  We examine the behavior of $n$ Brownian particles diffusing on the real line
with bounded, measurable drift and bounded, piecewise continuous diffusion
coefficients that depend on the current configuration of particles. Sufficient
conditions are established for the absence and for the presence of triple
collisions among the particles. As an application to the Atlas model for equity
markets, we study a special construction of such systems of diffusing particles
using Brownian motions with reflection on polyhedral domains.
