This research assesses the design and track operation of a track crawler robot (TCR) for practical and easy inspection of stationary railcars' undercarriages in an effort to detect any pending failures or assess any security risk of out-of-sight objects. The research leverages against a robot available at the Railway Technologies Laboratory (RTL) of Virginia Tech and offers improvements to the structure, drive system, imaging devices, and operator remote control to improve the speed, track maneuverability, and duty cycle of the robot. The TCR includes a drive system consisting of two AC motors that operate a track (like tank tracks). It further includes two GoPro® cameras, light system, and onboard power for approximately one hour of maximum power operation. The details of the TCR design are introduced through its operational requirements, which guided its initial design. The specific design configurations are used to derive the applicable parameters essential for track operation of the robot. The TCR's subsystems are evaluated individually to assess their strengths and weaknesses, which are then used to guide the specific tasks in improving the overall system's performance. The details of the required modifications are included for the imaging, lighting, control, frame structure, and mobility subsystems. For each subsystem, test results are used to engineer workable solutions for overcoming the shortcomings or implementing additional functionality. The redesigned system is further evaluated through testing to assess the improvements due to modifications. Beyond laboratory tests, a final assessment of the system was done on a branch line and mainline track, both with great success. The recorded images and operational evaluation of the TCR prove it to be a valuable inspection tool for the railroads to inspect out-of-sight undercarriage components of stationary trains in a railyard or siding, to identify any failed or nearly-failed equipment before they develop into a major or out-of-compliance issue. The TCR also promises to be useful for security agencies to easily and efficiently inspect trains entering secured areas to uncover any suspicious devices. / Master of Science / This study aims to develop a Track Crawler Robot (TCR) that can assist train operators and security agencies to inspect the undercarriage of trains efficiently and effectively, to detect any pending failure, or to uncover suspicious devices that are not visible train-side. Every day in railyards across the U.S., trains are assembled out of railcars loaded with cargo. The Federal Railroad Administration (FRA) stipulates that each train must be visually inspected before they are allowed to depart to their destination. The undercarriage is difficult, time-consuming, and hazardous to inspect, requiring the inspector to stoop down and partially climb beneath the train. Additionally, the extended length of the trains—some, as long as two miles—and the many components that are part of each railcar makes the inspection an arduous task, and at times leads to missed failures particularly for out-of-site components underneath the carriage. Highly advanced track-mounted vision systems are offered as the means for inspecting trains while in revenue-service operation. Although effective, such systems are expensive and can only inspect the trains passing by their location. Not all trains would pass by the inspection site, and it is possible for a train to pass the site and develop a failure afterward that goes undetected until the next inspection. This research develops a cost-effective, mobile platform, called TCR, that can aid in the undercarriage inspection of stationary railcars. The TCR includes a drive system consisting of two AC motors that operate a track (like tank tracks). It further includes two GoPro® cameras, light system, and onboard power for approximately one hour of maximum power operation. The system gives the inspector a bird's eye view of the undercarriage without the need for a person to crawl in between the tracks. Many tests are conducted to assess the operation of the TCR and make improvements to it to make its captured images clearer and increase its agility and maneuverability. The tests prove to be remarkably successfully, and they confirm TCR's utility for the FRA-mandated train inspections required from the railroads and security inspections desired by the law enforcement and military.