Abstract
Keywords: seats, rollover's requirements, coaches, passive safety, restrain systems.
The introduction of safety belts in the passengers' seats of coaches could have important repercussions increasing their safety under frontal impact and rollover.
This type of vehicles has a particularity from cars or trucks: the safety belts are fixed directly to the seats and not to the vehicle structures. So on, to guarantee the correct retention of the passengers, the fixation of the seat to the vehicle must be verified. Nowadays regulatory prescriptions under frontal impact must be surpassed.
In case of rollover, the belted passengers increase the energy that must be absorbed by the superstructure because some of their mass must be considered us rigidly joined to the vehicle. This situation has been taking into account in the current European legislation, inside the last revision of the Regulation UN-ECE 66, which is going to be mandatory for new types from October 2010. A considerable number of coaches' manufactures are modifying their structures under this new revision because they take in mind that if the safety belts are yet included in the coaches, the superstructure must be in accordance. This is an important effort of redesign: more resistant structures but without weight increase (1).
So, we have mandatory requirements for the seats and restrain systems under frontal impact and for the structure under rollover... But nowadays there is nothing in regulation about the seats, their anchorages or the safety belts' anchorages to assure a correct passengers' retention under rollover.
The lateral strength of seats must be analyzed and we think it could be done under two points of view:
- To obtain the behaviour to determine if they are correct restraint systems for the occupant in case of rollover, maintaining the seats fixed to the vehicle.
- As a component to be taken into account in the energy absorption capability of the whole superstructure in case of rollover.
This paper presents the first part of the research carried out by INSIA-UPM to analyze this item. First of all, the mechanism of deformation of these components under rollover has been defined, analyzing the loads that could be transmitted to the seats. From this analysis, a characterization test has been defined and the devices manufactured and tested on some current coaches' seats. Finally some conclusions are presented about the necessity of possible new requirements to guarantee the correct retention of the coaches' occupants in a rollover accident and how seats could help in the structural absorption capabilities of the coaches in case of rollover.