How they work

The barriers are made of three or four steel cables strung on posts. When a car hits the barrier, the posts break and the cables flex, absorbing much of a crash’s kinetic energy. This redirects the vehicle along the median, preventing a cross-median crash.

When a vehicle hits a section of cable barrier, maintenance crews can repair the damaged section quickly. The barriers are carried on steel posts that slide into concrete sleeves. If the barrier is damaged, the posts slide out easily to allow a new cable section to be installed.

In addition to the ability to lessen crash severity, the cable barriers cost less than permanent concrete barriers. The barriers are usually installed in highway sections that include entrance and exit ramps that lead to traffic weaving or a change in the number of lanes that can result in crashes or near-crashes.

As traffic volumes have grown, Minnesota has experienced an increase in cross-median crashes. Installing cable median barriers in strategic locations is an effective method to prevent these often tragic crashes.

Research

MnDOT is conducting a study on the effectiveness of cable median barriers. Preliminary data indicate that no fatal cross-median crashes have occurred at these locations since their installation. Before installation in 2004, the section of I-94 between Maple Grove and Rogers had five fatal cross-median crashes. There are restrictions to where cable median barrier can be installed.

Cost

Material and installation:

• Concrete median barrier: $400,000 to $500,000 per mile
• Cable median barrier: $140,000 to $150,000 per mile

Maintenance (annual cost):

• $7,000 per mile in the Twin Cities metro area
• $6,000 per mile in Greater Minnesota

As traffic volumes grow and the cable median barrier system expands, there will be a significant increase in the cost to maintain the barrier system statewide.