Francisco Castro

This paper presents a practical and cost-effective method for in-motion estimation of a vehicle’s CoG position in all three directions by measuring accelerations during two types of maneuvers: braking (longitudinal and vertical CoG estimation) and cornering (lateral and vertical CoG estimation). The proposed method’s main advantage is that it does not require knowledge of vehicle characteristics, such as mass distribution, suspension geometry, or inertia parameters. It relies solely on the known distances between the sensors and their positions relative to a defined reference point on the vehicle. To validate the developed method, experimental tests were conducted on a prototype vehicle, varying the load conditions for the proposed driving scenarios. The CoG position obtained from dynamic maneuvers was compared with reference values derived from static measurements. The results showed that the proposed method could estimate the CoG position with an average error of 3% in the longitudinal direction, a maximum error of 12% in the lateral direction, and a maximum error of 14% in the vertical direction.

This paper analyzes the dynamic behavior of a passenger bus running on a raised crosswalk. The main objective was to evaluate the vertical displacements and accelerations caused by the change in elevation, and to determine the potential for suspension damage. The study involved a numerical approach to the examination of a vehicle’s displacement related to the profile pavement by the implementation of a single body finite element module with suspension subjected to the effect of road unevenness. The so-obtained dynamic behavior with this model was implemented in MATLAB software, and the results were compared with the corresponding real-world accident data record and with an experimental study carried out with a bus running on a raised crosswalk at prescribed velocities. The velocity on the day of the accident was then calculated by computational simulations using the software PC-Crash^®. The results show that the vertical displacement caused by the raised crosswalk can vary according to the bus velocity and the raised crosswalk height. Moreover, the results show that reducing the height of the raised crosswalk and redesigning it for a smoother transition with the pavement can help in minimizing the negative effects from impacts on the bus body. The findings of this study provide valuable insights for engineers and transportation planners, and can be used to improve the design and placement of raised crosswalks in the future.

Road accidents cause 1.3 million deaths annually, motivating the United Nations (UN) to develop a strategy seeking to halve this number by 2030. Portugal, with 60 deaths per million inhabitants in 2022, ranks sixth in European Union (EU) road fatalities, although these numbers have been decreasing since 2010. Rollover accidents account for 33% of traffic fatalities in the U.S.; yet, only 3% of crashes involve rollover accidents. These are particularly dangerous and mainly involve medium-to-large-sized vehicles having high centers of gravity (CoG), such as SUVs and heavy vehicles. On the other hand, bus accidents make up only 2% of EU road deaths, often involving vulnerable road users. Road forensic investigations rely on CoG positioning data for accurate accident reconstructions, using key equations for calculating skid and overturning speed limits. To complement the already existing equations, and by using a rigid body system, an equation for the evaluation of the overturning velocity in a curved trajectory is developed and proposed, considering the suspension stiffness properties of a vehicle. Finally, a real-world accident investigation involving a bus overturning is presented, and the method that was developed is applied. The developed formulation showed good results compared to the ones that were obtained during the forensic investigation and reduced the error from 5% to 2% compared to the existing equations.