The compliance of a Connecticut-designed and -developed impact-attenuation system, the Narrow Connecticut Impact-Attenuation System (NCIAS), with NCHRP Report 350 guidelines is documented. Background information about the system is given, including information on the performance of field installation locations and the availability and cost of installation. NCHRP Report 350 specifies eight full-scale crash tests for redirective/nongating devices. Three of the eight tests were not conducted on the NCIAS because they are similar to three tests conducted under the NCHRP Report 230 requirements, which the NCIAS passed. The five remaining tests were performed. One test was repeated after one of the cylinders was strengthened. All tests were conducted in accordance with the guidelines of NCHRP Report 350 for Test Level 3 devices. The NCIAS passed all requirements for four of the five test designations. It did not pass the requirements for the reverse hit test; therefore, the NCIAS must not be installed at locations where it may be struck from the reverse direction. FHWA has approved the use of the NCIAS on the National Highway System at locations where reverse-direction impacts are unlikely.