What is the classification of the track allowed for freight speed with a rail joint having both tread and gage mismatch issues?

The classification of the track that allows for freight speed with a rail joint experiencing both tread and gauge mismatch issues is indeed Class 3. In railroading, various track classes are defined based on the speed of trains that can safely operate on them. Each class corresponds to specific track conditions and requirements.

For Class 3 track, the maximum allowable speed for freight trains is up to 40 mph. However, the presence of mismatched tread and gauge at a rail joint indicates that there are significant irregularities which can affect train stability and safety. This type of track may still be classified as Class 3 if it meets other criteria for structural integrity and if the extent of the mismatch does not exceed defined limits.

In contrast, lower classes such as Class 1 and Class 2 would typically not support higher speeds even with minor defects, and Class 4 allows for faster speeds but requires stricter maintenance and quality standards that would likely not accommodate the issues stated in the question. Thus, Class 3 reflects a balance where some impairment exists but the infrastructure remains fundamentally functional for freight operations at specified speeds.