Innovation in wheelchair tiedown and occupant restraint systems

Abstract

In general, for transportation of wheelchairs by taxi buses, so called ‘four-point strap-type tiedown systems’ are used for securing wheelchairs. At four points around the wheelchair self-retracting straps are connected to the vehicle floor. These straps are equipped with hooks which can be attached to various points of the basic geometry of the wheelchair. After attachment the straps are tightened. In 2006, LOCOmotion carried out a research in commission of Sociaal Fonds Taxi on the physical workload for taxi drivers for four different restraint systems, including two variants of the four-point-system. It was found that the driver needs to work in positions that are physically stressful for a large part of the time. For all four restraint systems, frequent bending and kneeling is necessary. In long term this will bring health risks. The goal of this project is to do research on the current wheelchair transportation system and develop a wheelchair tiedown and occupant restraint system that improves the usability and working conditions and reduces the physical workload for the taxi driver. Wheelchair transportation can be considered as a system that consists of three main components; the vehicle, the wheelchair and the securement system. In this system, the securement system functions as the link between the vehicle and the wheelchair; it has to connect these two components to each other. The main problem is that there is still no standard attachment point on wheelchairs, like a towing hook on cars. With the consequence that the securement system needs to be very flexible in order to adapt to the large variation in wheelchair types and brands. A central question in the analysis phase was: How to design a securement system that fits to as many different wheelchair types as possible on the one side, and depends as less as possible on standardization on the other side? From the analysis was found that if new standard attachment points are going to be developed, they need to be detachable, discreet and lightweight. Wheelchair geometry from different kinds of wheelchairs was analyzed and it was found that the frame areas near the suspension of the rear wheels offer the best possibilities for attachment points. A range of height and width in which the adapter could be placed is also necessary, because the variation in wheelchair sizes and construction is too large. By means of user observation was concluded that it is desired to secure the wheelchair from a standing position as much as possible and that manoeuvres around the wheelchair should be reduced as much as possible. In the development of a new securement system a gradual market introduction was taken as a starting point. This implies that the new system will be used next to the current four-point strap-type tiedown system. The attachment points on the wheelchair and the vehicle need to be suited for both the old and new system. Five development directions were formulated ranging from short term solutions like optimizing the four-point strap-type system, to long term solutions like an automated system integrated into the vehicle floor. A combination of two directions was chosen: adapters on the wheelchair that provide the flexibility instead of the securement system and securement from the rear side. Three diverse concepts were developed. The concept that consisted of the idea to pin the wheelchair to the ground with two sticks was preferred and has been further developed. The result is a securement system that consists of two separate clamp units that can be clicked onto the wheelchair from the rear side from a standing posture. The clamp units fit into a crosswise airline track that should be installed into the vehicle floor. A lever on each clamp unit can be pulled to secure everything at once. A three point occupant restraint is also incorporated into the design. The final design proposal has been evaluated on different aspects. A strength analysis was performed to evaluate the construction and a functional prototype was built to test the clamping mechanism and the usability of the system. Considering the system was developed from scratch in only five months time, many aspects for further development were found. The usability can be further improved by making actions such as securing the clamps or detaching the clamps easier. The construction should be more robust to make it better resistant to rough usage and stronger to make it better resistant to impact loadings. It should be noted that extensive testing, by means of crash-tests, will be required in order to make judgments about safety with certainty. Nonetheless it was demonstrated that the clamping mechanism is a feasible solution. The comparison to the four-point strap-type tiedown system showed significant reduction of physical workload and application time. The report concludes with different scenarios for future development. This project illustrates a scenario where each stakeholder is only required to take a small step towards a certain degree of standardization. Wheelchair manufacturers should take small and lightweight adapters into account in their development. An additional advantage is that the adapter can be positioned at any height or width. The car conversion companies should apply crosswise airline tracks in the bus interiors. A separate ramp containing crosswise tracks could be retrofitted to existing buses. Crosswise tracks could also be combined with existing floor integrated systems. Other scenarios will illustrate that if stakeholders are willing to apply a higher degree of standardization, the usability of wheelchair securement systems and the working conditions for taxi drivers could be improved even more.