CASS is a Cable Barrier System that consists of C-shaped posts of mild steel that can be either driven, or installed in concrete post foundations with a steel sleeve. Three 19-mm pre-stretched cables are placed in a slot at the top of the post and kept apart by recycled plastic spacers. The cables are tensioned according to the ambient temperature. The tension will vary from 3,150 to 8,100 lb of force. At impact, the posts bend and the cables retain and redirect an impacting vehicle in a smooth and human-friendly way.
CASS was installed along I-5 at Boone Bridge in Oregon. The prime contractor for the installation was Kerr Contracting. The I-5 safety project was prompted by a couple of crossover accidents that resulted in fatalities.
The project was originally programmed for 2006, and it did not specify the type of system to prevent the crossovers. That would be determined by the project team. The local maintenance forces were not at all in favor of continuing the cable system that had been installed on I-5 between Wilsonville and Salem in the late 1990s. They wanted a rigid barrier system.
A crossover that resulted in three fatalities occurred in November 2003. This brought forth an effort to produce a project as soon as possible to close up the median.
"We had been leaning towards a high-tension cable system for this median since learning about the success Oklahoma had with it on one of their freeways," said Allan McDonald, an engineer with the Oregon DOT. "And with the sudden push to get a project out, it left cable as the only practical and affordable alternative to close up six miles of interstate in a short time."
The project was constructed in the summer of 2004.
ODOT maintenance have made eight repairs to the barrier since Nov. 25, 2004, and all of them have been minor (four or five posts) with the exception of one that involved 10 posts and one sleeve.
"I have been very surprised at the amount of hits in this time frame but very pleased with the effectiveness at stopping vehicles, which to this point have been all automobiles from compacts to full size," said William Miller, ODOT transportation maintenance manager, Baldock Section. "I think the biggest surprise is the ease of repairs. We can send out two to three people to do all repairs and be done in a matter of a few hours, where in the past with metal rail repair we would look at four to five people and an all-day event."