Fig. 1. Diagram of beam propagation

Fig. 2. Framework of road meteorology sensor system

Fig. 3. Experimental system diagram

Fig. 4. Picture of sensor

Fig. 5. Experimental road

Fig. 6. Meteorological state measurement data of asphalt road under different angles

Fig. 7. Meteorological state measurement data of stone road under different angles

Fig. 8. Experimental data set of the variation of $R^{\mathrm{1310}}$ with the seeper thickness

Fig. 9. Experimental data set of the variation of $R^{\mathrm{1}\mathrm{430}}$ with the seeper thickness

Fig. 10. Error analysis of thickness measurement of seeper

Fig. 11. Experimental data set of the variation of $R^{\mathrm{1}\mathrm{310}}$ with the ice thickness

Fig. 12. Error analysis of thickness measurement of ice