Heavy goods vehicles
Impact of different payload on crashworthiness of safety barriers
In TRANSFORMERS, a recent co-funded EU project in the Seventh Framework Program, different configurable and adaptable trucks and trailers were developed for optimal transport efficiency. Further information is available at: www.transformers-project.eu.
For an aimed CO2-reduction of 25% aerodynamic measures and new technologies have been implemented in two prototypes of trailers:
- Energy Efficiency Trailer: “Hybrid on demand” concept with electric driveline (41 t).
- Load Efficiency Trailer: Adaptable cargo optimization with a second cargo floor (40 t).
In most European countries the maximum permissible weight for heavy goods vehicles is 40 t (exemption for combined transport: 44 t). An extra one ton for alternative powertrain can be used in the electric hybrid-on-demand frame according to paragraph (6) and (7) of Directive 2015/719/EC.
These new vehicle configurations might have an influence on infrastructure and needed to be analyzed with regards to their impact on the road and the road equipment. For traffic safety reasons the mechanical impact on different types of safety barriers have been assessed using numerical simulations (instead of cost- and time-expensive crash tests).
For the simulation activities Finite-Element models of a concrete wall and a steel guardrail with a containment level of H4b were developed. H4b safety barriers traded in Europe have to pass a crash test with a truck according to the European harmonized standard EN 1317. The test setup requires a vehicle weight of 38 t, an impact velocity of 65 km/h and an impact angle of 20°.
In a first step and for validation reasons a vehicle configuration with 38 t was calculated and compared to real crash tests according to EN 1317. Based on this crash scenario following vehicle configurations were investigated.
Case 1 (41 t): Additional masses for the electric driveline components
Case 2 (40 t): Additional masses for aerodynamic measures and a second cargo floor
Investigations showed that the selected H4b safety barriers with the highest containment level available on the market are just able to contain common heavy goods vehicles with different distributions of payload not least because of their double-row installation in the median of highways.
However high centers of gravity of the payload have been identified as a critical issue with regard to the risk of rollover in crashes with safety barriers. Features such as the hybrid driveline concept developed in TRANSFORMERS instead tend to lower the center of gravity, thus improving crash behaviour.
If the trend towards heavier optimally loaded vehicles (case 2) continues and the percentage share of those vehicles exceeds a certain limit and/or higher speed limits for HGV are requested in the future, additional requirements for payload positions will be highly recommended in a further amendment of Directive 2015/719/EC. Alternatively or in addition a potential amendment of EN 1317 might improve the crashworthiness of safety barriers by introducing other vehicle configurations and/or other containment levels.