breakaway support post 130 is preferably installed with webs 134 and pivot pin 154 extending generally normal from the associated guardrail 22 as a result of this orientation webs 134 and rotatable coupling assembly 140 including pivot pin 154 allow breakaway support post 130 to sufficiently support guardrail 22 during a rail face impact to redirect an impacting vehicle back onto the associated roadway in fig4 and 6 respective webs 134 of upper portion 142 and lower portion 144 are shown generally aligned parallel with each other for some applications the orientation of lower portion 144 may be varied with respect to upper portion 142 such that web 134 of lower portion 144 extends approximately parallel with guardrail 22 the attachment of brackets 150 and 152 with their respective upper portion 142 and lower portion 144 may be modified to accommodate various orientations of lower portion 144 relative to upper portion 142 depending upon the length of lower portion 144 and the type of soil conditions soil plates 162 and 164 may be attached to lower portion 144 extending from respective flanges 136 and 138 for some applications lower portion 144 may be substantially longer than upper portion 142 as a result of increasing the length of lower portion 144 the use of soil plates 162 and 164 may not be required shear pin 156 is laterally inserted through adjacent portions of brackets 150 and 152 offset from pivot pin 154 shear pin 156 preferably has a relatively small cross section as.