230.1 Horizontal Alignment - Revision history

Legged1: /* 230.1.5 Spiral Transition Curves */ RR#3810

2024-01-18T15:43:50Z

230.1.5 Spiral Transition Curves: RR#3810

← Older revision		Revision as of 10:43, 18 January 2024
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	==230.1.5 Spiral Transition Curves==		==230.1.5 Spiral Transition Curves==

	Spiral curves are used on all roadways that have design traffic greater than 400 vehicles per day and ~~an anticipated posted speed limit greater~~ than ~~50 mph. See~~ [https://www.modot.org/media/16812 Standard Plan 203.20] ~~for the maximum curve radius for use with spiral curve transitions~~. The length of spiral is the same as the length of superelevation and widening transition given in [https://www.modot.org/media/16819 Standard Plan 203.22].		Spiral curves are used on all roadways that have design traffic greater than 400 vehicles per day and have a radius less than the values listed on [https://www.modot.org/media/16812 Standard Plan 203.20]. The length of spiral is the same as the length of superelevation and widening transition given in [https://www.modot.org/media/16819 Standard Plan 203.22].

	==230.1.6 Sight Distance==		==230.1.6 Sight Distance==

Smithk: /* 230.1.4 Superelevation and Widening */

2019-08-08T15:17:16Z

230.1.4 Superelevation and Widening

← Older revision		Revision as of 10:17, 8 August 2019
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	==230.1.4 Superelevation and Widening==		==230.1.4 Superelevation and Widening==

	Superelevation rate and widening for various design categories are given on [https://www.modot.org/media/16812 Standard Plan 203.20] and [https://www.modot.org/media/16818 Standard Plan 203.21] while the length of transitions are provided in [https://www.modot.org/media/16819 Standard Plan 203.22]. For divided pavements with narrow medians of 16 ft. or less in width, the superelevation runoff length for undivided roadways is used. For multiple lane roadways, the superelevation runoff length is multiplied by the appropriate factor based on the number of lanes. In urban areas where roadways with more than four lanes intersect at grade, consideration is given to reducing the pavement cross slope to minimize the difference in elevation between the extreme edges of the travelways. The difference in the rate of cross slopes for adjacent lanes should not exceed 5%, or 0.05 ft./ft. When the plans utilize the data given on the standard plans, only the maximum rate of superelevation and the maximum widening are shown with the horizontal curve data on the plans. Complete details of the superelevation and widening transition must be given on the plans if the standard plans details are not used.		Superelevation rate and widening for various design categories are given on [https://www.modot.org/media/16812 Standard Plan 203.20] and [https://www.modot.org/media/16818 Standard Plan 203.21], while the length of transitions are provided in [https://www.modot.org/media/16819 Standard Plan 203.22]. For divided pavements with narrow medians of 16 ft. or less in width, the superelevation runoff length for undivided roadways is used. For multiple lane roadways, the superelevation runoff length is multiplied by the appropriate factor based on the number of lanes. In urban areas where roadways with more than four lanes intersect at grade, consideration is given to reducing the pavement cross slope to minimize the difference in elevation between the extreme edges of the travelways. The difference in the rate of cross slopes for adjacent lanes should not exceed 5%, or 0.05 ft./ft. When the plans utilize the data given on the standard plans, only the maximum rate of superelevation and the maximum widening are shown with the horizontal curve data on the plans. Complete details of the superelevation and widening transition must be given on the plans if the standard plans details are not used.

	==230.1.5 Spiral Transition Curves==		==230.1.5 Spiral Transition Curves==

Smithk: /* 230.1.4 Superelevation and Widening */The proper usage of Std. Plans was clarified.

2019-08-08T15:16:28Z

230.1.4 Superelevation and Widening: The proper usage of Std. Plans was clarified.

← Older revision		Revision as of 10:16, 8 August 2019
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	==230.1.4 Superelevation and Widening==		==230.1.4 Superelevation and Widening==

	Superelevation rate, widening~~, and length of transition~~ for various design categories are given on [https://www.modot.org/media/16812 Standard Plan 203.20] and [https://www.modot.org/media/16818 Standard Plan 203.21]. For divided pavements with narrow medians of 16 ft. or less in width, the superelevation runoff length for undivided roadways is used. For multiple lane roadways, the superelevation runoff length is multiplied by the appropriate factor based on the number of lanes. In urban areas where roadways with more than four lanes intersect at grade, consideration is given to reducing the pavement cross slope to minimize the difference in elevation between the extreme edges of the travelways. The difference in the rate of cross slopes for adjacent lanes should not exceed 5%, or 0.05 ft./ft. When the plans utilize the data given on the standard plans, only the maximum rate of superelevation and the maximum widening are shown with the horizontal curve data on the plans. Complete details of the superelevation and widening transition must be given on the plans if the standard plans details are not used.		Superelevation rate and widening for various design categories are given on [https://www.modot.org/media/16812 Standard Plan 203.20] and [https://www.modot.org/media/16818 Standard Plan 203.21] while the length of transitions are provided in [https://www.modot.org/media/16819 Standard Plan 203.22]. For divided pavements with narrow medians of 16 ft. or less in width, the superelevation runoff length for undivided roadways is used. For multiple lane roadways, the superelevation runoff length is multiplied by the appropriate factor based on the number of lanes. In urban areas where roadways with more than four lanes intersect at grade, consideration is given to reducing the pavement cross slope to minimize the difference in elevation between the extreme edges of the travelways. The difference in the rate of cross slopes for adjacent lanes should not exceed 5%, or 0.05 ft./ft. When the plans utilize the data given on the standard plans, only the maximum rate of superelevation and the maximum widening are shown with the horizontal curve data on the plans. Complete details of the superelevation and widening transition must be given on the plans if the standard plans details are not used.

	==230.1.5 Spiral Transition Curves==		==230.1.5 Spiral Transition Curves==

Smithk: updated link to std plans

2018-12-07T17:11:20Z

updated link to std plans

← Older revision		Revision as of 12:11, 7 December 2018
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	\|[[media:Green Book Fig 3-23.pdf\|'''Green Book Figure 3-23''' "Diagram Illustrating Components for Horizontal Sight Distance"]]		\|[[media:Green Book Fig 3-23.pdf\|'''Green Book Figure 3-23''' "Diagram Illustrating Components for Horizontal Sight Distance"]]
	\|-		\|-
	\|[~~http~~://www.modot.~~mo.gov/business/standards_and_specs~~/~~documents~~/~~20320.pdf~~ Standard Plan 203.20]		\|[https://www.modot.org/media/16812 Standard Plan 203.20]
	\|-		\|-
	\|[~~http~~://www.modot.~~mo.gov/business/standards_and_specs~~/~~documents~~/~~20321.pdf~~ Standard Plan 203.21]		\|[https://www.modot.org/media/16818 Standard Plan 203.21]
	\|-		\|-
	\|}		\|}
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	==230.1.4 Superelevation and Widening==		==230.1.4 Superelevation and Widening==

	Superelevation rate, widening, and length of transition for various design categories are given on [~~http~~://www.modot.~~mo.gov/business/standards_and_specs~~/~~documents~~/~~20320.pdf~~ Standard Plan 203.20] and [~~http~~://www.modot.~~mo.gov/business/standards_and_specs~~/~~documents~~/~~20321.pdf~~ Standard Plan 203.21]. For divided pavements with narrow medians of 16 ft. or less in width, the superelevation runoff length for undivided roadways is used. For multiple lane roadways, the superelevation runoff length is multiplied by the appropriate factor based on the number of lanes. In urban areas where roadways with more than four lanes intersect at grade, consideration is given to reducing the pavement cross slope to minimize the difference in elevation between the extreme edges of the travelways. The difference in the rate of cross slopes for adjacent lanes should not exceed 5%, or 0.05 ft./ft. When the plans utilize the data given on the standard plans, only the maximum rate of superelevation and the maximum widening are shown with the horizontal curve data on the plans. Complete details of the superelevation and widening transition must be given on the plans if the standard plans details are not used.		Superelevation rate, widening, and length of transition for various design categories are given on [https://www.modot.org/media/16812 Standard Plan 203.20] and [https://www.modot.org/media/16818 Standard Plan 203.21]. For divided pavements with narrow medians of 16 ft. or less in width, the superelevation runoff length for undivided roadways is used. For multiple lane roadways, the superelevation runoff length is multiplied by the appropriate factor based on the number of lanes. In urban areas where roadways with more than four lanes intersect at grade, consideration is given to reducing the pavement cross slope to minimize the difference in elevation between the extreme edges of the travelways. The difference in the rate of cross slopes for adjacent lanes should not exceed 5%, or 0.05 ft./ft. When the plans utilize the data given on the standard plans, only the maximum rate of superelevation and the maximum widening are shown with the horizontal curve data on the plans. Complete details of the superelevation and widening transition must be given on the plans if the standard plans details are not used.

	==230.1.5 Spiral Transition Curves==		==230.1.5 Spiral Transition Curves==

	Spiral curves are used on all roadways that have design traffic greater than 400 vehicles per day and an anticipated posted speed limit greater than 50 mph. See [~~http~~://www.modot.org/~~business~~/~~standards_and_specs/documents/20320.pdf~~ Standard Plan 203.20] for the maximum curve radius for use with spiral curve transitions. The length of spiral is the same as the length of superelevation and widening transition given in [~~http~~://www.modot.org/~~business/standards_and_specs~~/~~documents/20322.pdf~~ Standard Plan 203.22].		Spiral curves are used on all roadways that have design traffic greater than 400 vehicles per day and an anticipated posted speed limit greater than 50 mph. See [https://www.modot.org/media/16812 Standard Plan 203.20] for the maximum curve radius for use with spiral curve transitions. The length of spiral is the same as the length of superelevation and widening transition given in [https://www.modot.org/media/16819 Standard Plan 203.22].

	==230.1.6 Sight Distance==		==230.1.6 Sight Distance==

EPGsysop: /* 230.1.5 Spiral Transition Curves */ Per DE, clarified spiral transition curves guidance and bring them into compliance with standard plans

2017-08-03T13:52:32Z

230.1.5 Spiral Transition Curves: Per DE, clarified spiral transition curves guidance and bring them into compliance with standard plans

← Older revision		Revision as of 08:52, 3 August 2017
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	==230.1.5 Spiral Transition Curves==		==230.1.5 Spiral Transition Curves==

	Spiral curves are used on all roadways that have design traffic greater than 400 vehicles per day, anticipated posted speed greater than 50 mph ~~and a~~ curve radius ~~that is less than 2865 feet~~. The length of spiral is the same as the length of superelevation and widening transition given in ~~the standard plans~~.		Spiral curves are used on all roadways that have design traffic greater than 400 vehicles per day and an anticipated posted speed limit greater than 50 mph. See [http://www.modot.org/business/standards_and_specs/documents/20320.pdf Standard Plan 203.20] for the maximum curve radius for use with spiral curve transitions. The length of spiral is the same as the length of superelevation and widening transition given in [http://www.modot.org/business/standards_and_specs/documents/20322.pdf Standard Plan 203.22].

	==230.1.6 Sight Distance==		==230.1.6 Sight Distance==

Smithk: updated link

2014-12-08T19:59:18Z

updated link

← Older revision		Revision as of 14:59, 8 December 2014
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	==230.1.7 Bridge Considerations==		==230.1.7 Bridge Considerations==

	It is desirable to avoid vertical and horizontal curves on bridges. When a horizontal curve is unavoidable on a bridge, spirals and [[~~748.7~~ Bridge Reports and Layouts#~~748.7.4.4~~ Grades\|minimum horizontal clearance]] will be maintained between the roadway and the bridge separation structure.		It is desirable to avoid vertical and horizontal curves on bridges. When a horizontal curve is unavoidable on a bridge, spirals and [[:Category:747 Bridge Reports and Layouts#Grades\|minimum horizontal clearance]] will be maintained between the roadway and the bridge separation structure.

	==230.1.8 Curve Data on the Plans==		==230.1.8 Curve Data on the Plans==

Smithk: updated file types

2013-01-04T19:38:25Z

updated file types

← Older revision		Revision as of 14:38, 4 January 2013
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	\|[[Media:Green Book Fig 3-22b.pdf\|'''Green Book Figure 3-22b''' "Design Controls for Stopping Sight Distance on Horizontal Curves" ]]		\|[[Media:Green Book Fig 3-22b.pdf\|'''Green Book Figure 3-22b''' "Design Controls for Stopping Sight Distance on Horizontal Curves" ]]
	\|-		\|-
	\|[[media:Green Book Fig 3-23.~~jpg~~\|'''Green Book Figure 3-23''' "Diagram Illustrating Components for Horizontal Sight Distance"]]		\|[[media:Green Book Fig 3-23.pdf\|'''Green Book Figure 3-23''' "Diagram Illustrating Components for Horizontal Sight Distance"]]
	\|-		\|-
	\|[http://www.modot.mo.gov/business/standards_and_specs/documents/20320.pdf Standard Plan 203.20]		\|[http://www.modot.mo.gov/business/standards_and_specs/documents/20320.pdf Standard Plan 203.20]
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	==230.1.6 Sight Distance==		==230.1.6 Sight Distance==

	[[Media:Green Book Fig 3-22b.pdf\|Figures 3-22b]] and [[media:Green Book Fig 3-23.~~jpg~~\|3-23]] of the AASHTO Green Book (a graph diagram and equations) are used to determine the curve radius required to provide necessary horizontal sight distance for stopping and/or passing on roadway improvement projects.		[[Media:Green Book Fig 3-22b.pdf\|Figures 3-22b]] and [[media:Green Book Fig 3-23.pdf\|3-23]] of the AASHTO Green Book (a graph diagram and equations) are used to determine the curve radius required to provide necessary horizontal sight distance for stopping and/or passing on roadway improvement projects.

	==230.1.7 Bridge Considerations==		==230.1.7 Bridge Considerations==

Smithk: updated file type

2013-01-04T19:23:39Z

updated file type

← Older revision		Revision as of 14:23, 4 January 2013
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	\|'''Figures'''		\|'''Figures'''
	\|-		\|-
	\|[[Media:Green Book Fig 3-22b.~~jpg~~\|'''Green Book Figure 3-22b''' "Design Controls for Stopping Sight Distance on Horizontal Curves" ]]		\|[[Media:Green Book Fig 3-22b.pdf\|'''Green Book Figure 3-22b''' "Design Controls for Stopping Sight Distance on Horizontal Curves" ]]
	\|-		\|-
	\|[[media:Green Book Fig 3-23.jpg\|'''Green Book Figure 3-23''' "Diagram Illustrating Components for Horizontal Sight Distance"]]		\|[[media:Green Book Fig 3-23.jpg\|'''Green Book Figure 3-23''' "Diagram Illustrating Components for Horizontal Sight Distance"]]
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	==230.1.6 Sight Distance==		==230.1.6 Sight Distance==

	[[Media:Green Book Fig 3-22b.~~jpg~~\|Figures 3-22b]] and [[media:Green Book Fig 3-23.jpg\|3-23]] of the AASHTO Green Book (a graph diagram and equations) are used to determine the curve radius required to provide necessary horizontal sight distance for stopping and/or passing on roadway improvement projects.		[[Media:Green Book Fig 3-22b.pdf\|Figures 3-22b]] and [[media:Green Book Fig 3-23.jpg\|3-23]] of the AASHTO Green Book (a graph diagram and equations) are used to determine the curve radius required to provide necessary horizontal sight distance for stopping and/or passing on roadway improvement projects.

	==230.1.7 Bridge Considerations==		==230.1.7 Bridge Considerations==

Smithk: Per Design, updated AASHTO figures

2013-01-04T19:20:58Z

Per Design, updated AASHTO figures

← Older revision		Revision as of 14:20, 4 January 2013
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	\|'''Figures'''		\|'''Figures'''
	\|-		\|-
	\|[[Media:~~Controls for Stopping Sight Distance 1~~.~~pdf~~\|'''Green Book ~~Exhibit~~ 3-53''' "Design Controls for Stopping Sight Distance on Horizontal Curves" ]]		\|[[Media:Green Book Fig 3-22b.jpg\|'''Green Book Figure 3-22b''' "Design Controls for Stopping Sight Distance on Horizontal Curves" ]]
	\|-		\|-
	\|[[~~Media~~:~~Diagram Illustrating Components for Horizontal Sight Dist.~~.~~pdf~~\|'''Green Book ~~Exibit~~ 3-54''' "Diagram Illustrating Components for Horizontal Sight Distance"]]		\|[[media:Green Book Fig 3-23.jpg\|'''Green Book Figure 3-23''' "Diagram Illustrating Components for Horizontal Sight Distance"]]
	\|-		\|-
	\|[http://www.modot.mo.gov/business/standards_and_specs/documents/20320.pdf Standard Plan 203.20]		\|[http://www.modot.mo.gov/business/standards_and_specs/documents/20320.pdf Standard Plan 203.20]
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	==230.1.6 Sight Distance==		==230.1.6 Sight Distance==

	[[Media:~~Controls for Stopping Sight Distance 1~~.~~pdf~~\|~~Exhibits~~ 3-53]] and [[~~Media~~:~~Diagram Illustrating Components for Horizontal Sight Dist.~~.~~pdf~~\|3-54]] of the AASHTO Green Book (a graph diagram and equations) are used to determine the curve radius required to provide necessary horizontal sight distance for stopping and/or passing on roadway improvement projects.		[[Media:Green Book Fig 3-22b.jpg\|Figures 3-22b]] and [[media:Green Book Fig 3-23.jpg\|3-23]] of the AASHTO Green Book (a graph diagram and equations) are used to determine the curve radius required to provide necessary horizontal sight distance for stopping and/or passing on roadway improvement projects.

	==230.1.7 Bridge Considerations==		==230.1.7 Bridge Considerations==

Smithk: article construction

2009-10-22T19:14:36Z

article construction

← Older revision		Revision as of 14:14, 22 October 2009
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			[[image:230.1.jpg\|left\|250px]]
	{\|style="padding: 0.3em; margin-left:15px; border: 2px solid #cccccc; text-align:center; font-size: 95%; background:#f5f5f5" width="160px" align="right"		{\|style="padding: 0.3em; margin-left:15px; border: 2px solid #cccccc; text-align:center; font-size: 95%; background:#f5f5f5" width="160px" align="right"
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	\|[http://www.modot.mo.gov/business/standards_and_specs/documents/20321.pdf Standard Plan 203.21]		\|[http://www.modot.mo.gov/business/standards_and_specs/documents/20321.pdf Standard Plan 203.21]
	\|-		\|-

	\|}		\|}


	~~==230.1.1 Introduction==~~
	The operational characteristics of a roadway are directly affected by the horizontal alignment. The designer must consider the roads terrain, traffic volume, expected capacity and LOS together with other safety factors in order to properly anticipate the posted speed. Highways will be designed according to their anticipated posted speed as opposed to an arbitrary design speed.		The operational characteristics of a roadway are directly affected by the horizontal alignment. The designer must consider the roads terrain, traffic volume, expected capacity and LOS together with other safety factors in order to properly anticipate the posted speed. Highways will be designed according to their anticipated posted speed as opposed to an arbitrary design speed.

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	Horizontal curves are used when tangent lines of the roadway intersect at an angle exceeding ten minutes (for roadways with fewer than 400 vehicles per day, curves are not required for intersection angles of 1 degree or less). The centerline of median is generally used as the survey base line for divided roadway improvements. When the median width exceeds 100 ft. or individual roadways are not parallel, consideration should be given to using the inside edge of each travelway for the survey baseline for each individual alignment. For undivided pavements, the survey base line is at the center of the travelway pavement. Existing centerlines are used where practicable.		Horizontal curves are used when tangent lines of the roadway intersect at an angle exceeding ten minutes (for roadways with fewer than 400 vehicles per day, curves are not required for intersection angles of 1 degree or less). The centerline of median is generally used as the survey base line for divided roadway improvements. When the median width exceeds 100 ft. or individual roadways are not parallel, consideration should be given to using the inside edge of each travelway for the survey baseline for each individual alignment. For undivided pavements, the survey base line is at the center of the travelway pavement. Existing centerlines are used where practicable.

	===230.1.1.1 English Definition===		==230.1.1 English Definition==

	Instead of degree of curve, all horizontal curve data is described by radius. The arc definition of curvature is used for new alignment. The chord definition is used only when an existing chord defined curve is utilized in the alignment. Identify a curve that is based on the chord definition by placing "(chord)" after the radius listed in the curve data on the plans.		Instead of degree of curve, all horizontal curve data is described by radius. The arc definition of curvature is used for new alignment. The chord definition is used only when an existing chord defined curve is utilized in the alignment. Identify a curve that is based on the chord definition by placing "(chord)" after the radius listed in the curve data on the plans.

	===230.1.1.2 Metric Definitions===		==230.1.2 Metric Definitions==

	When an existing curve, either arc or chord definition, is utilized in a metric alignment it will be soft converted using the U.S. Survey Foot (''U.S. survey foot factor is 0.304800609601219 meters per foot.'').		When an existing curve, either arc or chord definition, is utilized in a metric alignment it will be soft converted using the U.S. Survey Foot (''U.S. survey foot factor is 0.304800609601219 meters per foot.'').

	===230.1.1.3 Length of Curve===		==230.1.3 Length of Curve==

	For small deflection angles, curves will be sufficiently long to avoid the appearance of a kink. Curves will be at least 500 ft. in length for a central angle of 5° and increase 100 ft. for each 1° decrease in the central angle. For anticipated posted speeds of 60 mph or less, the minimum length of a curve is about 15 times the anticipated posted speed (mph).		For small deflection angles, curves will be sufficiently long to avoid the appearance of a kink. Curves will be at least 500 ft. in length for a central angle of 5° and increase 100 ft. for each 1° decrease in the central angle. For anticipated posted speeds of 60 mph or less, the minimum length of a curve is about 15 times the anticipated posted speed (mph).
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	For anticipated posted speeds greater than 60 mph, controlled access facilities that use flat curvature, a desirable length of curve is about 30 times the anticipated posted speed (mph).		For anticipated posted speeds greater than 60 mph, controlled access facilities that use flat curvature, a desirable length of curve is about 30 times the anticipated posted speed (mph).

	===230.1.1.4 Superelevation and Widening===		==230.1.4 Superelevation and Widening==

	Superelevation rate, widening, and length of transition for various design categories are given on [http://www.modot.mo.gov/business/standards_and_specs/documents/20320.pdf Standard Plan 203.20] and [http://www.modot.mo.gov/business/standards_and_specs/documents/20321.pdf Standard Plan 203.21]. For divided pavements with narrow medians of 16 ft. or less in width, the superelevation runoff length for undivided roadways is used. For multiple lane roadways, the superelevation runoff length is multiplied by the appropriate factor based on the number of lanes. In urban areas where roadways with more than four lanes intersect at grade, consideration is given to reducing the pavement cross slope to minimize the difference in elevation between the extreme edges of the travelways. The difference in the rate of cross slopes for adjacent lanes should not exceed 5%, or 0.05 ft./ft. When the plans utilize the data given on the standard plans, only the maximum rate of superelevation and the maximum widening are shown with the horizontal curve data on the plans. Complete details of the superelevation and widening transition must be given on the plans if the standard plans details are not used.		Superelevation rate, widening, and length of transition for various design categories are given on [http://www.modot.mo.gov/business/standards_and_specs/documents/20320.pdf Standard Plan 203.20] and [http://www.modot.mo.gov/business/standards_and_specs/documents/20321.pdf Standard Plan 203.21]. For divided pavements with narrow medians of 16 ft. or less in width, the superelevation runoff length for undivided roadways is used. For multiple lane roadways, the superelevation runoff length is multiplied by the appropriate factor based on the number of lanes. In urban areas where roadways with more than four lanes intersect at grade, consideration is given to reducing the pavement cross slope to minimize the difference in elevation between the extreme edges of the travelways. The difference in the rate of cross slopes for adjacent lanes should not exceed 5%, or 0.05 ft./ft. When the plans utilize the data given on the standard plans, only the maximum rate of superelevation and the maximum widening are shown with the horizontal curve data on the plans. Complete details of the superelevation and widening transition must be given on the plans if the standard plans details are not used.

	===230.1.1.5 Spiral Transition Curves===		==230.1.5 Spiral Transition Curves==

	Spiral curves are used on all roadways that have design traffic greater than 400 vehicles per day, anticipated posted speed greater than 50 mph and a curve radius that is less than 2865 feet. The length of spiral is the same as the length of superelevation and widening transition given in the standard plans.		Spiral curves are used on all roadways that have design traffic greater than 400 vehicles per day, anticipated posted speed greater than 50 mph and a curve radius that is less than 2865 feet. The length of spiral is the same as the length of superelevation and widening transition given in the standard plans.

	===230.1.1.6 Sight Distance===		==230.1.6 Sight Distance==

	[[Media:Controls for Stopping Sight Distance 1.pdf\|Exhibits 3-53]] and [[Media:Diagram Illustrating Components for Horizontal Sight Dist..pdf\|3-54]] of the AASHTO Green Book (a graph diagram and equations) are used to determine the curve radius required to provide necessary horizontal sight distance for stopping and/or passing on roadway improvement projects.		[[Media:Controls for Stopping Sight Distance 1.pdf\|Exhibits 3-53]] and [[Media:Diagram Illustrating Components for Horizontal Sight Dist..pdf\|3-54]] of the AASHTO Green Book (a graph diagram and equations) are used to determine the curve radius required to provide necessary horizontal sight distance for stopping and/or passing on roadway improvement projects.

	===230.1.1.7 Bridge Considerations===		==230.1.7 Bridge Considerations==

	It is desirable to avoid vertical and horizontal curves on bridges. When a horizontal curve is unavoidable on a bridge, spirals and [[748.7 Bridge Reports and Layouts#748.7.4.4 Grades\|minimum horizontal clearance]] will be maintained between the roadway and the bridge separation structure.		It is desirable to avoid vertical and horizontal curves on bridges. When a horizontal curve is unavoidable on a bridge, spirals and [[748.7 Bridge Reports and Layouts#748.7.4.4 Grades\|minimum horizontal clearance]] will be maintained between the roadway and the bridge separation structure.

	===230.1.1.8 Curve Data on the Plans===		==230.1.8 Curve Data on the Plans==

	Example plans are available to illustrate how required curve data are to be shown.		Example plans are available to illustrate how required curve data are to be shown.

	===230.1.1.9 Stationing for the Main Roadway===		==230.1.9 Stationing for the Main Roadway==

	Stationing for roadway improvement projects proceed from north to south or from west to east.		Stationing for roadway improvement projects proceed from north to south or from west to east.
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	If the project is an improvement of an existing route, the stationing of the existing route is used. The ends of the proposed improvement are tied to the existing route and equated when applicable.		If the project is an improvement of an existing route, the stationing of the existing route is used. The ends of the proposed improvement are tied to the existing route and equated when applicable.

	===230.1.1.10 Stationing for Crossroads===		==230.1.10 Stationing for Crossroads==

	Stationing of intersected roadway is based on the existing stationing, if it exists. For crossroads where there is no existing stationing, the stationing proceeds from the left side of the intersection to the right side. The stationing is chosen so a five-station increment occurs at the intersection with the main roadway (ie. 15+00.00).		Stationing of intersected roadway is based on the existing stationing, if it exists. For crossroads where there is no existing stationing, the stationing proceeds from the left side of the intersection to the right side. The stationing is chosen so a five-station increment occurs at the intersection with the main roadway (ie. 15+00.00).
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	A sufficient distance is allowed on the left side of an interchange to provide the proposed improvement without having to use negative stationing. The crossroad stationing is equated to the main roadway stationing at the point of intersection and the angle of intersection is indicated.		A sufficient distance is allowed on the left side of an interchange to provide the proposed improvement without having to use negative stationing. The crossroad stationing is equated to the main roadway stationing at the point of intersection and the angle of intersection is indicated.

	===230.1.1.11 Ramp Base Lines and Stationing===		==230.1.11 Ramp Base Lines and Stationing==

	The base line for a ramp is located along the right edge of the ramp travelway relative to the direction of traffic. The stationing is carried in the direction of traffic except for diamond interchange ramps. Diamond interchange ramps are stationed in the same direction as the main roadway stationing. Ramp base lines are equated to the main roadway or cross road at their termini.		The base line for a ramp is located along the right edge of the ramp travelway relative to the direction of traffic. The stationing is carried in the direction of traffic except for diamond interchange ramps. Diamond interchange ramps are stationed in the same direction as the main roadway stationing. Ramp base lines are equated to the main roadway or cross road at their termini.
	[[category:230 Alignment of the Roadway\|230.1]]		[[category:230 Alignment of the Roadway\|230.1]]