the types of seat belt.

Fact is, since there is not much of a difference in ELR and AELR regarding the effect on installation of child seat, even they have failed in determine the types of seat belt nor have not determined at all, they eventually will be able to install the child seat properly, and will not cause a big problem regarding the safety, but because the function that is built-in the seat belt of the car will not be used effectively, they will not be able to enjoy the advantage of the function (make it easy to install child seat).

Incidentally, although I did not show them the instruction manual of the car at this test, there was no word of AELR on the explanation of seat belt in the manual.

(4) Tend to set it up with twisted shoulder strap (All)

[Proper procedure]
When adjust the height of shoulder strap, pull out the strap once, and put it into the correct slot. At this time, check the direction of the slot tag for fasten right and left shoulder straps, and thread the straps through the slot of the child seat in the proper direction which will not make twisted strap when fasten.

[Description]
All 3 participants threaded the strap through the slot without checking the direction of neither the straps nor slot tag. They then noticed their mistake when they tried to put the child in the seat after going through the task, and had to redo the installation of should strap.

You will notice this mistake when you place your child on the seat, so you may not be using it as it is, but if you notice it after the child seat is fixed to your car, and you are going to put your child in the seat, you may end up redoing from the installation of the seat, and it will be very troublesome work.

(5) Unable to understand the purpose of what they are working on (B and C)

[Proper procedure]
When use it in child mode(the mode of the seat for child who weighs up to around 18 kg. It is a usage to fix the child seat to the car seat before place the child in the seat), the following procedure is explained on the instruction manual

1. Preparation of car seat
2. How to adjust angle of the child seat
3. How to use head pad
4. How to decide the place of slot for shoulder strap.
5. How to put a child in a seat
6. How to install child seat in a car
7. How to check the completion of the installation

[Description]
Explanation for each work is relatively clearly written, but because there is no clear notification about the purpose of each task, it seems that participants cannot imagine the aim of the work (how it will be done), and feel uncomfortable.

Specially, “4. How to decide the place of slot for should strap” is hard to imagine the aim of the work, and the work itself is complicated, participants may feel more nervous about this.

Impression of the research

By checking freshly about how to install the child seat, because it is a safety involved equipment, I am surprised to see many points to notice, and that although every of those points are important, it is difficult to get those importance from the instruction manual of this product we have used for this research. As it is now, it seems that it is depending on the users knowledge and comprehension.

Also, child seat itself still has rooms for improvement, because of difficult mechanism to understand, and also parts that require more effort and time.

By using it in daily basis, if you do not replace the child seat between cars, you will be continue using the seat as it is after the first installation. That means if you have installed it improperly, you do not get much chance to fix that, and will be using it in false and dangerous state. To avoid the situation like this, the usability such as easy to install and clear instruction manual will be an important factor that colligate directly with the safety.

When select a child seat, it is important to select the one that is high in the safety assessment process, but you should also be aware about whether it is easy to install, for the safety. Lastly, to those who are already using a child seat, please check how it is installed.

Created in 2009.10.02