Iroad Appendix B Contents

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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%