Abstract
The most frequent accident type of buses, the frontal collisions have a very wide range of varieties. On the other hand a lot of different goals are belonging to this subject: protection of the bus passengers, protection of the driver and the crew, the outside partners in the accident, the control systems of the bus, etc. It means that this problem is very complex. The international regulatory work is not so strong on this field, there is only one UN-ECE safety regulation (R.80) dealing with the required strength of bus seats and seat anchorages. In the frame of the UN-ECE organization (WP.29 / GRSG) more attempts tried to step forward, but without reasonable results. (The author participated in these efforts). This paper uses a complex approach to the solution with the help of statistics, structural analysis, energy consideration, etc. Based on accident statistics and accident analysis containing more than 400 events, the paper classifies the basic accident situations to be considered, the different goals mentioned above and specifies the so called “standard accident situations” from which the different requirements and approval test methods can be derived. Different criteria shall be applied in different safety regulations: energy criterion, deformation criterion, survival space requirement, functionality, etc. this is discussed in the paper. It is proved that the above mentioned goals cannot be solved in one international safety regulation, a set of regulations are needed. The structural analysis of the superstructure of the front part of buses – front wall structure, driver’s cab, bumper, main longitudinal underframe elements, etc. – can be elements which can absorb considerable amount of energy, which can provide the required strength and also which are dangerous in respect of the survival space in frontal collision.
The conclusion of the paper is that at least one safety regulation is needed to solve the driver (and crew) protection, and two more, one for the passengers protection assuring the described deceleration pulse and one against underrun of cars and for the protection of sensitive control systems (brake, steering, electric, etc.)
The paper cannot solve the whole, complex problem, but tries to give a logical frame for the future works and investigations to produce the missing international safety regulation for driver protection.
Keywords: Bus, frontal impact, safety, regulation