ConnDOT: Connecticut Impact Attenuation System - A Crash Cushion

Connecticut Impact Attenuation System - A Crash Cushion


FHWA approves CIAS

as NCHRP Report 350

TL-3 Crash Cushion

April 9, 2002

{CIAS new installation at Exit 32A on I-91}     

  • The Federal Highway Administration (FHWA) has approved the Connecticut Impact Attenuation System (CIAS) for use on the National Highway System at gore areas and other locations where traffic can pass on either side of the array and opposite-direction impacts are not a concern. 

{Connecticut Imact Attenuation System or CIAS as seen from above}

  • The ConnDOT crash test program report on the CIAS is linked to this Web page for viewing, and details the system's compliance with NCHRP 350 requirements.

    The CIAS is a unique "redirective-gating" attenuator that "redirects" vehicles impacting near the back of the unit, or "captures" vehicles when impacted at or near the nose and along its sides .  Below are free downloadable plans.
  • The CIAS consists of 12 steel cylinders, 1.22 m in diameter and 2 cylinders 0.91 m in diameter.  Each cylinder is 1.22 m high,  Wall thickness varies from 6.35 mm for the three cylinders attached to the concrete backup structure to 7.94 mm for the next two cylinders to 4.76 mm for the remaining large diameter cylinders.  The two 0.91 mm diameter cylinders are made from 8-gauge plate steel.
  • The CIAS array is set on two steel skid rails bolted to a concrete pad and connected to a 1980-mm wide concrete backup wall with L-brackets on each side of the wall.  These L-brackets are the only significant modification from the original 1980's design.  The brackets serve to offset the rear most cylinders 610 mm from the edge of the wall to minimize vehicular snagging at this point.
  • This crash cushion was originally  developed in the 1980's and was approved at that time by FHWA under NCHRP 230 criteria.  A change from the original design to meet NCHRP 350 criteria was to reduce the width of the concrete back wall from 2.7 to 2.0 meters. 

{Backwall was narrowed from 2.7 m to 2.0 m.}

NCHRP 350 Crash Tests of CIAS

{CIAS Crash Test, NCHRP 350 test designation 3-33}
CIAS Accident Photographs

Downloadable Plan Sheets for CIAS

Adobe Portable Document Format (PDF) Microstation Design File Format (DGN)
{Adobe PDF of CIAS shop fabrication details}
shop fabrication details PDF shop fabrication details DGN
{Adobe PDF of CIAS pad and backup wall details}
pad & backup wall details PDF pad & backup wall details DGN
{Adobe PDF of CIAS backup wall and assembly details}

backup wall and assembly details PDF

backup wall and assembly details DGN

{Adobe PDF of CIAS fabric cover fabrication and attachment details}

fabric cover fabrication and attachment details PDF

fabric cover fabrication and attachment details DGN

{Adobe PDF of CIAS rear transition details}

rear transition details PDF

rear transition details DGN


Content Last Modified on 9/20/2011 3:11:33 PM