LARIMER COUNTY RURAL AREA ROAD STANDARDS

Chapter 4 – Road Design and Technical CriteriaSection 4.3 Road DesignTable 4-1Road Standards – Technical Design CriteriaCollectorDesign Element Arterial Major Minor Local RoadsDesign SpeedPosted Speed50 - 6045 - 5545 - 6040 - 5535 - 5035 - 452525Minimum centerline radius NA 1039’-NA 510’-NA 165’(with no super-elevation)Maximum super-elevation 0.08 ft/ft 0.08 ft/ft 0.08 ft/ft NAMinimum tangent between 400’ 400’ 200’ 100’curves or at intersectionsMinimum Centerline arc 400’ 300’ 300’ 100’lengthsMax Centerline Gradeflat/rolling8%8% 8% 8%Mountains10%10% 10% 10%Minimum Centerline 0.5% 0.5% 0.5% 0.5%GradeMinimum Crest 84-151* 61-151 29-84 12K-values for Sag 96-136 79-136 49-96 26Vertical Curves*Right of Way (ROW) Width 120’ 100’ 80’ 70’* Range varies based on design speed.e. Off-Site Design Centerline, Flowlines and Cross Sections. To assure thatfuture road improvements will meet these Standards the design of thecenterline, flowline, and cross sections of all roads, except cul-de-sacs, shallbe continued for 500 feet beyond the proposed construction. The grade andground lines of all Arterials shall be continued for a total of 1000 feet beyondthe end of the proposed construction.f. Overlay Areas. At a minimum, areas that will be overlayed must be designedto show at least a typical cross section for the area to be overlayed; a planview with notes depicting areas that need: a leveling course, taper milling,patching, fabric, etc.; and notes about accesses and shouldering. Additionalinformation may be required by the Engineer depending on the situation.4.3.2.2 Vertical Alignmenta. Maximum and Minimum Grades for Roads. The maximum and minimumgrades for specific road classifications are shown in to Table 4-1.b. Grade Breaks. No single point grade break shall exceed 0.50 percent.c. Requirements for Using Vertical Curves. Vertical curves are required forgrade changes that exceed 0.50 percent. A series of grade breaks may beused in lieu of a specified vertical curve as long as the series of breaks meetthe vertical curve criteria in these Standards for the design speed. K-valuesfor design shall conform to Table 4-1.Larimer County Rural Area Road Standards Page 4-3October 22, 2007