Currently, no passive safety regulatory requirements for passengers of urban buses exist, mainly based on its low operational speed. Nevertheless, crash reports at the city of Madrid show that even fatalities can occur amongst urban buses passengers.
The objective of this research is to assess the level of protection achieved on seated passengers on the current Madrid urban buses seats. Also, secondary aims are considered:
- Obtain a representative configuration of urban buses collision (acceleration pulse).
- Assess the seats’ resistance (are seats able to withstand crash loads?).
- Evaluate the seats’ restraint (compartmentalization).
To obtain a representative deceleration pulse for urban bus collisions, FE models have been used. The FE models validation process includes a sled crash with a mobile deformation barrier (EuroNCAP AE-MDB version), acting as bullet vehicle, and the frontal part of an urban bus (supported by load cells and including strain gauges for obtaining loads in five axis in three beams of the bus structure). To analyse occupant safety, sled tests were performed with the acceleration pulse obtained. Adult (Hybrid III 50 th & 95 th male) and child impact dummies (Q1.5, Q3 & Q6) were used. The Hybrid III 50 th includes instrumentation at head, upper neck, chest, femurs, knees and tibias. Whereas Q-dummies at head, upper and lower neck, chest and pelvis.
A reliable crash pulse for urban buses was obtained for a better estimation of the protection requirements that urban buses could need in the future. Currently there are safety requirements for long distance buses (UNECE R80) with accelerations of 6.5-8.5 g and a delta-v of 30-32 kph. Nevertheless, the R80 crash severity has a higher severity than urban bus collisions.
The kinematics and the injury criteria obtained from the dummy readings are used to evaluate the protection capabilities of each tested configuration. Also, comparison of the dummy signals allows making recommendations.
The acceleration pulse representative of urban bus collisions has been developed using FE models. Based on the simulation results, it was taken the most severe acceleration pulse of the plausible configurations simulated. That configuration corresponds to the frontal collision (100% overlap) of an urban bus (12 t) at 50 kph impacting against a vehicle (2 t) at 50 kph. This configuration represents the invasion of the opposite lane of one vehicle when both vehicles are travelling at the maximum road speed.
The occupant analysis was performed using only one type/model of urban bus seat. There are configurations which were not tested such as bay seating, seats placed at different height or standing passengers. To conclude, the acceleration pulse of a representative urban bus collision has been developed. The urban bus seats are able to withstand the crash load; the structural strength has been assessed with 95 th mass dummies. The worst configuration for adult occupants has taken place in rearward projection due to the neck injuries. A large extension (moment and angle) has been observed.
The compartmentalization for child occupants has been deficient; dummies finish the test on the floor. For child dummies, the safest configuration is when they travel in rearward facing seats.