Vibration tests on transit buses

This report describes a vibration measurement program which was performed on two transit buses to quantify the vibration environment for Automatic Vehicle Monitoring (AVM) equipment. Test routes included road conditions ranging from smooth city streets, of the types encountered during the greatest majority of normal usage, to random bumpy streets. However, to extend the higher end of the vibration data, parts of the runs were made at speeds which were considered abnormally fast for the road condition being traversed. Vibration was measured by recording the calibrated output signal from accelerometers on oscillograph rolls during significant combinations of road and bus operating conditions. Accelerometers were located in the three areas on the buses corresponding to the location at which AVM equipment will be positioned. Normal operating conditions produced maximum peak-to-peak vibration levels of 2g or less. Higher vibration levels were recorded during the program, but these were associated with unusually severe bus operating conditions or with special tests. Both buses exhibited approximately the same vibration levels for comparable conditions. On both buses, vibration on the dashboard exhibited the highest amplitude. Within the limitations of the recording method used and the control over test conditions, this program has supplied a definition of the vibration environment typical of transit buses used in city route service.