steep road guardrail or sandtrap design ? 1

[roncity]

On a steep, curvy, residential road, drivers lose control in wet weather and hit guardrails and mailboxes. Somewhere I've seen sand traps or pits placed on the outside of the pavement to stop cars and trucks. What are these things called?
I've goggled all sorts of words and can't find any references...
Any other suggestions to assist drivers? The pavement is asphalt and has been grooved and milled to a very rough texture; and is not a problem in dry weather. But during rain events, drivers lose control and leave the pavement.
Standard "slick when wet" signs are in place with 20 MPH advisory speeds

 

[ACtrafficengr]

You're looking for "truck escape ramps."

Does the road have proper cross slope? If it's too steep, that might contribute to people going off the road. If it's too flat, water may be running down the travel lanes instead of going off the side.

If it's curbed, does it have enough catch basins to get the water off the road?

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[Maury]

Visibility may be a contributing factor. Is the lighting adequate?

 

[cvg]

If cars are leaving the rain during ordinary wet weather, they are traveling much too fast! try speed bumps or other traffic calming/slowing methods.

I don't believe the sand escape ramps will help much. They are really meant for trucks going down long, steep grades, such as in the mountains. The brakes go out due to constant braking and generation of high temperatures and therefore the trucks begin to pick up speed and lose control.