Tests of lateral acceleration during a controlled skid - various types of vehicles

This article presents the values of lateral acceleration during controlled slip for a passenger vehicle and a city bus. Skidding is one of the most dangerous road situations that can occur while driving a vehicle. They can happen to anyone, without exception whether someone has experience or is a young driver. The lateral accelerations during the controlled skidding presented in the article showed higher values for a passenger vehicle. The article refers to drawing attention to the lateral accelerations acting on the vehicle during the slip. It depends on the driving system of the driver whether he will be able to make the correct choice in a dangerous situation. Therefore, improving driving techniques, especially in a skidding situation, should be generally available to drivers.


Introduction
One of the scariest things that can happen while driving is losing control of your vehicle due to skidding. Skidding is the result of a loss of grip between the vehicle tires and the road surface [1][2][3][4]. This is usually because the driver accelerates too rapidly, brakes too hard, changes direction abruptly at too high a speed. Front wheel skid occurs when a vehicle's front wheels lose traction. Front-wheel drive vehicles (front-wheel drive) suffer from this problem more often than rear-wheel drive vehicle [5][6][7][8]. This is mainly due to the fact that the front wheels drive the vehicle and require more grip than the rear tires [6][7]. Front wheel slippage usually occurs when braking hard, when the front wheels lock up, or when trying to corner too fast for road conditions. Front wheel skid is also known as understeer because the vehicle is going straight no matter how much pressure on the steering wheel [9][10][11]. Rear wheel skid occurs when the rear wheels lose traction. It happens either during heavy braking, especially in the case of failure of the rear brakes, or more frequently, when the corner is taken too quickly [10][11]. In this respect, vehicles with rear wheels suffer more often from slippage of the rear wheels than vehicles with front-wheel drive because the rear wheels drive the vehicle and thus place additional demands on the tires [12][13].
It should be noted that one of the main causes of vehicles accidents is the speed not being adjusted to the road conditions [14][15][16]. This means that slippery ground or poor visibility is a serious hazard. Experts argue that sharp turning of the steering wheel will be useless if we skid while driving or we have to avoid an obstacle, eg a pedestrian who suddenly appeared on the road [16][17][18][19].

Research methodology
The research was carried out on the training and training track located 20 km south of Radom in the Jastrząb commune. The research used a skid-in-run plate (100x20m), equipped with a dynamic plate of the "jerking devices" type. The plate allows the vehicle to skid at speeds above 40 km/h. Figure 1 shows IOP Publishing doi:10.1088/1757-899X/1247/1/012015 2 a skid-and-overrun plate with a dynamic plate of the shredder type. When the rear axle of the vehicle travel the plate of the controlled skid station, the hydraulic vehicle axle jerking device will dynamically move the entire plate of the device in the transverse direction to the specified direction of travel. The surface of the plate with a high coefficient of adhesion causes the rear axle of the vehicle to deviate from its previous direction of travel, simultaneously causing it to skid. After reaching the extreme position, the device quickly returns to its initial position. In order to reduce the adhesion of the vehicle to the surface, the skid-run plate was covered with a layer of water throughout the entire duration of the tests. The initial speed of the vehicle, for which the horizontal acceleration values were determined, was 40 km/h and 50 km/h. The tests were carried out at an ambient temperature of about 20°C. During a series of tests, the dynamic plate was set to random mode, thanks to which the driver approaching the plate was not able to predict which side the plate would be dislocated. An Audi A6 passenger vehicle and a city bus were used in the research. Each time, a series of 5 measurements was performed. During the tests, the vehicles were loaded with the driver, measuring equipment (about 20 kg) and the person carrying out the measurement. To register the traffic parameters of the tested vehicles, specialized measuring equipment was used, including: • TAA Datron® triaxial linear acceleration sensor and TANS Datron® linear and angular acceleration • uEEP-12 Datron® data acquisition stations with ARMS® data analysis software, • S-350 Aqua Datron® optoelectronic sensor for measuring longitudinal speeds.
The first vehicle to be tested was the Audi A6 passenger vehicle. Its curb mass was 1,920 kg (permissible mass 2,475 kg). The vehicle is equipped with a power unit with a capacity of 2,967 cm 3 and a power of 176 kW. The second research vehicle was a city bus capable of carrying 54 passengers. During the controlled skidding, the vehicles accelerated to the assumed speed, and then ran onto a dynamic plate. Depending on the position of the plate, the rear axle of the vehicle moved to the left or right side. The driver's task was to get the vehicle out of a controlled skid, while keeping the vehicle on a skid plate. Figure 2 shows a city bus during a controlled skid test. On the other hand, in Figure 3 of the Audi A6 passenger vehicles, during a controlled skid test.

Conclusions
Staying alert while driving is critical because being aware of a problem and resolving it in seconds can mean the difference between causing an accident and solving the situation safely. Slippage cannot always be avoided. Every skid is different and involves many factors related to driver activities, road conditions and hazards. The research showed that the Audi A6 passenger vehicle had a much shorter duration of controlled skidding than in the case of the city bus. Skidding can happen to anyone, and the more someone drives, the more likely it is. For our own safety, we should be able to deal with such unexpected behavior of the vehicle, preferably under control conditions. Improving the driving techniques of the driver contributes to increasing the safety of the driver and other road users.