At what point would the vegetation behind the guardrail be too thick that it may change the way the guardrail works?
Varying degrees of …
Trees: 4”+ as in the roadside design guide.
Evergreen bushes: Does size of the braches or height have guidance?
Shrubs: ?
Grasses: ?
Here is my first impression:
I would expect small annual and perennial flowers to be acceptable and not drastically change vehicle-barrier performance.
I would expect small to medium, largely-spaced bushes (shrubs) or medium to tall, moderately-spaced natural grasses to be acceptable and not drastically change vehicle-barrier performance.
I may expect large, largely-spaced bushes or tall, closely-spaced, clumped, natural grasses to be acceptable and minorly change vehicle-barrier performance.
I may expect large, closely-spaced bushes to be marginally acceptable and cause concern for vehicle-barrier performance.
I may expect small, largely-spaced trees to create marginal safety performance and moderately change vehicle-barrier performance.
I would expect presence of 2 to 4” diameter trees near barriers to cause concerns: ramping, excessive OIV, etc.
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