Researchers developed a second-generation RAdar Ballast Inspection Tool (RABIT) based on ground-penetrating radar (GPR) for use by track inspectors. This system is much lighter (26 lbs/11.8 kg) than its predecessor and is portable. It has a single bi-static antenna pair that straddles the tie, enabling the ballast properties under the tie to be measured. During a measurement, the RABIT rolls down the track and obtains average ballast properties over a span of 10 cribs, thereby reducing problems associated with local variability in ballast properties and tie geometry. Researchers collected measurements and ground truth data at 12 test track locations and 84 in-service track locations. The research team trained a neural network to map GPR waveforms to ballast fouling and moisture estimates. The correlation factor between the RABIT estimates and measured values determined from physical ballast samples was greater than 0.9.