Rule of thumb?
Rule of thumb?
(OP)
I'm looking for documentation for a "rule of thumb" about sight distance obstructions that goes something like this:
From the travel lane of the approach, hold your hand out at arms length, thumb pointed upwards. If the apparent width of the object is more than twice the width of your thumb, it is a visibility obstruction.
Of course, it depends somewhat on the width of your thumb and the length of your arm.
Is there an accepted width of an object for it to be considered a sight distance obstruction? If so, it is probably an angular measurement rather than an abolute width, since a nearby narrow object can be as obstructive as a wider one farther away.
From the travel lane of the approach, hold your hand out at arms length, thumb pointed upwards. If the apparent width of the object is more than twice the width of your thumb, it is a visibility obstruction.
Of course, it depends somewhat on the width of your thumb and the length of your arm.
Is there an accepted width of an object for it to be considered a sight distance obstruction? If so, it is probably an angular measurement rather than an abolute width, since a nearby narrow object can be as obstructive as a wider one farther away.





RE: Rule of thumb?
KRS Services
www.krs-services.com
RE: Rule of thumb?
RE: Rule of thumb?
Then do as KRS suggests and squat and check. No rule of thumb exists because most people cannot judge distances vs speed vs stopping, etc effectively. In my role as a road safety auditor, I quite often pace out distances, squat on the road, think about what problems may occur etc,and then make a subjective assessment.
Remember at speed, many drivers have very different reaction times, hence the difficulty in assessing what will or will not be an obstruction.
regards
sc