I see this happens in Power Civil South Africa SS4 as well as the latest version of Open Roads Designer EAP

When you draw a curve return for an intersection with an ahead taper on a straight line the taper criteria is honored as per the image below

No the same taper but from the curve return

The intersection is shifted to the inside of a horizontal curve and you can see that the taper with its rules

Now below you can see the ahead tapers rule is not honored:

Although it states the rule it does not match the stand alone offset taper.

The same was replicated in OR-EAP

Your thoughts?

  • This is logged as a defect 673585 and is on the list to be addressed. The reason is the 'Curve with taper' assumes the tangent at end of the taper to define the offset / ratio from and this results in this shift.

    The correct construction can be achieved by running the fillet without the taper and include an offset, then run the ratio offset taper command to achieve the desired results.