Physics-Informed Deep Learning for Traffic State Estimation on Freeways: A Comprehensive Comparative Study - Yu, H.; Wang, Y.; Jin, F.; Roncoli, C.; Zhao, M.; Zheng, P.; Guo, J.; Zhang, L. (IEEE Transactions on Intelligent Transportation Systems, Intelligent Transportation Systems, IEEE Transactions on, IEEE Trans. Intell. Transport. Syst., 2026)