We investigated the impact of velocity overshoot effect on collector signal delay of bipolar devices by using Monte Carlo simulation method. We found that insertion of an i-layer (lightly doped, intrinsic layer) between base and collector can increase the delay, but the strength of this effect is a function of the i-layer thickness. When the i-layer becomes thinner, the problem of increasing delay seems to disappear. This recovery of delay is realised with a mechanism which is completely different from that in drift-diffusion model.