Method for measurements of speed limiting obstacles and ride comfort in vehicles

Abstract: In this thesis a method is developed for measuring accelerations generated by speed limiting measure. The purpose is, besides developing the method, also to generate threshold values between experienced discomfort and measured accelerations. The accelerations, which the vehicles passengers is exposed to when passing a speed limiting measure, is measured to generate this relation. The vibration measurements have been performed beneath the vehicle seat with equipment that measure accelerations in three directions during the passage of the speed bumps The total acceleration over a speed limiting obstacle was calculated and to be able to connect the total force with the experienced discomfort trials have been performed using volunteers. The volunteers answered a questionnaire while travelling over the speed limiting obstacles. The questionnaire consisted of questions concerning what discomfort the passengers experienced. The discomfort was described on a scale of six degrees from comfortable to extreme uncomfortable. There were 47 persons included in the main study, of which 23 was women and 24 men. They each travelled over all speed reducing measurements and answered the questionnaire at the same time. Men had worse attitude to speed humps and drove three times as much than women. A scale that contains the threshold values for the different levels of discomfort has been developed for speed bumps and roundabouts. For roundabouts there weren’t enough observations to create a reliable scale. The analyses showed that no differences exist between how men and women experienced the discomfort. There also was no difference how drivers and passengers in the front seat experienced the discomfort. Despite the facts that speed bumps are of the same kind there are great differences between how the speed bumps are designed. There was no distinction that a certain kind of speed bump was better or worse than the others. The differences depended on the design of each speed bump The method developed can be used as a tool to investigate the function of already existing speed bumps. It can also be used when developing new speed bumps to achieve right speed reduction.