The objective of this project was to investigate the feasibility of Raman and fluorescence piezo-spectroscopy as a mobile method to measure the absolute stress in rail. This study identified Raman and fluorescence-sensitive oxides on the rail surface that can be used as an in-situ passive sensor for absolute stress measurement. From a series of material characterization tests, we observed that different iron oxide and hydroxide layers near the rail surface are Raman-sensitive materials, including Hematite  (α-Fe2O3), Goethite (α-FeOOH), Lepidocrocite (ɣ-FeOOH) and Magnetite (Fe3O4). In our Raman piezo-spectroscopy test we found that the Hematite can be used to measure thermal residual stress that is induced when the Hematite layer is formed on rail surface during air quenching after milling at a high temperature. However, the Hematite layer is gradually scaled off over time, and the measurement precision needed to determine a change in stress state exceed the capabilities of the equipment. Much higher resolution equipment is needed to measure small changes in rail stress. Additional experiments were conducted using Aluminum oxide (α-Al2O3), commonly found in thermite weld area. Our test results show that the aluminum oxide has an excellent signal-to-noise ratio to measure rail stress without additional surface treatment. Since it is well established that high contents of aluminum oxides in steel makes the thermite weld brittle, Raman and fluorescence spectrometry could be used as a non-contact quality assurance method to inspect chemical (Al2O3 and iron oxides) and mechanical (residual stress) conditions of exothermic welds in field.