For transportation noise applications, the description of the environment, as well as the description of acoustic sources, is complex; and finite-difference time-domain methods have proved their capability to take into account both atmospheric effects and topography. Recently, a time-domain boundary condition has been proposed [Cotté et al., AIAA J. 47, 23912403 (2009)] and implemented in a solver using methods developed in the computational aeroacoustics community [Bogey and Bailly, J. Comput. Phys. 194, 194214 (2004)]. First, propagation of an initial pulse over a distance of 500 m in a two-dimensional geometry is considered in a frequency band up to 1200 Hz. Ground effects are discussed depending on the impedance of the ground, and results are compared with available analytical data. Surface waves, which propagate close to the ground, are exhibited. Then, acoustic scattering by an impedance cylinder in a two-dimensional geometry is considered as a test case to validate the boundary conditions in the presence of an acoustic shadow zone. Comparisons are realized with conformal mapping numerical predictions. At last, a three-dimensional geometry of a railway track is considered to highlight the effects of topography on measurements of railway noise. [This work was performed using HPC resources from GENCI-IDRIS Grant No. 2010-022203.]