How do I know if there is enough sight distance at an intersection?
There are several answers to this questions, but a good minimum is that all types of vehicles should be able to safely turn from all legs of the intersection. In order to do this, they need to be able to see approaching vehicles with enough time to make any maneuvers safely. Table 5 (page 34) of the Traffic Sign Handbook shows the critical distances for stopping and turning at an intersection. If you cannot see the distances as given in the chart, you may need signage and may want to restrict access.
Also, you can use a simple rule of thumb to know if there may be a safety issue due to approaching vehicles. Set yourself at the location where a vehicle’s driver would be when turning and count the time from when you can see an approaching vehicle until it gets to the intersection. (You may be able to just do this in a car or pick-up, but you may need to stand off to one side of the road to be safe) If there is not at least 7 seconds between when you see the vehicle and it gets to the intersection, the sight distance may be limited. Obviously there are many other factors, but this rule can at least let you know if you may have issues to deal with. Be sure to check for vehicles in all directions.
More details on sight distance and other intersection safety questions can be found in the Cornell Local Roads Program workbook Road Safety Fundamentals.
Road Safety Fundamentals (pdf)