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How do sight triangles work?  



Pictured below is a sight triangle shown as right of way, I am interested if anyone knows why sight triangles seem to vary.  The one I have attached is shown as right of way, which means the minimum set back line is effected by site triangle since it is shown as right of way.   This site triangle below is 150'x150'. I have recently seen one that was 125'x125' and the minimum building line was not effected and  it appeared to be shown as an easement on the other plat.  Does someone perhaps know if there are more than one type of site triangle or if one can be taken as right of way versus an easement?  Should this effect the minimum building line as shown?

Thanks and any insight is welcomed.



Site Triangle
This topic was modified 12 months ago 3 times by jebryant


The map is correct. The sight triangle is typically called out as "additional r/w" within the deed.
The building setback would be as drawn unless there is local ordinance language that states otherwise.

11 Answers

Keeping obstructions out of that triangle is the goal.  The building set back shown is entirely outside of the triangle.  Thus, no problem.

If the sight triangle were to cross the standard building set back, that would be wrong.  The set back would then need to be overruled by the necessity of the triangle.  But, there would be no need for an additional building set back distance from the triangle..


I agree with most of the comments above regarding local rules and regulations.

I also have another possibility in mind.

Depending on what type of map/plan was shown in the original post, the "MBL" may have been established as part of a plat or development plan approved by the local jurisdiction.  Perhaps it has been set back from the sight triangle, as opposed to the apparent ROW line, due to concessions that the developer made to the jurisdiction or perhaps even because the developer was intending a certain look and feel within the subdivision.

Or there could be road widening plans in the future and the extra setback will be needed to clear the anticipated future improvements.

I have worked in 3 states and several dozen local jurisdictions over my career and can think of other alternatives.

So, short answer - it depends.

What type of map is shown in the OP?


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Pitt County; NCDOT Division 2, District 1. (based on info shown in uploads of OP)

I'd start with the surveyor of record on each of the two maps. Give them a call and see what the platting requirements/ governing jurisdictions were (expected to be DOT and Pitt County with the little information shown). That conversation should reveal why the triangles are there and what jurisdiction required them (County's don't own roads in NC so, I put my money on DOT).

If that doesn't get you on target, go to the source of the requirement and ask. Guessing district engineer or county planners.

You've already got a good description of 'sight triangles', easements and rights-of-way from previous posts.

IMO: you are over-thinking the purpose (well described above) of a sight triangle. They are required, and enforced, to improve safety along travel ways. Don't put any obstructions within them, unless they conform with the guidelines of the governing jurisdiction.


I'm not a surveyor, but I may be able to answer your question. The proper term is "sight triangle" and it has to do with the proximity of obstructions such as signs or plants near intersections. Placement of such obstructions is regulated so that they do not block the line of sight of drivers entering intersections.  A tall sign placed near the curb of an intersection would invite accidents.

There are local laws as well as state laws. This piece from Huntersville, NC gives a very good explanation.



This is the one that made me scratch my head.  It doesn't effect the line here.

The part that has me confused is it effecting the minimum building line.




that can't be drawn to scale


It's 125' measured along each centerline


That I don't know, but local building codes probably address it. It seems reasonable that a building within the sight triangle would be a hazard, though.


Zoning ordinance requires a 40' set back from the right of way. That's where the confusion begins. I see sight triangles listed as right of ways and easements. So i have researched quite a bit without finding out what makes one an easement or a right of way. The pic above conflicts with the other as a best I can tell.  The thing is, if it is truly a right of way it basically doubles the set back line.

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Zoning codes are unlikely to include "intersection sight distance triangles" these are based on engineering design of the road and speed limits.  The Ohio Department of Transportation standards include this chart

addressing both horizontal and vertical sight distance requirements in relation to design speed (usually higher than the planned speed limit) of the through street.


Would that mean that the first picture posted is incorrect? The minimum building line would not be measured from the site triangle?

I am having trouble determining where the minimum set back line should be measured from.

If the sight triangle is right of way, and the zoning ordinance says measure from the right of way, would you measure from the site triangle line or of the highway right of way line?

That would depend on how the right of way was taken/established. In Ohio the sight distance triangle may be a visual obstruction easement (as Dave Lindell mentioned) and not part of the actual right of way. In some areas the law and engineering design standards may require permanent easement or fee take of the triangle.


Sight triangles in the city where I used to work were for keeping fences and hedges and other obstructions below a certain height, say 36 inches, within the triangle.


I find it interesting that local agencies limited the property owners right of use of their property within some theoretical triangle and then the same local agencies load the area between r/w and curb face with bus stops, street trees, transformers, road signs, traffic control boxes.......with no consideration for line of sight safety that is needed for safe vehicle movements. One of my pet peeves when driving. Jp


BTW, it would be good to learn more about the terms right-of-way and easement and when, and if, they are different.  Too many times the intent is one thing and the interpretation is another.  Typically a building set back is from the edge of the property, which in the general case is also the edge of a road (whether in fee or easement/ROW).  Additional easements, such as utility or drainage easements may parallel that property line/ROW.  That does not impact the building set back, unless some male donkey has screwed up.

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generally and depending on your locale, site triangles or sight distance has to do with a vehicle at an intersection (15' back from edge travelway) with a persons 'head' at 3.5' above ground and looking at incoming vehicles from both directions.  The angle is relative to the speed limit and location of the vehicle in the travel lane.  For more information, look at AASHTO standards - 'Geometric Design of Highways and Streets'.  This is important as wrongly computing same and allowing an obstruction within that area can contribute to the cause of an accident.



Easements and setbacks can be tricky legal terms that need to be defined and quantified according to law. I would expect language to be associated with any setback to list exceptions and conditions of it. 

In an urban area where there may not be any building setback lines, sight triangles can be ground based and thus a building can be over the easement area if it allows for clear line of sight. Canopies, and floors and above could be exempt from the triangle restriction unless grade deems otherwise.  Other than that, all of the above. 


PDF page 7 clears up the easement/right of way question for Charlotte, NC.

This one from Monmouth NJ indicates that the easement can't be subject to a mortgage which would seem to exclude it from any foreclosure.

It does seem more complicated than just street geometry.

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