Floor anchorage load and safety space for adult wheelchair users during a crash

IRBM 31 (2010) 289–298

Original article

Floor anchorage load and safety space for adult wheelchair users during a crash Effort d’ancrage au sol et espace de sécurité pour les utilisateurs adultes de fauteuils roulants lors d’une collision F. Bermond a,b,∗,c , X. Attali d , C. Dolivet a,b,c b

a Université de Lyon, 69622 Lyon, France INRETS, UMR T9406, LBMC, 25, avenue Fran¸cois-Mitterrand, 69675 Bron cedex, France c Université Lyon 1, 69622 Villeurbanne, France d CERAH, 57140 Woippy, France

Received 4 October 2010; received in revised form 4 October 2010; accepted 6 October 2010 Available online 26 November 2010

Abstract Over the last 20 years in France as well as generally in Europe and also in North America, the integration of disabled people into society has become a more and more pressing issue. Work is in progress to increase the safety level of wheelchair occupants up to becoming equivalent to that of able-bodied road vehicles occupants. Present world practices are that wheelchair occupants who are unable to transfer to a vehicle seat for transportation remain in their wheelchair, which is secured to the vehicle floor using tie downs, and the occupant is restrained in the wheelchair. The aim of this paper was to perform a series of crash tests to make sure that the current standards are suitable to identify possible failures in safety in the restraint systems intended for wheelchair users. To date, there is no specific regulatory criterion related to floor anchorage for wheelchairs in vehicles during a crash. At a 48 km/h crash test, loads reached 30 kN on rear anchorage, and 13 kN on shoulder belt. Also the kinematics analysis of the wheelchair user during impact pointed out dimension of his safety space. © 2010 Elsevier Masson SAS. All rights reserved. Keywords: Transportation; Safety; Crashworthiness; Restraint systems; Impact sled test; Occupant protection; Body in white crash test

Résumé Au cours des 20 dernières années en France et en général en Europe et en Amérique du Nord, l’intégration des personnes handicapées dans la société est devenue un enjeu de plus en plus important. Les travaux en cours visent à accroître le niveau de sécurité des occupants de fauteuils roulants jusqu’à devenir équivalent à celui des occupants valides des véhicules routiers. Dans le monde, les pratiques actuelles pour les occupants de fauteuils roulants qui ne sont pas capables de se transférer au siège du véhicule pour le transport, demeurent dans leur fauteuil roulant qui est fixé au plancher du véhicule à l’aide d’arrimage, et l’occupant est retenu dans le fauteuil roulant. L’objectif de cet article était de réaliser une série de crash tests pour s’assurer que les normes actuelles sont appropriées pour identifier les éventuelles défaillances de la sécurité dans les systèmes de retenue destinés aux fauteuils roulants. À ce jour, il n’existe pas de critère réglementaire spécifique des systèmes ancrages au plancher pour les fauteuils roulants dans les véhicules lors d’une collision. Une analyse détaillée des charges supportées par l’ancrage au plancher est incluse. Lors d’une vitesse de 48 km/h crash test, les charges ont atteint 30 kN ancrages arrière, et 13 kN sur la ceinture d’épaule. De plus l’analyse cinématique de la personne en fauteuil roulant lors de l’impact a permis d’estimer la dimension de son espace de sécurité. © 2010 Elsevier Masson SAS. Tous droits réservés. Mots clés : Transport ; Sécurité ; Résistance aux chocs ; Système de retenue ; Essai de choc avec chariot ; Protection des occupants ; Essai de choc dans caisse de véhicule

∗

Corresponding author. E-mail address: [email protected] (F. Bermond).

1959-0318/$ – see front matter © 2010 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.irbm.2010.10.003

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1. Introduction A lot of people in the world have mobility problems severe enough to require either part-time or full-time use of a wheelchair. From children to senior citizens, wheelchairs are a necessary part of daily life. Article 45 of French Law no. 2005-102 of 11 February 2005, about the equality of rights and chances as well as the involvement and citizenship of disabled people, stipulates that public transport shall be accessible to passengers with disabilities and reduced mobility within 10 years of the promulgation of the law. Today, various countries have legislation requiring physical accessibility in public transport. Also wheelchair users (WCU) take private light vehicles (LV) or minibus. Current world practices are that WCU who are unable to transfer to a vehicle seat for transportation remain in their wheelchair. The use of safety belts in transport has proved useful for a long time now. In more and more countries, all vehicle passengers should wear the safety belts provided or any other protection devices intended for their safety, irrespective of the seat they occupy in the car. Generally speaking, restraint devices can be used without any difficulty by most of the population; however, in some cases, these may prove unsuitable for people with disabilities, which is the case of WCU. So the WCU is secured to the vehicle using wheelchair tie down and occupant restraint systems (WTORS). These systems should provide the WCU with a safety level similar to the rest of the passengers. In-depth investigation of motor vehicle crashes (Schneider et al. [1]) points to a need to properly secure wheelchair passengers. These findings show the necessity for improving the restraints system, which means to evaluate the vehicle anchorage loading during a crash. The article, from Shaw [2], reviews the issue of establishing appropriate protection on buses for riders in wheelchairs. The author reports on a study that examined injury-producing events aboard large transit buses; the data was taken from three regional databases: the Ontario Ministry of Transportation (MOT) database, the New York State Department of Transportation (NYSDOT) database, and the Washington State Transit Insurance Pool (STIP) database. The study was undertaken as an attempt to better understand the potential risks and required protection for WCU. The study found that few injuries and fatalities occur on large transit buses. However, examination of these relatively few injury-producing events provides information in terms of acceleration/deceleration magnitude and direction. Low acceleration/deceleration, or low-g, events such as those involving abrupt braking or turning occur frequently and are associated with approximately half of onboard passenger injuries. Most of the injurious events involved the bus rapidly decelerating because of frontal impacts with another vehicle or roadside object. The author calls for further study to determine the magnitude and frequency of high-g events and to determine the level of protection needed for wheelchair riders in the transit bus environment. The author also supports the development of easier-to-use

safety systems that secure and restrain wheelchairs and their riders. Senin et al. [3] have shown experimental evaluation of the WCU protection under different impact conditions using commercial wheelchairs. This work evaluated different foldable wheelchairs regarding their behaviour under three impact conditions (front, rear, and side) using different WTORS. The structure integrity of the wheelchair can be unsatisfactory. In general terms, it can be concluded that the protection of the wheelchair occupant under the different impact conditions was not achieved in the tests carried out in this work, mainly due to the failure of wheelchair structure and the use of inadequate restrains systems. Le Claire et al. [4] carried out a work on behalf of the UK Department for Transport by Transport Research Laboratory (TRL Limited). The aim of the work was to assess the safety of WCU when being transported on all M category vehicles (Motor vehicles with at least four wheels used for the carriage of passengers). The work found that the heads and necks of WCU were particularly vulnerable. Further recommendations from the work were that an upper anchorage location for diagonal restraints is preferable to a floor mounted location and that the restraint anchorages should meet more rigorous strength requirements. Consequently the WCU crash protection has to be assessed. Also different standard have been developed. The Standards ISO have been developed by the International Organisation for Standardization (ISO) to evaluate, the effectiveness of WTORS in motor vehicles (ISO 10542, [5]) and the wheelchair crashworthiness (ISO 7176, [6]). The literature related to crash configurations (side impact, rear impact, roll over), have revealed insufficient knowledge about the behaviour of this restraint system in case of crash, (Kim et al. [7], Fuhrman et al. [8]). Also the deformation of the vehicle floor should be recorded accurately. The objective of this paper was to check the protection offered to the WCU by using wheelchair and WTORS following the current standards. To identify possible failures a series of crash tests, on a rigid platform and in body in white (BIW) was carried out. The detailed analysis of the loads supported by the floor anchorage, the analysis of the WCU kinematics and the WCU safety space during impact were presented. 2. Material and methods These tests were carried out using crash test catapults (Safety test unit, UNEX INRETS). The first series, using a rigid platform on the trolley, enabled the accurate measurement of the loads on the floor anchorage. This testing campaign was performed using an electric catapult of intermediate capacity (800 kg at 60 km/h) enabling the propulsion of a decelerated trolley. The deceleration system enables programming multiple deceleration levels with satisfactory repeatability. The trolley is fitted with several polyvalent interfaces for the assembly of the equipment to be tested (Fig. 1). The second series closer to the reality and performed using a BIW investigated different new and extreme configurations as well as the vehicle floor behaviour.

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Fig. 1. Testing campaign – first series – rigid platform on trolley.

Fig. 3. Rear tie down position of non standardized wheelchair before test (UFR 101).

The testing campaign was performed using a large catapult fitted with a decelerated trolley. The trolley carried the BIW of a light duty vehicles (LDV). The use of the BIW of this type of vehicle was justified by the issue of anchorage resistance in the floor of vehicles weighing less than 3.5 tons. A LV (< 2 tons) was dismissed since these vehicles are often seriously modified in particular regarding the bodywork so as to host the height of WCU. Floor reinforcement pieces can be installed more easily. Front beams have been shortened and reinforcement pieces added. The roof was cut to take into account the vertical movement of the head and to be able to follow the movement. The BIW was fixed on an interface to be then placed on the test trolley. In addition, floor reinforcement pieces were made to support the loads of the anchorages for the wheelchair and occupant belts without distortion of the floor. This BIW was expected to carry out several tests (Fig. 2). The content of the tests takes inspiration from the requirements of ISO 10542 [4] and ISO 7176 [6] Standards. Regarding the crash test dummy, we have in addition complied with the requirements of the Geneva Regulation 94 [9] with a view to

compare with the requirements for able-body occupant in car seats. 2.1. Detailed information regarding the use of the restraint systems chosen in terms of wheelchair and occupant anchorage 2.1.1. Securing the wheelchair The wheelchair is placed in forward-facing position. The wheelchair’s front straps are connected to the floor anchorage systems and to the wheelchair on the space indicated by the standardized label (expect for non standardized wheelchair). Strap length is adjusted in order to centre the wheelchair in position and comply with angles between floor and straps (60◦ as a maximum). Subsequently, the wheelchair’s rear straps are connected to the floor. These must be adjusted at an angle of 45◦ as a maximum. The assembly directions are complied (left and right straps). Straps are pulled on using the semi-circular ring and fastened in the buckle. 2.1.2. Securing the occupant The lap belt is fixed onto the triangular rings of the upper part of the wheelchair’s back anchoring strap (Fig. 3). The lap belt should go through the inside of the side panels and armrests. The ring for the shoulder belt is fixed onto a catch on the lap belt. The strap for the shoulder buckle is placed opposite the upper anchorage of this shoulder strap to make sure that the lap belt is positioned correctly. Two different types of restraint belt, static and retractor, conform with ISO 10542 [5], were used for securing the wheelchair and the occupant. 2.2. Technical description of the wheelchairs under test

Fig. 2. Testing campaign – second series – body in white on trolley.

The characteristics of the wheelchairs were presented in Table 1. A first, non-standardized wheelchair (ISO 7176, [6]) was tested, only during the first test, to check its behaviour in case of impact as compared to standardized wheelchairs.

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Table 1 Description of the wheelchairs tested.

14

A B

Description

Total weight (kg)

Non standardized Standardized manual Standardized electric SWC

C D

21 35.5

Seating width (cm) 43 45

106

46

85

41

Deceleration, g

12

Wheelchair code

10 8 6 4 2

SWC: Surrogate wheelchair.

0 0

10

20

30

40

50

60

70

80

90 100 110 120 130 140 150 160

Times, ms

The two others were standardized wheelchairs. A fourth wheelchair was also used as a Surrogate WheelChair (SWC), as defined in ISO 10542 [4] standard, to test the robustness of restraint systems. It was used for the evaluation of test configurations without the wheelchair behaviour interfering. The main feature of this wheelchair was that it could be reused and was almost non-deforming. It was developed by Research Centre for Disabled People Equipment (CERAH). 2.3. Test specifications 2.3.1. Testing campaign The deceleration corridor during impact was that of ISO 10542 [4] and ISO 7176 [6] standards (Fig. 4) whereas that for United Nations/Economic Commission for Europe (UN/ECE) Regulation R80 [10] (Fig. 5) for public transport M2 and M3 category vehicles was also used. Vehicle categories are defined according to the following international classification: • category M1: vehicles used for the carriage of passengers and comprising no more than eight seats in addition to the driver’s seat; • category M2: vehicles used for the carriage of passengers and comprising more than eight seats in addition to the driver’s seat, and having a maximum mass not exceeding 5 tons; • category M3: vehicles used for the carriage of passengers and comprising more than eight seats in addition to the driver’s seat, and having a maximum mass exceeding 5 tons. 32 28

Deceleration, g

24

deceleration superior to 20 g for 15 ms

20 deceleration superior to 15 g for 40 ms

16 12 8 4

time period superior to 75 ms

0 -4 -20

0

20

40

60

80

100

120

140

Times, ms

Fig. 4. Acceleration/deceleration of the impact sled, from ISO 10542 and 7176.

Fig. 5. Acceleration/deceleration corridor of the impact sled, from UN/ECE Regulation 80.

The acceleration/deceleration of the impact sled shall stay within the area and exceed the indicated levels for the specified continuous and cumulative time periods (Fig. 4) or inside the corridor (Fig. 5). A Hybrid III 50th percentile crash-test dummy (1.75 m–76 kg) was used (except for the first test during which a Hybrid II 50th percentile crash-test dummy was used). Five tests (from UFR101 to UFR105) were carried out on the rigid platform and six tests (from UFR106 to UFR111) in the BIW. The test specifications are described in Table 2. The positioning of floor anchorage was as follows (Fig. 6): • spacing between rear and front anchorages: 1300 mm; • spacing between right and left rear anchorages: 400 mm; • spacing between right and left front anchorages: 570 mm. These were unchanged for all tests. For feasibility reasons, the ISO 7176 [6] Standard requirements were not scrupulously complied with as regards the anchorage point of the thorax belt, which was positioned 300–400 mm behind the shoulder. The leftward movement, in relation to the vertical axis of the dummy, is of 300 mm. The height, in relation to the shoulder, is 140–205 mm. On the other hand, the angle of the shoulder belt compared to the horizontal axis is the same i.e. 55 ± 2◦ . The brakes of the manual and powered wheelchairs were engaged. The SWC does not have a braking system, so it was not blocked. 2.3.2. Physical measurements Embedded data acquisition systems allow the following dynamic measurements during impact. The acceleration in the impact direction (x-axis) for the trolley (Fig. 7), three dummy belt load sensors, two wheelchair rear anchorage load sensors (3-axis sensors) and two wheelchair front anchorage belt sensor, were used. The front belt consisted of two straps. A single sensor has been fitted on one strap only also the load exercised is multiplied by two. Measurements for the dummy (performance criteria as per Regulation 94 [9]) was composed with a three dimensional accelerometer for the head, the thorax and the pelvis. Also the

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Table 2 Test specifications. Test name

Wheel-chair

Test type

Securing wheelchair

Dummy

Deceleration corridor

Speed (km/h)

UFR101

A

Rigid platform

Static belt

Hybrid II

48+2 +0

UFR102

B

Rigid platform

Static belt

Hybrid III

UFR103

C

Rigid platform

Static belt

Hybrid III

UFR104

D

Rigid platform

Static belt

Hybrid III

UFR105 UFR106 UFR107 UFR108

D D D D

Rigid platform Body in white Body in white Body in white

Static belt Static belt Retractor belt Static belt

Hybrid III Hybrid III Hybrid III Hybrid III

UFR109

D

Body in white

Retractor belt

Hybrid III

UFR110

C

Body in white

Retractor belt

Hybrid III

UFR111

B front D rear

Body in white

Static belt Static belt

Two hybrid III

ISO 10 542 ISO 7176 ISO 10 542 ISO 7176 ISO 10 542 ISO 7176 ISO 10 542 ISO 7176 UN/ECE Regulation 80 UN/ECE Regulation 80 UN/ECE Regulation 80 ISO 10 542 ISO 7176 ISO 10 542 ISO 7176 ISO 10 542 ISO 7176 ISO 10 542 ISO 7176

thoracic deflection and the neck load were recorded (except test UFR101). 2.3.3. Dimensional measurements Trackers were placed to monitor specific points on the wheelchair and dummy and analyze the movement of these trackers over time during impact. Measurements are made before and after impact according to ISO Standards requirements.

48+2 +0 48+2 +0 48+2 +0 30+2 +0 30+2 +0 30+2 +0 48+2 +0 48+2 +0 48+2 +0 48+2 +0

2.3.4. Videos and photos A dedicated lighting system in the crash test area as well as high-speed cameras (up to 1000 frame per second) allow filming the tests. Three cameras were placed perpendicular in both sides and in oblique front view for all tests. For the second campaign one camera on oblique rear view and one in-vehicle camera in oblique front view were added. Also videos were shot at normal speed before, during and after impact. 3. Results 3.1. Impact characteristics The impact characteristics were shown in Table 3.

Fig. 6. Positioning of floor anchorage.

Fig. 7. Load sensors reference system at rear side.

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Table 3 Impact characteristics.

3.2. Loads exercised on the tiedown/restraint system

Test name

Speed (km/h)

Max. deceleration (g)

UFR101 UFR102 UFR103 UFR104 UFR105 UFR106 UFR107 UFR108 UFR109 UFR110 UFR111

48.60 48.50 47.95 48.50 30.60 32.71 32.76 48.09 48.35 48.56 49.60

21.0 22.0 21.8 23.2 11.0 11.3 11.7 21.7 21.2 20.0 20.5

The eleven-programmed decelerations were in the required corridor, except for the speed of UFR103 (47.95 instead of 48 km/h) and for tests from UFR108 to UFR111 (duration of deceleration of 20 g of approximately 7 instead of 15 ms as required). This was the maximum deceleration capacity of the bench stopping system.

The maximum loads exercised on floor anchorages associated to wheelchair tiedown straps are presented in the Table 4. Maximum loads add up WTORS. Loads on rear anchorages are expressed according to axes X forward, Y leftward, and Z upward (Fig. 7) and then the resultant force i.e. according to the direction of the belt. Loads on front anchorages are the measurements made on the belt. The loads at the rear anchorage are proportional to the wheelchair weight, to the deceleration low and to the angle of the anchoring strap. The rear anchorage loads reached 30 kN. In Table 4, missing values correspond to a technical problem of the front left retractor belt (UFR109) and at a failure of wires (UFR110). When the problem occurred, in the UFR109 test, it is at the end of the deceleration at the rebound phase. So the test is considered acceptable except for the load at the front left location. The angles values (Table 5) in side view are obtained by projecting the angle of each tiedown strap onto a vertical plane parallel to the wheelchair reference plane. The angle values did not vary too much before and after the impact.

Table 4 Floor anchorage load. Test name

Maximum anchorage load (kN) Rear right

UFR101 UFR102 UFR103 UFR104 UFR105 UFR106 UFR107 UFR108 UFR109 UFR110 UFR111

Rear left

In X

In Y

In Z

Resultant

In X

In Y

In Z

Resultant

11.45 14.31 20.29 23.78 10.59 11.53 12.63 20.31 21.30 26.31 10.65

1.13 0.11 0.06 1.23 0.83 0.75 0.64 1.15 1.88 1.13 1.42

9.63 10.99 10.91 18.42 9.48 9.77 9.37 15.65 15.31 13.55 7.85

14.99 17.95 22.99 30.10 14.14 15.11 15.74 25.66 26.21 29.60 13.25

8.88 10.94 17.97 22.69 9.29 10.94 11.54 19.77 19.64 26.02 10.23

0.52 0.10 0.13 1.80 0.66 1.08 0.71 1.68 2.43 0.89 0.85

5.43 6.83 7.92 15.93 7.60 8.27 7.97 13.53 12.24 10.73 5.61

10.41 12.93 19.65 27.78 11.95 13.74 13.99 24.01 23.19 28.13 11.69

Front right

Front left

5.42 5.58 6.46 9.20 2.98 9.02 10.14 8.36 8.22

1.94 1.80 1.00 7.36 4.04 6.88 10.44 10.02

6.86

0.20

Table 5 Angle of tiedown strap before and after impact. Test name

UFR101 UFR102 UFR103 UFR104 UFR105 UFR106 UFR107 UFR108 UFR109 UFR110 UFR111 a

Angle rear right in degree

Angle rear left in degree

Angle front right in degree

Angle front left in degree

Before impact

After impact

Before impact

After impact

Before impact

After impact

Before impact

After impact

30 29 20 45 48 45 46 49 48 33 35

25 30 20 47 45 43 51 50 53 28 40

24 29 20 45 47 44 45 48 47 30 35

27 27 20 47 46 42 48 43 62 27 40

28 23 20 42 40 41 48 44 50 26 30

30 22 20 41 40 43 45 43 39 15 20

26 25 20 41 41 43 49 42 49 28 30

27 20 22 41 41 41 46 43 Unavailablea 17 20

Technical problem with retractor belt.

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Table 6 Occupant belts load. Test name

UFR101 UFR102 UFR103 UFR104 UFR105 UFR106 UFR107 UFR108 UFR109 UFR110 UFR111

Max belt load (kN) Shoulder belt (left)

Pelvic belt at buckle side (right)

Pelvic belt at shoulder side (left)

12.48 13.12 9.83 11.63 5.78 6.38 6.24 9.07 9.32 7.06 10.94

12.44 13.94 12.78 13.31 6.98 7.83 7.56 11.62 11.89 11.42 11.54

7.38 12.78 8.40 8.56 3.76 5.78 5.06 8.24 8.82 8.08 8.02 Fig. 8. Standardized electric wheelchair after test (UFR 103).

The Table 6 illustrates the loads on the occupant’s belts. The loads reached, on the shoulder belt 13 kN, and on the pelvic belt 13 kN.

3.3. Features observed on the crash-test dummy The features observed on the dummy were compared with some of the limits required in Geneva Regulation 94 [9] for able-bodies occupant but which are not required in ISO 7176 [6] Standard (Part 19). For reasons of availability, leg sensors could not be used. Regulation 94 [9] criteria were complied with, except for the “neck bending moment” for test at 48 km/h (indicated in bold in Table 7). Nevertheless the neck bending moment for the dummy at rear position (UFR 111) is acceptable.

3.4. Filming-related data The films were tracked using Motion Track system, which allows measuring the movements of specific points materialized by trackers during the impact. The Table 8 presents the movements of the different points referenced in ISO 7176 [6] Standard (Part 19). The results obtained show that ISO 7176 [6] standard requirements were complied with, except (indicated in bold in Table 8) for head backward movement during UFR103 and UFR110 test (backrest distortion). The dummy’s movement in comparison with the space allocated to the WCU are also analysed. The knee forward movement does not exceed the WCU space in length (1300 mm). On the other hand, a vertical head movement of 100 mm above its initial position should be noted. Lastly, a significant movement of the legs, forward (200 mm) and upward (1000 mm), should be noted.

Table 7 Features on crash test dummy. Biomechanics criteria Test name

UFR101 UFR102 UFR103 UFR104 UFR105 UFR106 UFR107 UFR108 UFR109 UFR110 UFR111 front UFR111 rear Limit value regul 94

Head: max 3 ms (g)

67 50 45 47 19 21 37 48 70 67 53 41 < 80

Criteria was exceeded in bold.

Neck: max load (kN)

Neck: max bending moment (Nm)

Tension

Shearing

Extension

1.79 1.40 1.52 0.59 0.73 1.26 1.30 2.54 2.33 1.54 1.48 Corridor

1.42 1.41 1.39 0.64 0.12 0.35 0.46 0.60 0.44 0.54 1.07 Corridor

85 87 75 42 35 55 71 82 107 63 54 < 57

Thorax: max 3 ms (g)

Thorax: deflection (mm)

Pelvis: max 3 ms (g)

40 38 43 20 26 21 40 40 34 30 34 < 60

38 29 26 13 20 18 22 29 15 34 Unavailable < 50

45 47 41 49 22 30 25 57 59 42 37 59 No

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Table 8 Horizontal excursions of the dummy and the wheelchair. Horizontal excursions Test name

Head (forward) mm

Heada (backward) mm

Wheelchair point Pb (forward) mm

Knee (forward) mm

Knee versus wheelchair (forward) %

UFR101 UFR102 UFR103 UFR104 UFR105 UFR106 UFR107 UFR108 UFR109 UFR110 UFR111 Limit ISO 7176

367 287 275 219 171 242 405 333 420 490 280 < 650

178a 330a 681a 306a 119a 219 332 257 374a 507a 228a < 400

2 1 18 114 68 66 134 83 88 134 107 < 200

190 219 160 189 90 171 171 221 214 193 108 < 375

9400 21800 780 65 32 157 28 166 213 15 18 > 10

Excursion was exceeded in bold. a The backward movement of the head could not be measured until the end: either the tracker was no longer visible or the head bumped onto the shoulder strap anchorage. b Point P is a wheelchair point defined in ISO 7176 Standard (Part 19), situated close to the dummy’s hip. The rear wheel axis was used when point P was not visible.

Photographs after impact (Figs. 8 and 9) are presented as a reminder. 4. Discussion This paper checked the protection offered to the WCU by using wheelchair and WTORS conform to the current standards. To identify possible failures a series of crash tests, on a rigid platform and in BIW was carried out. It should be reminded that the highest performance equipment was used during the tests campaign. The ISO 10542 Standard restraint system (straps) proved satisfactory during the eleven tests. Releasing the strap was easy; and dummy restraint and wheelchair tiedown worked well. The restraint system was sometimes damaged but complied with the ISO 7176 [6] Standard requirements.

Fig. 9. Standardized manual wheelchair and surrogate wheelchair after test (UFR 111).

Implementation was trouble-free except for the accurate identification of anchorage points on the wheelchair. The fact remains that the installation may seem long for frequent use for moderately informed person. As illustrated in the Table 5, the loads on the floor and, therefore, by reaction on the wheelchair are highly dependent on the angle of the anchoring strap in relation to the horizontal axis (from 20 to 45◦ ). Angle reduction results in the smaller value of the vertical component, which crashes the wheelchair to the floor and proves highly destructive. In addition, rear floor anchorage, opposite the shoulder strap, is always overloaded than the other rear floor anchorage. The manual wheelchair has angle (rear securement point on wheelchair) conform with the ISO 10542 [5] requirements. Also, the electric wheelchair has angle smaller (rear securement point on wheelchair lower) and the SWC has angle higher (rear securement point on wheelchair higher) than ISO 10542 [5] requirements. The rear anchorage loads reached 30 kN. These results obtained have shown a comparable order of magnitude in the literature (Le Claire et al. [4]). The load on shoulder belt, reached 13 kN, are greater than shown in the literature (Le Claire et al. [4]), 10 kN. Regarding the pelvic belt, the results obtained up to 13 kN, are quite lower than in the literature (Le Claire et al [4]), 30 kN. Our results were on rigid platform and in BIW. In literature no results on loads in BIW are yet available. The non-standardized wheelchair’s behaviour was not too bad given the freedom that the user had to choose the anchoring point. It was randomly positioned as low as possible, which proved to be a rather favourable option given the results obtained. The left-hand side elbow rest was ejected though. The overall integrity of the non-standardized manual wheelchair is coincidental considering that the selection of anchorage points is free and may therefore be implemented in the wrong manner or entail

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fully different loads (Fig. 3). This can be observed through the influence of the traction angle of the wheelchair tiedown strap upon the loads generated on the floor. The left front wheel of the manual standardized wheelchair was broken, the footrest was broken and the headrest ejected. Ejection of an object could cause injuries for the WCU and for the other occupant. The backrest of the electric wheelchair was warped. The problem of backrest distortion causes too great a head backward movement. The behaviour of these wheelchairs is borderline in comparison to the ISO 7176 [6] requirements. It should be noted for the SWC, that both the backrest and footrest remained intact; however, this wheelchair is specifically used for crash-tests and therefore not intended for daily use. Concerning the head, there should be some space for the restraint offset or functioning of at least 100 mm in relation to the height before impact. In all tests the dummy’s leg movement was significant, but leg movement is not taken into account in the requirements. That should be taken into account soon. There is little difference in behavior between retractor belt systems or static belt systems. It appears that the wheelchair moves less with the fixed system. Regarding biomechanical criteria, the “neck bending moment” criterion was exceeded in all tests at 48 km/h (except UFR 111, for the front dummy, but the front left wheel was broken). The tests carried out at INSIA in Spain (Senin et al. [3]) gave evidence of the same over-range. The issue now is the room required for WCU in the space offering restraint systems, considering that the size of wheelchairs increases over time. What we mean here is the space needed for the satisfactory safety of the user and not the space required for accessibility. Currently, this space is 1300 mm long, 750 mm wide and 1350 mm high, based on the dimensions indicated in Directive 2001/85/EC (buses). The test performed showed no knee movement further than the length provided (1300 mm), this result has to be taken carefully because the knee target was sometimes hidden by the pillar at the maximum of the displacement. However, it seems to us that the height (1350 mm) is a little insufficient considering head movements. The maximum height from the floor (above the head of the dummy sat in the wheelchair), measured with the four wheelchairs used with a 50th percentile dummy (1.75 m), is 1450 mm at most, to which should be added the head upward movement in case of impact i.e. 100 mm and a vertical clearance of 100 mm. Therefore, the space provided should have a total height of 1650 mm. Some European countries go as far as 1 800 mm in height so that the person assisting (attendant) a WCU can stand next to them during lift operation. A forward and rearward clear zone should be provided so as to reduce potential for head impact with the vehicle interior in a crash. The clear zone should be approximately 0.4 m behind the wheelchair-seated occupant’s head and roughly 0.95 m in front of the occupant’s head, as proposed by Wretstrand et al. [11]. This zone should be provided through the full height to

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the occupant’s head, and should be the width of the securement station. The test carried out with the two dummies went well. The BIW, fitted with reinforcement pieces for floor and belt anchorages, resisted well too. In addition, there was no interaction between the two occupants. The specificity of this testing campaign is test UFR 111, which included two wheelchairs and two dummies in the same vehicle. According to the current literature, this has never been carried out before. 5. Conclusions The ISO 10542 WTORS proved satisfactory during the tests performed. A few damages, but not breakage, were observed. The behaviour of both standardized wheelchairs, as per ISO 7176 [6] Standard (wheelchairs) was satisfactory or acceptable. The implementation of Directive 2007/46/EC requirements to accessible buses offers much greater safety to WCU, which allows passing from a degree of safety during braking to safety against impact. However for LV, the impact conditions described only relate to frontal impacts while it should be noted that the safety of able-bodied occupant is needed for side and real impacts. Impact standardization of wheelchairs is required with a view to achieving, beyond satisfactory resistance, a universal anchorage system i.e. a system for tying down the wheelchair to the vehicle. This standard will further enable to clearly identify tiedown points on the wheelchair and on the floor. Conflicts of interest statement No conflict of interest. Acknowledgements Authors wish to thanks P. Joffrin, A. Maupas, G. Goutelle, S. Serindat, J. Russo, J. Lardière, A. Gilibert. The authors gratefully acknowledge the kind review and suggestions of D. Mitton. INRETS was granted by the French DGMT (General Directorate for Sea and Transportation). These tests were carried out from our request by the UNEX safety test Unit. References [1] Schneider LW, Klinich DK, Moore JL, MacWilliams JB. Using In depth investigations to identify transportation safety issues for wheelchairseated occupants of motor vehicles. Medical Engineering and Physics 2010;32(3):237–47. [2] Shaw G. Investigation of large transit vehicle accidents and establishing appropriate protection for wheelchair riders. Journal of Rehabilitation Research and Development 2008;45(1):85–108. [3] Senin AR, Saez LM, Corral TV. Experimental evaluation of the wheelchair occupant protection under different impact conditions using commercial wheelchairs. International journal of crashworthiness 2006;11(5):425–41. [4] Le Claire M, Visvikis C, Oakley C, Savill T, Edwards M, Cakebread R. The safety of wheelchair occupants in road passenger vehicles. Wokingham: TRL; 2003.

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[5] ISO 10542. Technical system aids for disabled or handicapped persons. Wheelchair tiedown and occupant restraints systems. Part 1. Requirements and test methods for all systems. Part 2. Four point strap-type tiedown and systems. 2004. [6] ISO 7176. Part 19 Wheelchairs: wheeled mobility devices for use in motor vehicles 2008. [7] Kim SM, Yang IC, Park SY, Lee MP. Evaluation of wheelchair occupant safety in frontal and side impact of wheelchair loaded vehicle by computer simulation analysis method (Adams + Lifemod). Journal of Biomechanics 2006;39(Suppl 1):S536.

[8] Fuhrman S, Karg P, Bertocci G. Characterization of pediatric wheelchair kinematics and wheelchair tiedown and occupant restraint system loading during rear impact. Medical Engineering and Physics 2010;32(3):280–6. [9] UN/ECE Regulation 94. Uniform provisions concerning the approval of vehicles with regard to the protection of the occupants in the event of a frontal collision 1995. [10] UN/ECE Regulation 80. Seats of large passenger vehicles 2003. [11] Wretstrand A, Bylund P, Petzall J, Falkmer T. Injuries in special transport services – situations and risk levels involving wheelchair users. Medical Engineering and Physics 2010;32(3):248–53.