# Study of Loads Acting on the Load during the Sudden Braking of a Vehicle
## 1 Introduction
The possibility of monitoring accelerations and the related forces acting on cargo was also analysed by [PERSON] et al. They carried out measurements in several selected points of the box body of a loaded vehicle [22]. The authors believed that the monitoring of accelerations recorded in several points allowed them to identify areas with a higher risk of cargo damage within a vehicle's box body. This information can be used to adapt the packaging and secure the cargo appropriately or to modify the transport route. The selection of elements preventing the cargo from moving requires the knowledge of forces acting on this cargo during transport. Loads that act on cargo during transport are generated mainly by inertial forces connected with the movement of the vehicle, its vibrations, or tilting. They can act in the longitudinal, transverse, or vertical direction. Longitudinal inertial forces occur during the acceleration or braking of the vehicle and transverse forces occur during curved motion, whereas any road surface irregularities generate vertical forces. According to standard EN 12195-1, the maximum values of longitudinal forces that must be considered for the selection of fastening elements constitute the mass force of the cargo (Q\({}_{\rm l}\)) expressed by the coefficient C\({}_{\rm x}\), which, according to the standard, equals 0.8 (Figure 1) [5; 6; 7; 8; 9]. \[{\rm C_{x}=\frac{a_{x}}{g}} \tag{1}\]  
where g--acceleration of gravity 9.81 m/s\({}^{2}\). In accordance with equation No. 1, the value of coefficient \(\rm C_{x}\) depends on the value of the acceleration of the mass centre of the transported cargo. The maximum value of the acceleration of the centre of mass (\(\rm a_{x}\)) is equal to the deceleration of braking (\(\rm a_{H}\)). The value of deceleration is influenced by the adhesion of the wheels to the road surface, the mass of the vehicle, the mass distribution of the load being carried [23; 24; 25; 26], and the design of the braking system [27; 28; 29; 30]. A high value of braking deceleration and simultaneous inertia forces acting on the vehicle and load can also be the result of poor driving technique on the part of the driver. The characteristics of such a driving technique are rapid braking, rapid acceleration, and excessive speed on a curve of the road [31; 32]. The emergency braking process for trucks and commercial vehicles has been studied by [23; 24; 25; 33]. A study and analysis of the emergency braking of an N3 category vehicle carrying loose cargo was presented in the article [23]. In none of the described tests, the deceleration value of the vehicle did not exceed 0.8 g during intensive braking. [PERSON] et al. [24; 25] studied the effect of the position of the cargo's centre of mass on the value of deceleration achieved by N1 and N2 category vehicles. They showed that lowering the centre of mass and bringing the centre of mass closer to the rear axle of a vehicle of the N1 and N2 categories increased the value of deceleration and, at the same time, shortened the braking distance. In four of the sixteen post-measurement tests of sudden braking performed, the value of longitudinal deceleration exceeded 8 m/s\({}^{2}\). There are no articles in the available literature describing the results of studies on the influence of driving technique and vehicle category on the choice of cargo securing. The lack of such publications, as well as some inadequacies of the European standard EN 12195-1:2010, which omits vans, inspired a series of studies covering the emergency braking of trucks and commercial vehicles. The aim of these tests was to verify whether the value of standardized coefficient \(\rm C_{x}\), which, according to the existing standard, equals 0.8, should be corrected depending on the type of transporting vehicle or the technical condition of the road surface. This article describes the object and conditions of the tests and presents the results of braking deceleration of a truck and commercial vehicles.