LARIMER COUNTY RURAL AREA ROAD STANDARDS

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CHAPTER 4 – ROAD DESIGN AND TECHNICAL CRITERIA4.1 GENERALThe provisions stipulated in this section are general in nature and shall be considered asapplicable to all parts of these specifications, including any supplements and revisions. Allconstruction within the public right-of-way shall be designed by or under the direct supervision ofa registered professional engineer, licensed to practice in the State of Colorado. All drawingsand support data submitted to the County for approval must bear the engineer’s seal andsignature.A. The design criteria, as presented, are intended to aid in preparation of plans andspecifications, and include minimum standards where applicable.B. These design criteria are considered minimum and a complete design willusually require more than is presented in this document.C. As with any design criteria, occasions may arise where the minimum standards areeither inappropriate or cannot be justified economically. In these cases a variance tothese criteria shall be considered. Written request for each variance shall bedirected to the Engineer and shall conform to criteria in "Variance Requests" found inChapter 1. Design of all roads shall conform to this document, the County’sTransportation Plan (TP), any and all applicable County planning documents, CDOTRoadway Design Manual (latest edition), Standard Plans M & S Standards (latestedition), the Manual on Uniform Traffic Control Devices (MUTCD), and AASHTO APolicy on Geometric Design of Highways and Streets (latest edition).D. This chapter defines layout criteria and other design criteria that shall be followed forlocating and designing all roads located in unincorporated Larimer County identifiedin the Larimer County Land Use Code except those areas located within a Town orCity’s Growth Management Area where the County, through an IGA, has agreed toapply different standards.E. The standards and requirements contained in this manual and chapter only apply torural, unincorporated areas, and areas outside of County acknowledged GrowthManagement Areas. Proposed “urban” level developments and improvements inthese areas are not covered by this manual and are not allowed unless approved inwriting by the Engineer. If approved by the Engineer, the proposed “urban” levelimprovements must at a minimum conform to the requirements of this manual as wellas the applicable sections of the Larimer County Urban Area Street Standards(LCUASS). In these instances, the Engineer will determine which requirements ofthe LCUASS apply. Examples of “urban” level improvements include, but are notlimited to: curb and gutter, sidewalks, pedestrian ramps, stormdrain inlets, sidewalkchases, crosspans, medians, traffic signals, etc.4.2 NEW ROADSThe TP shall be used for establishing approximate locations of Major roads. The Engineer shallhold approval authority for specific locations, retain the authority to designate collector roads,and retain authority for approval of the overall road layout.All roads shall have a logical relationship to the existing topography and to the location ofexisting or platted roads within adjacent properties.Larimer County Rural Area Road Standards Page 4-1October 22, 2007
Chapter 4 – Road Design and Technical CriteriaSection 4.3 Road Design4.3 ROAD DESIGN4.3.1 ClassificationsAll roads are classified as Arterial, Collector or Local roads. These classifications relateto the function of the roads. Lower order roads function primarily as access to individuallots, and higher order roads function primarily for the purpose of mobility (expeditiousmovement of people and goods). Larimer County has adopted an expandedclassifications system that is to be used within the County except for areas withinrecognized GMA’s in which case the County may, at its discretion apply the City orTown’s functional classification of roadways.4.3.2 AlignmentHorizontal and vertical road alignments should conform to existing land layout plus thefollowing criteria:4.3.2.1 Horizontal AlignmentOn Arterial and Major Collector roadways, curve radii and tangents shall be as largeas possible using the minimums only where necessary. Angle point directionchanges are not allowed. All changes in direction shall be made using standardcurves.a. Horizontal Curve Radii. The minimum allowable centerline radii forhorizontal curves shall be as designated in Table 4-1. Reverse andcompound curves should be used only when a single radius curve will notwork. For driver safety, compound curves shall have a ratio no greater than1.5 where the value of the larger radius is divided by the smaller radius.b. Minimum Tangent Length. Requirements are as follows:1) Intersection. Whenever a minor road intersects a road of higherclassification, a tangent length (measured from the nearest edge ofpavement of the intersected road to the point of curvature in theintersecting road) shall be provided for a safe sight distance and safetraffic operation. The minimum required tangent lengths indicated in Table4-1 apply to the minor leg(s) only. The angle of departure shall notexceed 10 degrees for the length of tangent.2) Reverse Curves. The tangent between reverse curves shall be no lessthan the length shown in Table 4-1.3) Broken Back Curves. Two curves in the same direction (broken backcurves) shall be separated by a tangent with a length of at least 2 timesthe minimum length shown in Table 4-1.c. Curves with Small Deflection Angles (10° or less). To reduce theappearance of kinks in the road, minimum lengths of curve shall be designedwith minimum centerline arc lengths as shown in Table 4-1.d. Horizontal Curves on Vertical Curves. For driver safety, horizontal curvesshall not begin near the top of a crest vertical curve nor near the bottom of asag vertical curve.Larimer County Rural Area Road Standards Page 4-2October 22, 2007
Page 1 and 2: LARIMER COUNTYRURAL AREA ROAD STAND
Page 3 and 4: Table of Contents3.3.11 Typical Str
Page 5 and 6: Table of ContentsCHAPTER 8 - ENVIRO
Page 7 and 8: Table of Contents12.3.7.2 Conventio
Page 9 and 10: Table of ContentsG.7.12 Other Permi
Page 11 and 12: Chapter 1 - General InformationSect
Page 17 and 18: Chapter 2 - Submittal ProceduresSec
Page 19 and 20: Chapter 2 - Submittal ProceduresSec
Page 21 and 22: Chapter 3 - Submittal Requirements
Page 23 and 24: Chapter 3 - Submittal Requirements
Page 25: Chapter 3 - Submittal Requirements
Page 29 and 30: Chapter 4 - Road Design and Technic
Page 35 and 36: 4.9.1.7 Design VehiclesChapter 4 -
Page 39 and 40: CHAPTER 5 - GEOTECHNICAL STANDARDS
Page 41 and 42: Chapter 5 - Geotechnical Standards
Page 49 and 50: Chapter 6 - STORMWATER MANAGEMENTSe
Page 51 and 52: Chapter 7 - Bridges and Major Drain
Page 53 and 54: Chapter 8 - Environmental and Agric
Page 55 and 56: Chapter 8 - Environmental and Agric
Page 57 and 58: 9.1.3 DefinitionsChapter 9 - Roadwa
Page 59 and 60: CHAPTER 10 - ACCESS REQUIREMENTS AN
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Chapter 12 - Right of Way Permittin
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Appendix A - Definitions and Abbrev
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Appendix A - Definitions and Abbrev
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APPENDIX B - REFERENCES AND RESOURC
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APPENDIX D - CONSTRUCTION STANDARDS
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Appendix D - Construction Standards
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APPENDIX E - CONSTRUCTION TESTING F
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Appendix F - Guidelines for Traffic
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APPENDIX G - DESIGN AND CONSTRUCTIO
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Appendix G - Design and Constructio
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Appendix H - General NotesSection H
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APPENDIX I - VARIANCE REQUEST SUBMI
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LARIMER COUNTY RURAL AREA ROAD STANDARDS

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