Iroad Appendix B Contents: Notes on Slopes and Grades

Vulcan supports specification of grades, slopes and crossfalls in three ways - as decimal angular units, as a ratio grade specification or as a percentage grade. For example, the grades 4.573921, 1:12.5, and 8% all represent the same physical gradient.

To represent a gradient we can use:

• Angle notation (decimal degrees or gradians depending upon your preferences), i.e. angle = A.
• Ratio notation where the grade is specified as the ratio of the sides a and b, i.e. a:b where a/b=tan(A).
• Percentage rise/fall notation where the grade = D%, i.e. a/b* 100%.

The following strings are all valid specifications of grade:

4.56446
0.03
-34.7
1:10
10:1
1:123.4
1:-10
5%
6.9%
-4.0%