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y y y <br />2. Maximum and Minimum Grades <br />a. The maximum grades in percent <br />Design Speed Level Rolling <br />60 3 4 <br />50 4 5 <br />40 5 6 <br />30 9 <br />20 <br />shall be: <br />Mountainous <br />6 <br />7 <br />8 <br />10 <br />12 <br />b. A minimum grade for curbed streets normally <br />should not be less than 0.5 %, a grade of 0.35% <br />may be allowed where there is a high type <br />pavement accurately crowned and in areas where• <br />special drainage conditions may control. <br />c. Grades for 100 feet each way from intersections <br />should not exceed 5 %. <br />d. For streets and roads with projected annual <br />average daily traffic less than 250, short <br />grades less than 500 feet long may be 150% <br />greater. <br />3. Minimum Sight Distances <br />In the interest of public safety, no less than the <br />minimum sight distance applicable shall be provided in <br />every instance. Vertical curves that connect each <br />change in grade shall be provided and calculated using <br />the following parameters. (General practice call for <br />vertical curves to be multiples of 50 feet. Calculated <br />lengths shall be rounded up in each case): <br />Design Speed, MPH 20 30 40 50 60 <br />Stopping Sight Distance - 150 200 275 350 475 <br />Min. Distance, Ft. <br />Desirable Distance Ft. 150 200 300 450 650 <br />Min. K* Value For: <br />Minimum Crest CurvL24 <br />28 <br />55 <br />65 <br />85 <br />145 <br />160 <br />300 <br />Des. Crest Curve <br />28 <br />35 <br />105 <br />Minimum Sag Curve <br />35 <br />6C <br />60 <br />10 <br />100 <br />155 <br />Des. Sag Curve <br />77 <br />- - * K -is a coefficient -by which the algebraic difference in <br />grade may be multiplied to determine the length in feet of the <br />vertical curve which will provide.minimum sight distance. <br />