Abstract: A breakaway support post (18, 210) is provided for a highway guardrail system (10) to enhance safety of a vehicle impacting with either the rail face of the guardrail (16) or one end of the guardrail facing oncoming traffic. The breakaway support post may have upper and lower portions (26, 28) with releasable coupling assembly (29, 211) disposed therebetween to maintain the upper and lower portions generally aligned prior to impact of a vehicle with one end of the guardrail. The breakaway support post may also have releasable coupling (301) disposed between the upper and lower portions and cable (303). The releasable coupling may allow the upper portion to separate from the lower portion. The cable may be released during separation of the upper and lower portions. The coupling assembly preferably provides sufficient support during a rail face impact to direct an impacting vehicle back onto the roadway.