A pedestrian and vehicle barrier system is provided for attaching handrails onto vehicle guardrail barriers. The system comprises an elongate support post member with a slot at a bottom end, to be slid telescopically over a guardrail support post, and sleeved such that it is substantially restricted from moving laterally and/or rotating relative to the guardrail support post. Movement may be further restricted by fasteners. Handrails or other auxiliary barriers may be attached to a top end of the support post member.