The primary purposes of this study are to: (1) establish the vibration characteristics of a typical locomotive cab used in freight locomotives in North America; and (2) evaluate the effect of various structural modifications on the cab interior noise and vibrations. To this end, the structural dynamics of a production locomotive cab is studied in a laboratory environment. The cab is excited with a hydraulic actuator in a manner closely resembling the input the cab is subjected to in the field. A series of tests are conducted to establish the vibration baseline of the cab, and to define how various parts of the cab vibrate. Next, a series of modifications are made to the cab floor and roof structures to reduce vibration levels. The test results show that stiffening the cab floor reduces the interior cab noise and vibration at frequencies below 200 Hz. This reduction, however, occurs at the expense of increased vibrations at higher frequencies. A similar compromise is noticed when damping material is added to the roof structure of the cab. The addition of damping materials lowered some of the acceleration peaks, while it increased a peak occurring at 53 Hz. The results of this study indicate that, in practice, different noise and vibration solutions may have to be tried out before a determination can be made on which solution is the most effective for a particular application. Of course, such determination is possible only after the noise and vibration characteristics of the structure and the main causes of the noise have been identified. The laboratory setup that will be described in this study is particularly effective in creating an environment that is conducive to accurate and repeatable measurements of different noise and vibration solutions, while the cab structure is excited in the same manner as it is in the field. Without such a setup the effect of many solutions may not be accurately determined.