Longitudinal jerk and celeration as measures of safety in bus rapid transit drivers in Tehran

A biomechanical model of a vehicle passenger in the sagittal plane

Musculoskeletal biomechanical models have wide applications in ergonomics, rehabilitation, and injury estimation. Their use can be extended to enable quantitatively explaining and estimating ride comfort for a vehicle's passenger. A biomechanical model of the upper body in the sagittal plane is constructed, which allows for curved motion to simulate the propagation of disturbance energy within a seated passenger aboard a moving vehicle. The dynamic predictions of the model are validated against experimental results within the literature. Frequency responses show that within the vehicular frequency range, the L4L5 and the L5S1 discs in the lower lumbar region are susceptible to the highest vibration transmission. It was also found that vibration transmission is maximized at around 4.5 Hz. The model provides analytical and geometric intuition into the motion of the various segments of the upper body using a few simple geometric assumptions and can be employed to develop a quantitative ride-comfort metric, such that the most comfortable ride would be that which would induce the least internal motion within the passenger model.

Examining the associations between urban bus drivers' rule violations and crash frequency using observational data

Urban bus crashes have been an increasing concern in China thanks to the expansion of urban bus systems. Bus drivers' rule violation behavior appears to be an important factor of bus crashes. However, existing studies rely heavily on questionnaire survey of rule violation behaviors, which may suffer from self-reporting bias. Using observational data of 1,356 bus drivers from onboard video recordings, this paper develops a random parameter zero-inflated Poisson model (with heterogeneity in means and variances) to uncover the relationship between drivers' rule violation behaviors and bus crashes. Model results show that rule violation behaviors such as using a cell phone, driving outside the bus lane, and touching solid line with wheel while driving significantly correlate with crash frequencies with large marginal effects, whereas some other violation behaviors (e.g., running red lights, changing lanes suddenly) show a minor role. This finding highlights the importance of differentiating various rule violations when examining bus crashes instead of aggregating them altogether. Furthermore, the effects of rule violation behavior show substantial heterogeneity. For example, the association between not yielding to pedestrians and bus crashes is enhanced when drivers also show records of touching solid line with wheel while driving, driving outside the bus lane, or are internally trained. Findings of this study provide insights for countermeasures to improve bus safety by targeting critical bus driver groups with specific rule violations, and inform future research to collect observational data on drivers' rule violation behaviors.

Jerk within the Context of Science and Engineering—A Systematic Review

Rapid changes in forces and the resulting changes in acceleration, jerk and higher order derivatives can have undesired consequences beyond the effect of the forces themselves. Jerk can cause injuries in humans and racing animals and induce fatigue cracks in metals and other materials, which may ultimately lead to structure failures. This is a reason that it is used within standards for limits states. Examples of standards which use jerk include amusement rides and lifts. Despite its use in standards and many science and engineering applications, jerk is rarely discussed in university science and engineering textbooks and it remains a relatively unfamiliar concept even in engineering. This paper presents a literature review of the jerk and higher derivatives of displacement, from terminology and historical background to standards, measurements and current applications.