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HomeMy WebLinkAboutSUB201800145 Review Comments Final Plat 2019-02-15County of Albemarle Department of Community Development Memorandum To: Troy Wade From: Paty Saternye- Senior Planner Division: Planning Services Date: October 24, 2018 Rev. 1: January 25, 2019 Rev. 1: UPDATE: January 28, 2019 Rev. 2: February 5, 2019 Rev. 2 UPDATE: February 15, 2019 Subject: SUB-2018-145 Barracks Farm — Subdivision Plat The County of Albemarle Planning Division will grant or recommend approval of the Final Plat referenced above once the following comments have been addressed: [Each comment is preceded by the applicable reference, which is to the Subdivision/Zoning Ordinances unless otherwise specified.] [14-302 (A)(3), (4), (6) & 14-303 (E)] Private Easements; Alleys and shared driveways; Dimension standards and information on all lots, streets, alleys, easements, and shared driveways; Existing or platted streets. The existing "40' Right of Way Easement has been accepted as a private street in previous subdivision plats. However, the following must be addressed: b) & g) Rev. 2 UPDATE: This is a combined comment from Rev. 2: 215119. See the 215119 comments for more detail. Provide 1 or 2 maintenance agreement(s) that specifies that the streets from the VDOT right of way to 150' beyond the start of the proposed parcel meet the standards specified. Please refer to the template maintenance agreement and checklist for review of private improvements maintenance instruments provided with previous comments. Please also note that for the first portion of the private street, (in TM44-27D) prior to the fork, it must meet the 6-lot VDOT (county private) road standard but beyond the fork it must only meet the 3-5 lot road standard. See an attached engineering comments as well as an email and the "Guidelines for Geometric Design..." supplied by engineering. The additional items are to provide information on what is required for the 6-Lot VDOT (County Private) requirements. The proposed maintenance agreement(s) must specify the appropriate standards for the specific portion of the private street. c), d) & f) Rev. 2 UPDATE: This is a combined comment from Rev. 2: 215119. See the 215119 comments for more detail. Revise the plat so that the proposed roadway widths are provided in the portion of the private street from the VDOT right of way to 150' beyond the start of the proposed parcel. These dimensions must meet the standards specified by engineering and mentioned above. 13. [14-302 (B)(1)] General Information. When revising the plat include a date of last revision on the plat. This date should be updated prior to each resubmission. Rev. 1: Comment still valid. Address this comment after making the two other specified change below. Rev. 2: Comment not fully addressed. Address this comment after making the two other specified change below. Rev. 2 UPDATE: Comment not fully addressed. Address this comment after addressing the other plat specific comments. 15. [Comment] See the attached comments from the other reviewers. Rev. 1: See the attached comments from the other reviewers. Rev. 2: Comment not fully addressed. See the attached comments from the other reviewers. Rev. 2 UPDATE: Comment not fully addressed. See the attached comments from the other reviewers. 16. Rev. 2 UPDATE: As previously specified by enpineerinp, the private street must be built or bonded prior to approval of this subdivision plat. Please contact Paty Saternye at the Department of Community Development 296-5832 ext. 3250 for further information. COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902-4596 Phone (434) 296-5832 Fax (434) 972-4126 Subdivision Plat review Project: Barracks Farm Road Final (2-Lot) Subdivision Plat (SUB2018-00145) Plat preparer: John Carroll, Lake Anna Land Surveyors, 362 Overton Dr., Mineral, VA 23117 Owner or rep.: Barracks Farm LLC, 518 Barracks Farm Rd, Charlottesville, VA 22901 Applicant: Troy and Marianna Wade, 107 Fairway Dr, Louisa, VA 23093 [troy(i�i amisondaviscompany. com] Plan received date: 31 Aug 2018 (Rev. 1) 2 Jan 2019 Date of comments: 14 Sep 2018 (Rev. 1) 22 Jan 2019; comments revised: 5 Feb 2019 Reviewer: John Anderson /Engineering Planning Reviewer: Paty Satemye We have completed Engineering review of plat dated 12-7-18. After further discussion with Planning Division, Engineering review comments are revised. SUB2018-00145 _deleted i 0/24 ii 8 2. Show and label critical slopes on plat. Ref. Exhibit. (Rev. 1) Addressed. 3. Show and label stream buffers not shown. Ref. Exhibit. (Rev. 1) Addressed. 4. Note 2: Provide date of (current) field survey. (Rev. 1) Addressed. 5. Provide tie for farm road centerline at 800.39' residue boundary line. (Rev. 1) Addressed. 6. For L3 + 442.59 segment, provide total length in parenthesis (514.59'). (Rev. 1) Comment withdrawn. Review error: total distance—442.59'. 7. For 3.0 Ac. parcel boundary north of proposed drain field, show 354.56 as total length, if such is the case. (Rev. 1) Comment withdrawn. 8. For 362.00' boundary of 3 Ac. parcel, list bearing with /at distance label (N35°07'05"E). (Rev. 1) Addressed. 9. For L10 tie (which is L5), provide (TIE) label with L5. (Rev. 1) Addressed. 10. Recommend stream buffers be shown as dot -dash line type, not solid line. (Rev. 1) Addressed. i i. deleted l 0/24 it 8 (review o or) n a/b. deleted 10/24/18 12. Shift L7 label so it is not obscured by residue boundary line. (Rev. 1) Addressed. 13. Provide bearing/distance or curve data for farm road centerline between C5 and C6. (Rev. 1) Addressed. 14. New: Code 14-412.A.2 applies. With subdivision, Barracks Farm Road, a private road, will serve 5 parcels/lots: TMPs: 44-22 (residue); 44-22B; 44-22C; 44-22C1; 44-22D (ref. image, below), and three lots over ^ distance of 2,714'{4E).—Provide a PE scale drawing to confirm a private street constructed to standards listed at 14-412.A.2. exists oveF this distan^R. between end state maintenance and a point 150' beyond entrance to parcel 44-22D, prior to subdivision plat approval. Standards include: 1. A turnaround meeting AASHTO guideline, required at a point just beyond 518 / 516 Barracks Farm Road driveway (a shared driveway ap - �ars to serve 518 and 516). (5 Feb, REVISED) Comment withdrawn. Existing intersections internal to TMP #44-22 (Residue) provide adequate turnaround. Current roadway Engineering Review Comments Page 2 of 5 evaluated adequate to ACF&R needs, ref. review comment (1/22/19; CV): "The driving surface up to the development site is wider than shown on the plans and sufficient for emergency vehicle access. Fire Rescue has no objection to this lot being developed but any further development on this road will require upgrades in width and surface." 2. Vertical centerline curvature meets a minimum design K value of five (5) for crest curves and fifteen (15) for sag curves (provide street profile /K-values). (5 Feb, rev.) Comment withdrawn. GIS terrain contours indicate road meets vertical centerline curvature minimum design K values for crest /sag curves. 3. Street easement is thirty (30) feet, minimum. (5 Feb, rev.) As follow-up: Please dimension access easement width on TMP #44-27D. 4. Radius of horizontal curvature is forty (40) feet or greater. (5 Feb, rev.) Comment withdrawn. GIS terrain contours indicate road meets horizontal curvature, forty (40) feet or greater. GIS image (vertical /horizontal geometry) 5. Travelway width is fourteen (14) feet, minimum. (5 Feb, rev.) Asefollow-up: Requirement applies at property entrance, at pillars. Ref. 14-412(A)2(a). Where additional width is required, compacted VDOT 2 1 A stone, 6"-8" depth may be placed, and compacted with sheepsfoot roller or similar equipment to match existing asphalt grade and cross slope, including at pillars, between end state maintenance exterior to TMP 44-22 (Residue) and a short distance interior to the parcel. Applicant -furnished field measurements on 31- Jan 2019 indicate roadway width is at least 14' near end state maintenance but is 12'-8" at pillars and is again >14' wide at a point 45' interior to the parcel. Once required minimum 14' width is constructed at points currently less than 14' wide, and shoulders are established (next item, item #6), submit written notification to Albemarle County /Engineering Division that roadway improvements are complete. Engineering Review Comments Page 3 of 5 Engineering will inspect to confirm. Roadway improvements must be built or bonded prior to subdivision plat approval. 6. Three (3) foot minimum shoulder width. (5 Feb, rev.) As follow-up: Requirement applies at property entrance, even at pillars. Establish 3' shoulder width, minimum. Minimum travelway plus minimum shoulder width requires a minimum twenty (20) foot opening between pillars. A pillar must be relocated. Also, ensure shoulder cross slope adequate to avoid stormwater detention at the pavement edge, for entire length of roadway, from end state maintenance to 150' past proposed entrance to parcel 44-22D. Image, below, pg. 4-12, AASHTO Green book. Also, VDOT Road Design Manual, Appendix B1, pg. B(1)-8, Tah1P 2 4-12 I A Policy on Geometric Design of Highways and Streets It should be noted that rigid adherence to the shoulder crj4 slope criteria presented in this chapter may reduce traffic operational efficiency if the shoulder cross slope criteria are applied without regard to the cross section of the paved surface. On tangent or long -radius curved alignment with normal crown and turf shoulders, the maximum algebraic difference in the traveled way and shoulder grades should be from 6 to 7 percent. Although this maximum algebraic difference in slopes is not desirable, it is tolerable due to the benefits gained in pavement stability by avoiding stormwater detention at the pavement edge. 7. Minimum of four (4) feet from edge of shoulder to ditch centerline. (5 Feb, rev.) Comment withdrawn. A ditch is not required given relatively flat terrain and absence of existing ditch features. If ditch requirement imposed, there is no existing network with which to connect at either end of roadway section under consideration. Runoff is from paved surface to shoulder, and from shoulder to undeveloped fields. 8. Grade < 16% calculated over a distance fifty (50) feet. (5 Feb, rev.) Comment withdrawn. GIS terrain contours indicate grade <16% calculated over a distance of fifty (50) feet, from end state maintenance to 150' beyond entrance to parcel 44-22D. 9. Rectangular zone super -adjacent to the street clear of all obstruction, including any structures and vegetation, that is at least fourteen (14) feet in width and fourteen (14) feet in height. (5 Feb, rev.) As follow-up: Requirement also applies at pillars. A pillar must be relocated. 10. If the grade of any portion of the street exceeds seven (7) percent, the entire street shall be surfaced as required by VDOT standards. Streets having a grade of seven (7) percent or less may have a gravel surface. (1.-10., unless otherwise authorized by Chapter 14, Albemarle County Code) (5 Feb, rev.) Comment withdrawn. GIS terrain contours indicate no portion of the street exceeds seven (7) percent. In any event, existing surface is asphalt pavement. Road. Fr-em this point on, 2 lat standard listed a4 14 4 12.A. 1. applies, and He PE sealed ep-As� street t ..oin4s 1.0...,n 519 i 516 R.,,-.,acks IF Road.) (5 Feb, rev.) Comment withdrawn. Existing intersections internal to 44-22 (Residue) provide adequate turnaround. Also, item # 14.(1.), above. 15. New: Revise plat to show street easement is thirty (30) feet, minimum. (5 Feb, rev.) Withdrawn; redundant, listed at 14.3., above. 16. New: Recommend revise residue label to read `150.162 Acres.' (5 Feb, rev.) Addressed via email (.PDF revision) to Planning Div. 17. Note: Albemarle has option to request a separate road plan application, but will accept a PE sealed s drawing of constructed improvements. in either- ease (Read Plan' As built), o ,...to . plie .t;,... w th appropriate FeVieWfee is FeEtdifed. 1H ei.1er 6aSe, appr-aval of As bttilt drawing ei- Read Plan design is re"ir-ed194ei- to final subdivision plat appFo ^'. If Applicant elects to submits a Road Plan that proposes improvements, aswould appear to be the case (Ex width -- ' ^'' then Road Plan improvements would need to be built, or improvements bonded, prior to final plat approval. Engineering Review Comments Page 4of5 County GIS: TMPs 44-22 (residue), 44-22C, 44-22C1 (44-22D not shown; created with subdivision) After discussion with Planning, 10/24, original comments 1., 11. deleted (review error). Engineering meets with Applicants to discuss project review comments on a weekly basis, Thursday, 2-4 pm. Please let us know if you would like to schedule a meeting with Engineering. Please feel free to call if any questions: 434.296-5832 —0069. Thank you Albemarle County Code, 14-412, partial Engineering Review Comments Page 5 of 5 2. Streets serving three to five lots. Each private street serving three (3) to five (5) lots shall satisfy the following: (i) vertical centerline curvature shall meet a minimum design K value of five (5) for crest curves and fifteen (15) for sag curves; (ii) sight distances shall not be less than one hundred (100) feet; (iii) turnarounds shall be provided at the end of each street per American Association of State Highway and Transportation Officials guidelines; (iv) street easements or right-of-way widths shall be thirty (30) feet minimum; and (v) the radius for horizontal curvature shall be forty (40) feet or greater, unless otherwise authorized by this chapter. Any standard in this paragraph (2) may be reduced to the standard for streets serving two (2) lots where a driveway departs from the street and two lots remain to be served, and a turnaround is provided. In addition, the following shall also apply: (a) Private streets in the rural areas. For such private streets in the rural areas: (i) travelway widths shall be fourteen (14) feet minimum, with three (3) feet minimum shoulder widths, and a minimum of four (4) feet from the edge of the shoulder to the ditch centerline; (ii) the grade shall not exceed sixteen (16) percent calculated over a distance fifty (50) feet; (iii) if the grade of any 14-60 Supp. 431, 7-14 ALBEMARLE COUNTY CODE portion of the street exceeds seven (7) percent, the entire street shall be surfaced as required by Virginia Department of Transportation standards; streets having a grade of seven (7) percent or less may have a gravel surface; and (iv) the street shall have a rectangular zone superjacent to the street that is clear of all obstructions, including any structures and vegetation, that is at least fourteen (14) feet in width and fourteen (14) feet in height. SUB201800145 Barracks Farm 2-lot FPT 012219-rev 020519 Patricia Saternye Subject: FW: RE: Barracks Farm --- SUB201800145 Attachments: AASHTO Guidelines for Geometric Design of Very Low -Volume 2001 Exhibits 1 and 12.pdf From: John Anderson Sent: Thursday, February 14, 2019 2:36 PM To: Patricia Saternye <psaternye@albemarle.org> Cc: Bill Fritz <BFRITZ@albemarle.org> Subject: RE: Barracks Farm --- SUB201800145 Paty, Thanks for speaking with me. I understand the section of road you have in mind. For portion of road beyond VDOT right-of-way that is private yet subject to the 6-lot VDOT (county private) road standard prior to the fork (with portion of road continuing onto Applicant's parcel, where 3-5 lot standard applies), photos indicate the existing total roadway width is at least 20'. Total roadway width includes shoulders. Engineering relies on AASHTO Guidelines for Geometric Design of Very Low -Volume Local Roads (ADT<400), in this instance; specifically, Exhibit 1. Functional classification Minor Access minimum total roadway design width is 18-ft., at design speeds up to 40mph. AASHTO forms basis of VDOT standards. Existing conditon of portion of Barracks Farm Road beyond state ROW subject to the 6-lot standard is acceptable. Please ref. Attached. Thanks again —please let me know if you have any questions. -best, JA -x3069 John Anderson, PE, Civil Engineer II • (434) 296-5832 -x3069 Community Development Dept. I Engineering Division County of Albemarle 1 401 McIntire Road Charlottesville, Virginia 22902-4596 Guidelines for Geometric Design of Very Low -Volume Local Roads (ADT:5 400) American Association of State Highway and Transportation Officials 444 !forth Capitol St., N.V , Suite 240 Washington, DC 20001 (202) 624-5800 www.transportation.org M Copyright 2001, by the American Association of State Highway and Transportation Officials. All Rights Reserved. This book, or parts thereof, may not be reproduced in any form without written permission of the publisher. Printed in the United States of America. ISBN:1-56051-166-4 © 2001 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. CHAPTER 4 DESIGN GUIDELINES This chapter presents design guidelines for specific aspects of the design of very low -volume local roads including cross section (traveled way and shoulder widths), horizontal alignment, stopping sight distance, intersection sight distance, roadside design, unpaved roads, and two-way single -lane roads. CROSS SECTION The key elements of cross section design for a roadway are traveled way width and shoulder width. Cross section design criteria for lower volume roads generally address total roadway width (traveled way plus shoulders) rather than having separate criteria for lane and shoulder width. Many lower volume roadways have no painted edgelines and do not have paved shoulders of a material that contrasts with the traveled -way pavement, so there may be no clear demarcation between the traveled way and shoulders. Design guidelines for cross section in new construction projects and on existing very low -volume local roads are presented below. New Construction The design guidelines for cross section in new construction projects on very low -volume local roads differ between rural and urban areas. Each set of design guidelines is presented below. While the quantitative design guidelines for new construction address only total roadway widths, designers should also give consideration to the appropriate right-of-way width. In new construction projects, ample right-of-way should be obtained, whenever practical, to accommodate possible future widening of the roadway. Very Low -Volume Local Roads in Rural Areas Exhibit 1 presents the guidelines for total roadway widths for newly constructed roads in rural areas. The total roadway width criteria vary from 5.4 to 8.0 m [18 to 26 ft] with the functional subclass and the design speed of the road. These values were developed in research by Neuman (3) from several sources. The primary source for cross section widths was NCHRP Report 362 (5); other sources included TRB Special Report 214 (4), the United States Forest Service (USFS) (11), and the Transportation Association of Canada (12). 17 © 2001 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. AASHTO-Guidelines for Geometric Design of Very Low -Volume Local Roads (ADT __<400) Metric Total roadway width (m) by functional subclass Design Industrial/ speed Major Minor Recreational commercial Resource Agricultural (km/h) access access and scenic access recovery access 20 - 5.4 5.4 6.0 6.0 6.6 30 - 5.4 5.4 6.0 6.0 7.2 40 5.4 5.4 5.4 6.4 6.4 7.2 50 5.4 5.4 5.4 6.8 6.8 7.2 60 5.4 5.4 5.4 6.8 6.8 7.2 70 6.0 6.0 6.0 7.0 - 8.0 80 6.0 6.0 6.0 7.4 - - 90 6.6 - 6.6 - - - 100 6.6 - - - - - US Customary Total roadway width (ft) by functional subclass Design Industrial/ speed Major Recreational commercial Resource Agricultural (mph) access Minor access and scenic access recovery access 15 - 18.0 18.0 20.0 20.0 22.0 20 - 18.0 18.0 20.0 20.0 24.0 25 18.0 18.0 18.0 21.0 21.0 24.0 30 18.0 18.0 18.0 22.5 22.5 24.0 35 18.0 18.0 18.0 22.5 22.5 24.0 40 18.0 18.0 20.0 22.5 - 24.0 45 20.0 20.0 20.0 23.0 - 26.0 50 20.0 20.0 20.0 24.5 - - 55 22.0 - 22.0 - - - 60 22.0 - - Note: Total roadway width includes the width of both traveled way and shoulders. Exhibit 1. Guidelines for Total Roadway Width for New Construction of Very Low -Volume Local Roads in Rural Areas The cross section width guidelines for major access roads, minor access roads, and recreation and scenic roads are based primarily on travel by passenger cars and recreational vehicles. Widths for industrial/commercial access roads, resource recovery roads, and agricultural roads consider more frequent use by larger trucks and, in the case of agricultural access roads, use by wide agricultural equipment. These greater widths for industrial/commercial access roads, resource recovery roads, and agricultural access roads reflect the otitracking and maneuverability requirements and the greater widths of the larger vehicles using these roads. The ability of vehicles in opposing directions of travel to pass one another is an important design consideration for rural roads. Access past parked vehicles is not a major concern because parking on rural roads 18 © 2001 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. Guidelines is not common. The increased cross section widths for industrial/commercial access roads, resource recovery roads, and agricultural access roads should not be construed as a safety requirement. It should be noted that the roadway widths for agricultural access roads are applicable on roads used by agricultural equipment wider than a typical 2.6-m [8.5-ft] truck. The choice of the appropriate functional subclass is key to determining the appropriate roadway width. Where minimum roadway widths are used for a selected functional subclass, the designer should consider providing a wider roadway at sharp horizontal curves. By contrast, widths less than the minimums shown in Exhibit 1 may be appropriate adjacent to historic structures or in mountainous terrain. In determining appropriate roadway widths, the designer should refer to the discussion of design flexibility in Chapter 3. Designers should be afforded great discretion in the use of Exhibit 1, even for new construction. Small differences in the existing or proposed dimensions from those shown in Exhibit 1 may be completely acceptable. For example, on roads used by trucks or wider agricultural equipment, designers should have the discretion to consider the actual widths of vehicles expected to use a particular road and modify the width guidelines in Exhibit 1 accordingly. Very Low -Volume Local Roads in Urban Areas As in rural areas, the cross section width guidelines for very low -volume local roads in urban areas are related to basic operational requirements. Speeds are lower, trip lengths and lengths of local roads are generally much shorter, and available right-of-way width is much less than in rural areas. The major functional requirements for very low -volume local roads in urban areas include the ability for vehicles in opposite directions to pass one another, the need for vehicles to pass parked or stopped vehicles, the need to provide access for fire trucks and other emergency vehicles, and the need to accommodate occasional larger delivery vehicles. Cross section widths for urban major access roads and urban industrial/commercial access roads should generally be the same as those shown for comparable rural roads in Exhibit 1. Greater widths are desirable where parking is permitted. Cross section width guidelines for urban residential streets are shown in Exhibit 2. These widths incorporate consideration of access for fire trucks and other emergency vehicles and apply to streets where parking is permitted on both sides of the roadway. Reduced widths may be appropriate where parking is restricted. These guidelines are based on the ITE Recommended Guidelines for Subdivision Streets (13). 19 © 2001 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. When the height of eye (h1) and height of object (h2) are 1,080 mm and 600 mm [3.5 ft and 2.0 ft], respectively, as used for stopping sight distance, Equations (5) and (6) become: Metric US Customary When S is less than L, When S is less than L, AS2 _ AS2 L 658 L 2158 (7 ) When S is greater than L, When S is greater than L, L=2S-658 L=2S-2158 A A (g) Exhibit 12 presents the rate of vertical curvature, K, that will provide stopping sight distance for crest vertical curves on very low -volume local roads. The appropriate length for a vertical curve can generally be determined by multiplying the K-value in Exhibit 12 by the algebraic difference in grade between the adjoining tangents. Sag Vertical Curves There are no special guidelines for design of sag vertical curves on very low -volume local roads. Sag vertical curves should generally be designed in accordance with Chapter 5 of the AASHTO Policy on Geometric Design of Highways and Streets (1). Existing Roads Given the geometry of stopping sight distance on horizontal and crest vertical curves, the costs for even marginal or incremental improvements make reconstruction of very low -volume local roads to increase stopping sight distance not cost-effective except in unusual cases. Research NCHRP Report 400 (7) found that, even on higher volume roadways, accidents associated with limited sight distance are extremely rare events. Furthermore, there was no indication that lengthening of the sight distance of a crest vertical curve has any demonstrable effect on reducing the number of collisions. Collisions related to limited sight distance are even less likely on very low -volume local roads than on the higher volume roads studied in NCHRP Report 400 (7). 38 © 2001 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. Design Guidelines Metric All locations for 0-100 vpd and "lower "Higher risk" locations for 100-250 vpd risk" locations for 100-250 vpd' and all locations for 250-400 vpd 2 Stopping Rate of vertical Stopping Rate of vertical Design sight curvature, K3 sight curvature, K3 speed distance distance (km/h) m Calculated Design m Calculated Design 20 15 0.3 0.5 15 0.3 0.5 30 25 0.9 1 30 1.4 2 40 35 1.9 2 40 2.4 4 50 45 3.1 4 55 4.6 5 60 60 5.5 6 70 7.4 8 70 75 8.5 9 90 12.3 13 80 95 13.7 14 110 18.4 19 90 120 21.9 22 130 25.7 26 100 140 29.8 30 155 36.5 37 US Customary All locations for 0-100 vpd and "lower "Higher risk" locations for 100-250 vpd risk" locations for 100-250 vpd' and all locations for 250-400 vpd 2 Stopping Rate of vertical Stopping Rate of vertical Design sight curvature, K3 sight curvature, K3 speed distance distance (mph) ft Calculated Design ft Calculated Design 15 65 2.0 2 65 2.0 2 20 90 3.8 4 95 4.2 5 25 115 6.1 7 125 7.2 8 30 135 8.4 9 165 12.6 13 35 170 13.4 14 205 19.5 20 40 215 21.4 22 250 29.0 29 45 260 31.3 32 300 41.7 42 50 310 44.5 45 350 56.8 57 55 365 61.7 62 405 76.0 76 60 435 87.7 88 470 102.4 103 ' "lower risk" locations are locations away from intersections, narrow bridges, railroad - highway grade crossings, sharp curves, and steep grades 2 "higher risk" locations are locations near intersections, narrow bridges, or railroad - highway grade crossings, or in advance of sharp curves or steep downgrades 3 the rate of vertical curvature, K, is the length of curve (L) per percent algebraic difference in intersecting grades (A); i.e., K = L/A. Exhibit 12. Guidelines for Minimum Rate of Vertical Curvature to Provide Design Stopping Sight Distance on Crest Vertical Curves for New Construction of Very Low -Volume Local Roads Because sight distance improvements are unlikely to be cost-effective under most circumstances, the existing sight distance on a very low -volume local road may be allowed to remain in place unless there is evidence of a site -specific safety problem attributable to inadequate sight distance. If a site -specific safety problem is identified, and if the designer finds after investigation that the safety problem is attributable to limited sight distance, then the sight 39 © 2001 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. distance of the specific horizontal or vertical curve(s) at which the problem is present should be upgraded to at least the sight distance levels shown in Exhibit 8 as part of any reconstruction project undertaken. Sight distance could be increased to the full criteria presented in the AASHTO Policy on Geometric Design of Highways and Streets (1) where the judgment of the designer indicates that this is appropriate. This approach is intended to provide maximum flexibility to the designer in assessing site -specific conditions and exercising informed judgment to decide whether a correctable problem is present or not. Guidance concerning identification of site -specific safety problems is found in Chapter 3 of these guidelines. INTERSECTION SIGHT DISTANCE General Considerations Each intersection has the potential for several different types of vehicle -vehicle conflicts. The possibility of these conflicts actually occurring can be greatly reduced through the provision of proper sight distances and appropriate traffic controls. The avoidance of crashes and the efficiency of traffic operations still depend on the judgment, capabilities, and response of each individual driver. The driver of a vehicle approaching an at -grade intersection should have an unobstructed view of the entire intersection, including any intersection traffic -control devices, and sufficient lengths of the intersecting road to permit the driver to anticipate and avoid potential collisions. The sight distance that should be used for design under various assumptions of physical conditions and driver behavior is directly related to vehicle speeds and to the resultant distances traversed during perception -reaction time and braking. Guidelines for intersection sight distance at intersections between very low -volume local roads are presented here. However, if one or more of the intersection legs has a design traffic volume that exceeds 400 vehicles per day, intersection sight distance should be designed in accordance with Chapter 9 of the AASHTO Policy on Geometric Design of Highways and Streets (1). Stopping sight distance is provided continuously along each road or street so that drivers have a view of the roadway ahead that is sufficient to allow drivers to stop, if necessary, under prescribed conditions. The provision of stopping sight distance at all locations along each road or street, including intersection approaches, is fundamental to safe intersection operations. Vehicles are assigned the right-of-way at intersections by traffic -control devices or, where no traffic -control devices are present, by the rules of the road. A basic rule of the road is that, at an intersection at which no traffic -control devices are present, the vehicle on the left must yield the right-of-way to the vehicle on the right if they arrive at approximately the same time. Sight distance is provided at intersections to allow the drivers of vehicles without the right-of-way to perceive the presence of potentially conflicting vehicles in sufficient time for the vehicle without the right-of-way to stop, if necessary, before reaching the intersection. The methods for determining the sight distances needed by drivers approaching intersections are based on the 40 © 2001 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.