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Note: The following five problems were submitted for a safety workshop given at MnDOT.

Problem # 1: Treatment of a 6-ft deep pond at the edge of the clear zone

It was stated that the clear zone for this obstacle was at or very near to the edge of the 6-ft deep pond. Actually, only the downstream end of the pond was within the clear zone and technically requiring protection based solely on the clear zone concept. However, if one followed that policy and did not protect the upstream end with an appropriate length of need of guardrail protection, would the agency open themselves up to future tort liability? This may be the case since a reasonable engineer and/or designer would likely have protected the entire pond hazard and culvert end with only a small increase in guardrail length.

It was stated that cable barrier was placed down the 10:1 slope in conformance to standards for locating guardrail on slope. Two feet behind the cable barrier posts, the slope changed to a variable slope ranging between 2:1 to 5:1. For the steeper slopes, the three cable barrier may not be capable of safely redirecting the 2000P vehicle at the TL-3 impact condition as it traverses the steeper slopes. Due to this fact, it may have been more appropriate to protect the hazard with strong post W-beam guardrail with an acceptable end terminal. This alternative may have been preferred since the steeper 2:1 slopes on the back side of the posts can be accommodated with this new barrier system.