Why do some of curviest, low dropoff parts of a road have no guardrail? And why are guardrails intermittent on roads?
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I live in AZ. Sometimes there isn’t a good place to mount a guardrail. Let’s say you’re talking about a twisty mountain road that’s been carved into the rock. There may not have been enough space to make the cut wide enough for the minimum lane width plus the extra space for the guardrail. I’ve seen them mounted in the rock on the side but not all rock is created equal. Some of it isn’t suitable for drilling into. You really wouldn’t want to have someone hit the rail and then have the roadway crumble and take more cars with it.
There are federal standards for funded roads. You see lots of guard rails on them. Local roads tend to protect known hazards and area of frequent crashes. Sometimes locals can get federal assistance. You see this when a local road goes under an interstate. The approach for so many feet must be enhanced. They want to be able to park heavy military equipment like tanks on them.
A guardrail is a hazard, since it is a stationary object very near to the highway edge. Engineers try to use other things like shoulders on the edge of highways, striping, delineators, and rumble strips. Some roads are just too narrow to have any of these. Traffic safety isn’t about how you “feel” (eg ‘this is scary’), it’s about fact (‘have cars actually left the road in this area, and will a piece of metal stop them? Yes? Let’s put one here.’).
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