When is cable median barrier preferable?August 11th, 2006 by sitedude
The in basket: We’ve been exploring the workings and
practicality of cable median barrier in Road Warrior this week.
I asked what commends it over other kinds of barrier and why it’s usually installed close to one pair of lanes rather than in the middle of the median. In a few places, it is put on both sides of the median
The in basket: We’ve been exploring the workings and practicality of cable median barrier in Road Warrior this week.
In addition to the areas covered (Wednesday?) I asked what commends it over other kinds of barrier and why it’s usually installed close to one pair of lanes rather than in the middle of the median. In a few places, it is put on both sides of the median
The out basket: Lisa Murdock of the Olympic Region of state highways said cable median barrier flexes up to 12 feet, allows drivers to safely stop the vehicle without re-entering traffic, allows water to pass underneath and is best in conjunction with wide medians
Normal guardrail flexes up to three feet. allows drivers some control after impacts, lets water pass beneath it and is often used above steep slopes.
Concrete barrier has little or no flexibility, often redirects cars back into traffic and is best where traffic moves in opposite directions in close quarters, where there’s no room for a median.
“Occupants of vehicles striking cable barrier are less likely to be injured or killed than those striking concrete barrier or guardrail,” she said. “This is partly because cable barrier is far less likely to redirect an errant vehicle into a second vehicle in the collision.”
“Statewide, cable barrier successfully restrained 95 percent of errant vehicles without involving a second vehicle. In comparison, only 67 to 75 percent of crashes with W-beam guardrail and concrete barrier (did). When one vehicle crashes into another during a collision, the risk of injury and the number of injuries increase.”
The median’s slope and wetlands or dangerous obstacles in the median dictate installation on the shoulders, rather than the middle, she said.
“In locations where there is nothing in the median, but cable barrier is on both sides, it’s because we installed the cable barrier less than 10 feet from the fog line to avoid wetlands. This cable barrier can flex up to 10 feet. We didn’t want cars crossing the median and having the cable barrier flex into the oncoming lanes.” Having it on both sides helps prevent that.