3-bounded property in a triangle-free distance-regular graph

AbstractLet Γ denote a distance-regular graph with classical parameters (D,b,α,β) and D≥3. Assume the intersection numbers a1=0 and a2≠0. We show that Γ is 3-bounded in the sense of the article [C. Weng, D-bounded distance-regular graphs, European Journal of Combinatorics 18 (1997) 211–229]