Design, Analysis and Testing of Inflatable Restraint System for Transit Bus Operators

Public transportation system and specifically transit bus systems are key element of the national transportation network in United States. Buses are one of the safest forms of transportation. Nonetheless, bus crashes resulting in operator injuries and fatalities do occur. According to National Transportation Statistics from 1990-2002, the number of transit motor buses in the U.S. has increased by 30% [1]. The majority of fatal crashes involving transit buses result from frontal crashes which could be fatal for bus operators. Therefore, crashworthiness research is a continuing effort. Research has been performed to analyze and improve the safety of transit bus operators.

This paper describes the design, analysis and testing of an inflatable restraint system for a bus operator. At present a three point restraint is the only safety feature implemented on transit buses. The primary objective was to study the level of safety provided by the present safety system. To do this a physical environment of a bus operator compartment was manufactured and this was tested using a 50^th percentile and a 95^th percentile ATD for 18mph frontal impact condition. Acceleration pulse for the sled testing was obtained from a validated finite element model of a typical transit bus [2]. A finite element model of the operator compartment was generated and validated against the test results. This model was used as base line to design the inflatable restraint. A multibody model was created for the same using multibody code MADYMO to run design of experiment to optimize the inflatable restraint system. After achieving a satisfactory design, prototypes were manufactured for further validation of the design. Sled tests were conducted as per the test plan generated based on the simulation results. Results for present design and new design were compared to find the improvement on the level of safety.