what is a  delta angle
big highway image by Galyna Andrushko from <a href='http://www.fotolia.com'>Fotolia.com</a>. A delta angle, a term well known to civil engineers, is a measurement used in designing roadways. The delta angle is used to make other relevant calculations, or it can be determined using known measurements. A delta angle is the measurement in degrees where two straight lines, also known as tangents, intersect. A horizontal circular curve is a mathematical calculation determining the optimal arc between two tangents. The measurement of the central curve on the arc is equal to the delta angle.