**3.1 Configurations of children's carriages traveling inside the bus**

Taking into account the dynamic analysis of the transport configurations using different ChC models and considering the interior designs of passenger compartment of large capacity passenger vehicles (M3), the areas where the ChC would be traveling and the most appropriate restraint system for each one of them were identified and characterized. In that sense, three possible zones can be identified inside the passenger compartment of the transport vehicle, as shown in **Figure 9**. These areas have the following characteristics:


*Passive Safety of Children Carriages on Busses DOI: http://dx.doi.org/10.5772/intechopen.90613*

#### **Figure 9.**

*Characterization of the zones for the location of the ChC unfolded during transport in M3 vehicles (source: [14]).*

• **Zone 3**: The central area of the bus between the two zones 1 and 2, in which the ChC and the accompanying adult could travel along the bus sidewall. In that case, it is necessary to use a specific restraint system to hold the ChC in their place following the instructions provided by the transport operator. The child must have the harness attached. The ChC should apply the wheel brakes and should be traveling facing rearward.

As a result of the experimental tests, it was concluded that, among the three zone alternatives, the safest for traveling with ChC is Zone 1, provided that it is not occupied by a wheelchair user, and where the ChC is directly supported on the backrest facing rearward, with the wheel brakes applied and secured by means of a safety belt, that some busses already have incorporated. **Figure 8** shows an example of this configuration.

#### **3.2 Strength analysis for children's carriage restraint systems**

Finally, considering the value of the maximum accelerations obtained in the experimental field trials, it was possible to establish the order of magnitude of the forces that the restraint system should withstand to retain the ChC and its occupant. For this calculation, the accelerations generated when the ChC suffered a fall against the floor or the interior parts of the vehicle were not taken into account. The results were obtained considering the total mass of the ChC and its occupant, the maximum deceleration suffered by them during the braking test (which is the most unfavorable). Thus, the maximum force that the restraint system would have to withstand occurs in those cases in which the heaviest ChC is used, reaching the value of 782.46 N. If a safety factor of 2 is applied to the ChC-user set [9], it can be stated that the maximum load that the restraint system would have to bear to withstand the maximum deceleration generated during a braking force would reach the value of approximately 1565 N (1.56 kN).

Analyzing these experimental results, and taking into account that for Zone 3 (located between the backrest of the area reserved for wheelchairs passengers and the first row of rear seats), it was verified that it does not exist currently in the market safety systems designed to facilitate the retention of ChC when traveling in high capacity transport vehicles (M3). So, a new restraint system designed to hold the ChC unfolded during transportation in road vehicles was developed.

**Figure 10.**

*Scheme of patent ES2403161 defining the operation of a folded-unfolded passive restraint system for the transport of ChC in M3 vehicles (source: [21]).*

The new safety system was registered by the Polytechnic University of Valencia and the Polytechnic University of Madrid, through the Spanish Patent ES2403161 [21]. The originality of this invention is that, unlike other restraint systems applied to assure the mobility of wheelchair users in public transportation vehicles, the passive restraint system developed prevents involuntary displacements of ChC, not only longitudinally but also laterally. **Figure 10** shows a simplified scheme of the assembly, which presents the device when it is in the rest position (folded) and when it is used with the ChC in transport position (unfolded). The passive restraint system can be used simultaneously with wheelchair users according to current regulations (UNECE Regulation R107). The safety system has been manufactured in lightweight materials and is able to withstand forces in impacts of up to *2 g*.

### **4. Safety requirements of children carriages traveling on busses**

To date there have not been many experimental works aimed at obtaining the dynamic behavior of ChC when traveling in road transport vehicles subjected to low speed impact. One of the few references of this type of research was carried out in the development of the ASUCAR project. This project was the first scientific study that has been carried out in Spain in the field of transportation safety of ChC on busses, with no precedents for research projects similar in the rest of Europe [22]. The ASUCAR project continued in a second phase called ASUCAR-2<sup>2</sup> , whose main

<sup>2</sup> The ASUCAR-2 research project, *Validation of the usability of a retention system for the safety of children's carriages in public transport vehicles*, was funded by the Polytechnic University of Valencia in the INNOVA 2012 Program (Contract No. 20120579).

### *Passive Safety of Children Carriages on Busses DOI: http://dx.doi.org/10.5772/intechopen.90613*

objective was the strength and usability validation of the safety system developed to facilitate the restraint of ChC in transport vehicles [23, 24]. The design and manufacture of the new safety system was experimentally validated by performing a battery of representative tests of low speed impact (≈ 20 km/h), with an equivalent deceleration level of *2 g*.

As the Annex 8 of UNECE/UN R107 does not explicitly define any dynamic test to verify the behavior of the ChC under situations of impact, this research was considered an experimental work that could be used for defining the technical requirements for testing the structural behavior of this type of safety systems. In that sense, during the ASUCAR-2 project, a battery of six impact tests were developed on a sled-test platform, whose characteristics were defined based on the results obtained in the first phase of the project. During these tests different prototypes of safety systems were used for the ChC. First, a backrest panel was selected, representative of those used in urban busses, which complied with the technical requirements of UN/ECE Regulation R107. The backrest was provided by the Municipal Transport Company of Madrid. In total, three different prototypes of the safety system developed were used, inspired on the design shown in **Figure 10** [21]. The characteristics of each prototype tested were based on the following aspects:


The ChC tested were selected among the most representative models of the market (**Figure 11**), according to the results obtained in previous phases of the ASUCAR project [9, 12], and were characterized by:


The sled tests were designed to reproduce an acceleration up to a defined speed (V ≈ 20 km/h) and programmed to stop in a controlled manner with a deceleration of *2 g*, reproducing the deceleration pulse shown in **Figure 11**. Testing took place between July and September 2013 at the facilities of the University Institute of Automobile Research (INSIA), belonging to the Polytechnic University of Madrid (Spain). The ChC restraint system and the WhCh back-restraint were installed on a representative module of the space reserved for a WhCh user, dimensionally and geometrically, similar to that of a standard urban transport M3 vehicle (**Figure 11**). All the tests were carried out with the carriage facing rearward. An accelerometer was installed on the platform module to measure the longitudinal deceleration, according to SAE J211 [25]. All trials were recorded with two high-speed cameras (1000 fps) and a third conventional camera at 30 fps. In

**Figure 11.**

*(A) Deceleration pulse applied during sled tests. (B) Configuration for sled-test platform (source: [24]).*

the trials two types of dummies were used to represent the occupants of the carriage:


These dummies were approved to comply with UNECE Regulations R129 Rev.00 (2014) and R44 Rev.04 [16] for the approval of child safety systems. At the time the study was conducted, there was no international regulation defining the criteria for damage to be applied to Q1 dummies. Therefore, the damage criterion used for this dummy was defined based on the information in UNECE Regulation R94 Rev.01 [26], applying the parameters defined in the work of Mertz, Irwin, and Prasad [27].

The different test configurations were designed to validate the structural behavior of the safety systems developed and analyze the usability of different configurations of the space reserved for wheelchair users and ChC, under low impact conditions. The terms *correct use* and *misuse* as per defining the ideal mobility conditions of ChC during transport were established. All testing was representing worst-case situations regarding ChC model and travel orientation, direction of impact, brakes applied to ChC, and distance from ChC to backrest panel. The configurations of the dynamic impact tests performed are shown in **Table 2**.

The damage criteria for children to define the validity of the results were established by scaling the factors described in [27]. These scale factors had previously been used as reference values in UNECE Regulation R94 Rev.01 [26] for adults of average size as well as in the Federal Motor Vehicle Safety Standards (FMVSS) regulations. The "limit values" established in these regulations, and defined in the analysis of the results of this research, correspond to the probability of generating damage to the different parts of the body. An analysis of the results obtained in the dynamic impact tests allowed us to reach a series of conclusions about the *correct use* and *misuse* configurations in the road transport of ChC. These

*Passive Safety of Children Carriages on Busses DOI: http://dx.doi.org/10.5772/intechopen.90613*


## **Table 2.**

*Configuration for sled testing of ChC (source: [24]).*

conclusions were drawn from the battery of tests carried out in the ASUCAR and ASUCAR-2 projects and can be summarized as follows:

