A Manual for Assessing Safety Hardware (MASH) Test Level 3 (TL-3) approach guardrail transition (AGT) was designed to connect the Midwest Guardrail System to a MASH TL-4 steel tube bridge rail, designated Steel Railing, Type IL-OH. The AGT connection consisted of a 34 in. tall thrie-beam AGT, HSS83631=4 transition tube rails that aligned with the lower and middle bridge rail tubes, and new connection hardware designed to prevent vehicle snag during impacts. The new AGT connection was evaluated using a combination of LS-DYNA finite element analysis software and full-scale crash testing in accordance with MASH TL-3 impact criteria. The critical impact points were selected using LS-DYNA for MASH test nos. 3-20 and 3-21. In test SBRTR-1, a 2,404 lb small car struck the AGT at a speed of 64.6 mph, an angle of 25.2°, and at a location 21.3 in. upstream from the last transition post. In test SBRTR-2, a 5,007 lb quad cab pickup truck struck the AGT at a speed of 62.7 mph, an angle of 24.9°, and at a location 15.9 in. upstream from the last transition post. The small car and pickup truck were both contained and redirected and the tests resulted in a successful evaluation according to MASH TL-3 safety performance criteria. Implementation guidance for the new AGT in various configurations is provided.