Severe railcar responses can result from crosslevel and vertical rail inputs. At low speeds rail joint excitation can coincide with the roll natural frequency of a vehicle. At high speeds, dynamic effects can cause high wheel loads and harsh ride for sensitive cargos. Computer simulation of these and other vertical dynamic effects cans assist in design selections of vehicle components and diagnosis of troublesome vehicle responses. Many dynamic models available today lack the complexity to analyze accurately some of the important dynamic effects. In this report a 28-degree-of-freedom railcar model has been developed to analyze the vertical dynamic responses of railcars subjected to random and deterministic track inputs. This model features carbody vertical bending and torsional modes, multiple component trucks and suspensions, and rail irregularity inputs at each of the eight wheels. Simulation results for a 100-ton vehicle operating on harmonic track inputs compare favorably with the AAR Flexible Carbody Model. Other simulations on random track evaluate the influence of auxiliary viscous stabilizers and increased payloads on railcar responses. These simulations demonstrate the effectiveness of the computer simulation as a design and analysis tool. / M.S.