A Research on the Effect of Velocity and Road Type on the Ride Smoothness of 16-Seat Passenger Buses Using a Mechanical Suspension System

The vibration of cars and 16-seat passenger buses is affected by operating conditions such as velocity and road type. While in motion, the road surface creates vibrations that affect the vehicle and its passengers. Vibration acceleration, the maximum vertical acceleration of the vehicle body (amax), is used to evaluate smoothness and the impact of vibration on passengers. To establish a basis for evaluating smoothness and determining the limit velocity on different types of roads, this article built and investigated a spatial dynamics model of 16-seat passenger buses with a mechanical suspension system. Based on the criteria selected for evaluating smoothness, the research results determined the corresponding limit velocity of smoothness levels for road types B, C, D, and E according to the ISO 8608:2016 standard, which ensures smoothness for passengers and drivers, especially during long trips. The results showed that a smooth feeling is achieved under operating conditions on type B roads with a velocity not exceeding 83.77 km/h, on type C roads with a velocity not exceeding 20.05 km/h, on type D roads with a velocity not exceeding 82.69 km/h, and on type E roads with a velocity not exceeding 19.82 km/h. The working limit is exceeded at a velocity greater than 89.64 km/h on type D roads and a velocity greater than 21.28 km/h on type E roads.