Nebraska LTAP


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Federal requirements have made it mandatory that safe mailbox support systems be designed to yield or breakaway whenimpacted by a vehicle. The Nebraska Department of Transportation (NDOT) has previously used a non-proprietary, U-channel post mailbox support that was evaluated at the Midwest Roadside Safety Facility (MwRSF) in the 1980's. NDOT desires that the mailbox support be updated to meet MASH 2016 TL-3 safety performance criteria and be redesigned to use perforated square steel tubing (PSST) for the mailbox support post.

The objective of this research project is to develop a non-proprietary mailbox support using PSST support posts that is MASH TL-3 compliant. Following a literature review, single and double PSST mailbox support prototypes were developed. The performance of these prototypes was investigated through dynamic component testing under impact conditions similar to MASH test no. 3-61 with a non-compliant, surrogate 1100C vehicle. Test no. NMB-1 impacted both the single and dual PSST mailbox supports in a single vehicle pass at angles of 0- and 10 degrees, respectively. Both PSST mailbox support options performed adequately in the dynamic testing with no issues observed with respect to occupant risk values or occupant compartment deformation or penetration. Recommendations were made following the testing regarding further research and testing of different mailbox configurations and critical impact angles.