Truck emergency braking and role of load restraining in road transport safety

Studies on road transport safety in France, carried out by INRS (French National Research and Safety Institute) and the LMA (Laboratory of Accident Mechanisms analysis) of the Gustave Eiffel University, identified the circumstances and severity of heavy goods vehicles accidents when the causes were related to load restraining. A recent survey made by the LMA in 2022 using 1/50th of the police report data showed that 16 accidents with victims per year, involving a heavy truck, could be related to a lack of load securing. A previous study carried out by the INRS had also estimated that 50,000 spills or releases of goods arise onto the road. The police control carried out on heavy goods vehicles showed that the load restraining rules, given in the standard NF EN 12195-1, is rarely conformed. This work focuses on establishing the technical elements and knowledge that will allow the creation of prevention materials in term of load restraining by realizing experimental tests reproducing the loss of a load due to an improper load restraining. Emergency braking tests were performed at 80 km/h on a Renault Premium 270 truck carrying two loads of 1600 kg (barrels filled with sand). The loads are secured using top-over lashing method. The first load is secured according to the dimensioning rules of the European standard (NF EN 12195-1). The second load is secured in a rudimentary but realistic way regarding to the work habits of some operators. The truck is instrumented with a 10 Hz frequency GPS positioned in the driver cabin in order to measure an accurate speed. Android Smartphones are also used as data acquisition systems through an application developed by the LMA, to measure the accelerations and rotation velocities along three axes. Four smartphones installed on front and rear parts on the flatbed truck and on the 2 loads were used to measure the dynamics of the truck and of the loads during the tests. Fourteen telemeters were installed around the loads to measure their displacement. Tension forces in the straps are measured by load sensors. Tests were filmed by two drones and four cameras installed on the truck to see the loads movement. Measured braking decelerations for the first and the second tests are 4 and 6 m/s respectively. For the first test, loads remain stable during braking. For the second test, the rudimentary secured load slides and hits the cabin protection made of old tires, while the second load stays in place. The measured deceleration of the rudimentary secured load is lower than the truck s one because of the sliding, lasting one second before hitting the cabin protection. The relative velocity between the load and the truck is around 3 km/h, however the generated impact force is 25 kN. This study highlighted the importance of the load securing in road transport. More critical situations such as lateral acceleration in turns will be tested for a better understanding of influence of the load lashing quality on transport safety.