We study the well-posedness and the deterministic many particle limits for second order Follow-the-Leader type models involving challenging nonlinearities which naturally appear in the modelling of crowd dynamics. We aim to validate the second-order particle approach for a class of traffic models characterised by the intrinsic mechanism that the reaction-time of the drivers depends on both inertial and congestion terms. We also consider the many particle limit in the vanishing inertia regime to recover the expected transport equation with nonlinear mobility. This is a joint work with D. Mazzoleni and F. Riva.