230.2 Vertical Alignment - Revision history

Hoskir: /* 230.2.7 Passing Sight Distance */ renamed table 3-4 to 3-3

2023-07-06T19:06:57Z

230.2.7 Passing Sight Distance: renamed table 3-4 to 3-3

← Older revision		Revision as of 14:06, 6 July 2023
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	* The distance traveled by the opposing vehicle for two-thirds of the time the passing vehicle occupies the left lane (see [[Media:Elements of Passing Sight Distance for Two-Lane Hwy.pdf\|Exhibit 3-4]] of the Green Book).		* The distance traveled by the opposing vehicle for two-thirds of the time the passing vehicle occupies the left lane (see [[Media:Elements of Passing Sight Distance for Two-Lane Hwy.pdf\|Exhibit 3-4]] of the Green Book).

	[[media:Green Book Table 3-3.pdf\|Table 3-4]] of the AASHTO Green Book can be used to determine passing sight distances for various speeds. These values are based on a 3.5 ft. height of eye and a 3.5 ft. height of object. [[230.1 Horizontal Alignment\|Horizontal alignment]] is also considered in determining the location, extent, and percentage of passing distances. If passing maneuvers are to be performed on upgrades under the same assumptions about the behavior of the passing and the passed vehicles, the passing sight distance should be greater than the derived design values. Specific adjustments for design use are not available; however, the designer should recognize the desirability of exceeding the values shown in Exhibit 3-7 where practicable.		[[media:Green Book Table 3-3.pdf\|Table 3-3]] of the AASHTO Green Book can be used to determine passing sight distances for various speeds. These values are based on a 3.5 ft. height of eye and a 3.5 ft. height of object. [[230.1 Horizontal Alignment\|Horizontal alignment]] is also considered in determining the location, extent, and percentage of passing distances. If passing maneuvers are to be performed on upgrades under the same assumptions about the behavior of the passing and the passed vehicles, the passing sight distance should be greater than the derived design values. Specific adjustments for design use are not available; however, the designer should recognize the desirability of exceeding the values shown in Exhibit 3-7 where practicable.

	Procedures in the Highway Capacity Manual indicate another criterion for passing sight distance design on two-lane roadways that are several miles in length. The available passing sight distance along this length can be summarized to show the percentage of length with greater-than-minimum passing sight distance. Analysis of capacity related to this percentage can indicate whether or not alignment and profile adjustments are needed to accommodate the design hourly volume (DHV). When roadway sight distances are analyzed over the whole range of lengths within which passing maneuvers are made, a new design criterion may be evaluated. Where high traffic volumes are expected on a roadway and a high [[902.12 Glossary#Level of Service (LOS)\|level of service]] is to be maintained, frequent of nearly continuous passing sight distances are to be provided.		Procedures in the Highway Capacity Manual indicate another criterion for passing sight distance design on two-lane roadways that are several miles in length. The available passing sight distance along this length can be summarized to show the percentage of length with greater-than-minimum passing sight distance. Analysis of capacity related to this percentage can indicate whether or not alignment and profile adjustments are needed to accommodate the design hourly volume (DHV). When roadway sight distances are analyzed over the whole range of lengths within which passing maneuvers are made, a new design criterion may be evaluated. Where high traffic volumes are expected on a roadway and a high [[902.12 Glossary#Level of Service (LOS)\|level of service]] is to be maintained, frequent of nearly continuous passing sight distances are to be provided.

Smithk at 18:52, 23 April 2021

2021-04-23T18:52:39Z

← Older revision		Revision as of 13:52, 23 April 2021
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	==230.2.11 Grades==		==230.2.11 Grades==

	The profile grade in a ~~flood plain~~ is established to keep the roadway’s shoulder a minimum of 1 ft. above [[748.6 High Water Surface Elevation#748.6.1 Design Flood Elevation\|Design Flood Elevation]]. This applies to all types of roadways. The stream gradient must be considered in establishing profile grades in ~~flood plains~~. The Bridge Division will determine the design flood elevation to be used in establishing the profile grade.		The profile grade in a floodplain is established to keep the roadway’s shoulder a minimum of 1 ft. above [[748.6 High Water Surface Elevation#748.6.1 Design Flood Elevation\|Design Flood Elevation]]. This applies to all types of roadways. The stream gradient must be considered in establishing profile grades in floodplains. The Bridge Division will determine the design flood elevation to be used in establishing the profile grade.

	==230.2.12 Ramps==		==230.2.12 Ramps==

EPGsysop at 18:50, 29 June 2017

2017-06-29T18:50:34Z

← Older revision		Revision as of 13:50, 29 June 2017
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	[[image:230.2.4.jpg\|right\|400px]]		[[image:230.2.4.jpg\|right\|400px]]

	Sight distance is the length of the roadway ahead that is visible to the driver. Sight distance is an element of design that affects the safe and efficient operation of a roadway and it is given careful consideration during the location study and preparation of the preliminary plan. Stopping sight distance, based on the anticipated posted speed, is the sum of the distance for braking reaction and the braking distance required for a driver to stop the vehicle after sighting an object on the roadway. Passing sight distance, based on the anticipated posted speed, is the minimum distance required to safely make a normal passing maneuver on two-lane roadways at passing speeds representative of nearly all drivers. Operational sight distance is a portion of the passing sight distance and is the minimum distance necessary for safe passing at the prevailing speed of traffic (85th percentile speed). Operational sight distance is used by the Traffic Division in establishing no passing zones by marking yellow lines on the roadways. Minimum design controls have been established for stopping and passing sight distances. Consideration for the design of a longer vertical curve to provide for operational sight distance is based on good engineering judgment and economy		Sight distance is the length of the roadway ahead that is visible to the driver. Sight distance is an element of design that affects the safe and efficient operation of a roadway and it is given careful consideration during the location study and preparation of the preliminary plan. Stopping sight distance, based on the anticipated posted speed, is the sum of the distance for braking reaction and the braking distance required for a driver to stop the vehicle after sighting an object on the roadway. Passing sight distance, based on the anticipated posted speed, is the minimum distance required to safely make a normal passing maneuver on two-lane roadways at passing speeds representative of nearly all drivers. Operational sight distance is a portion of the passing sight distance and is the minimum distance necessary for safe passing at the prevailing speed of traffic (85th percentile speed). Operational sight distance is used by the Highway Safety and Traffic Division in establishing no passing zones by marking yellow lines on the roadways. Minimum design controls have been established for stopping and passing sight distances. Consideration for the design of a longer vertical curve to provide for operational sight distance is based on good engineering judgment and economy

	==230.2.5 Stopping Sight Distance and K Factors==		==230.2.5 Stopping Sight Distance and K Factors==

Smithk: updated link

2014-12-08T19:57:22Z

updated link

← Older revision		Revision as of 14:57, 8 December 2014
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	It is desirable to avoid vertical and horizontal curves on bridges. When a horizontal curve is unavoidable on a bridge, spirals and superelevations are not to be placed on the bridge itself unless absolutely necessary. To facilitate drainage, it is preferable that level grades not be used on a bridge; however, if the bridge is on a level grade, the roadway profile grade is to be kept as level as possible for a distance of 50 ft. from the ends of the bridge at locations where the approaching roadway grade is below the bridge elevation. This will reduce the impact load on the bridge. Flat grades and sag curves can cause drainage problems on bridges, especially those over railroads or other roadways, and should be avoided. To avoid drainage problems, the low point of a sag curve will not be placed on the bridge unless absolutely necessary.		It is desirable to avoid vertical and horizontal curves on bridges. When a horizontal curve is unavoidable on a bridge, spirals and superelevations are not to be placed on the bridge itself unless absolutely necessary. To facilitate drainage, it is preferable that level grades not be used on a bridge; however, if the bridge is on a level grade, the roadway profile grade is to be kept as level as possible for a distance of 50 ft. from the ends of the bridge at locations where the approaching roadway grade is below the bridge elevation. This will reduce the impact load on the bridge. Flat grades and sag curves can cause drainage problems on bridges, especially those over railroads or other roadways, and should be avoided. To avoid drainage problems, the low point of a sag curve will not be placed on the bridge unless absolutely necessary.

	[[~~748.7~~ Bridge Reports and Layouts#~~748.7.4.4~~ Grades\|Minimum vertical clearances over roadways]] will be maintained. The Design Division must approve use of a reduction of vertical clearance below the minimum, as a [[131.1 Design Exception Process\|design exception]]. Once approved, the project manager will notify the District Construction and Materials engineer to ensure measurement and posting of the final vertical clearance is accomplished.		[[:Category:747 Bridge Reports and Layouts#Grades\|Minimum vertical clearances over roadways]] will be maintained. The Design Division must approve use of a reduction of vertical clearance below the minimum, as a [[131.1 Design Exception Process\|design exception]]. Once approved, the project manager will notify the District Construction and Materials engineer to ensure measurement and posting of the final vertical clearance is accomplished.

	==230.2.11 Grades==		==230.2.11 Grades==

Smithk: /* 230.2.11 Grades */ Per Bridge, updated link

2014-12-05T14:54:39Z

230.2.11 Grades: Per Bridge, updated link

← Older revision		Revision as of 09:54, 5 December 2014
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	==230.2.11 Grades==		==230.2.11 Grades==

	The profile grade in a flood plain is established to keep the roadway’s shoulder a minimum of 1 ft. above ~~design high water~~. This applies to all types of roadways. The stream gradient must be considered in establishing profile grades in flood plains. The Bridge Division will determine the design ~~high water~~ elevation to be used in establishing the profile grade.		The profile grade in a flood plain is established to keep the roadway’s shoulder a minimum of 1 ft. above [[748.6 High Water Surface Elevation#748.6.1 Design Flood Elevation\|Design Flood Elevation]]. This applies to all types of roadways. The stream gradient must be considered in establishing profile grades in flood plains. The Bridge Division will determine the design flood elevation to be used in establishing the profile grade.

	==230.2.12 Ramps==		==230.2.12 Ramps==

Smithk at 14:16, 25 March 2014

2014-03-25T14:16:20Z

← Older revision		Revision as of 09:16, 25 March 2014
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	{\|style="padding: 0.3em; margin-left:15px; border: 1px solid #cccccc; text-align:center; font-size: 95%; background:#f5f5f5" width="~~160px~~" align="right"		{\|style="padding: 0.3em; margin-left:15px; border: 1px solid #cccccc; text-align:center; font-size: 95%; background:#f5f5f5" width="240px" align="right"
	\|-		\|-
	\|\|'''Figures'''		\|\|'''Figures'''

Smithk: Added AASHTO's Table 3-34 for crest vertical curves

2014-03-25T14:15:11Z

Added AASHTO's Table 3-34 for crest vertical curves

← Older revision		Revision as of 09:15, 25 March 2014
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	\|[[media:Green Book Fig 3-44.pdf\|'''Green Book Figure 3-44''' "Design Controls for Sag Vertical Curves-Open Road Conditions"]]		\|[[media:Green Book Fig 3-44.pdf\|'''Green Book Figure 3-44''' "Design Controls for Sag Vertical Curves-Open Road Conditions"]]
			\|-
			\|[[media:Green Book Table 3-34.pdf\|'''Green Book Table 3-34''' "Design Controls for Crest Vertical Curves"]]
	\|-		\|-
	\|[[media:Green Book Table 3-36.pdf\|'''Green Book Table 3-36''' "Design Controls for Sag Vertical Curves"]]		\|[[media:Green Book Table 3-36.pdf\|'''Green Book Table 3-36''' "Design Controls for Sag Vertical Curves"]]
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	==230.2.5 Stopping Sight Distance and K Factors==		==230.2.5 Stopping Sight Distance and K Factors==

	The minimum stopping sight distances and “K” factors for various anticipated operating speeds are given in the Green Book. These controls are based on a 3.5 ft. height of eye and a 2.0 ft. height of object. The “K” factors are approximate only and are used as a guide in determining the length of the vertical curve. K values are a measure of passenger comfort. Use of small K values is not recommended. The stopping sight distance, as determined by formula, is used as the final control. Where practical, vertical curves at least 300 ft. in length are used. [[media:Green Book Table 3-36.pdf\|Table 3-36]] of the AASHTO Greenbook is used to determine the length of a vertical curve required for any SSD based on change in grade.		The minimum stopping sight distances and “K” factors for various anticipated operating speeds are given in the Green Book. These controls are based on a 3.5 ft. height of eye and a 2.0 ft. height of object. The “K” factors are approximate only and are used as a guide in determining the length of the vertical curve. K values are a measure of passenger comfort. Use of small K values is not recommended. The stopping sight distance, as determined by formula, is used as the final control. Where practical, vertical curves at least 300 ft. in length are used. [[media:Green Book Table 3-36.pdf\|Table 3-36]] of the AASHTO Greenbook is used to determine the length of a sag vertical curve required for any SSD based on change in grade. [[media:Green Book Table 3-34.pdf\|Table 3-34]] of the AASHTO Greenbook is used to determine the length of a crest vertical curve required for any SSD based on change in grade.

	==230.2.6 Decision Sight Distance==		==230.2.6 Decision Sight Distance==

Smithk: /* 230.2.4 Sight Distance */ new photo

2013-10-21T14:53:34Z

230.2.4 Sight Distance: new photo

← Older revision		Revision as of 09:53, 21 October 2013
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	==230.2.4 Sight Distance==		==230.2.4 Sight Distance==
			[[image:230.2.4.jpg\|right\|400px]]

	Sight distance is the length of the roadway ahead that is visible to the driver. Sight distance is an element of design that affects the safe and efficient operation of a roadway and it is given careful consideration during the location study and preparation of the preliminary plan. Stopping sight distance, based on the anticipated posted speed, is the sum of the distance for braking reaction and the braking distance required for a driver to stop the vehicle after sighting an object on the roadway. Passing sight distance, based on the anticipated posted speed, is the minimum distance required to safely make a normal passing maneuver on two-lane roadways at passing speeds representative of nearly all drivers. Operational sight distance is a portion of the passing sight distance and is the minimum distance necessary for safe passing at the prevailing speed of traffic (85th percentile speed). Operational sight distance is used by the Traffic Division in establishing no passing zones by marking yellow lines on the roadways. Minimum design controls have been established for stopping and passing sight distances. Consideration for the design of a longer vertical curve to provide for operational sight distance is based on good engineering judgment and economy		Sight distance is the length of the roadway ahead that is visible to the driver. Sight distance is an element of design that affects the safe and efficient operation of a roadway and it is given careful consideration during the location study and preparation of the preliminary plan. Stopping sight distance, based on the anticipated posted speed, is the sum of the distance for braking reaction and the braking distance required for a driver to stop the vehicle after sighting an object on the roadway. Passing sight distance, based on the anticipated posted speed, is the minimum distance required to safely make a normal passing maneuver on two-lane roadways at passing speeds representative of nearly all drivers. Operational sight distance is a portion of the passing sight distance and is the minimum distance necessary for safe passing at the prevailing speed of traffic (85th percentile speed). Operational sight distance is used by the Traffic Division in establishing no passing zones by marking yellow lines on the roadways. Minimum design controls have been established for stopping and passing sight distances. Consideration for the design of a longer vertical curve to provide for operational sight distance is based on good engineering judgment and economy

Smithk: Per Design, removed archaic 2004 Green Book Exhibit 3-4 Passing Sight Distance for Design of Two-Lane Highways

2013-01-07T15:48:05Z

Per Design, removed archaic 2004 Green Book Exhibit 3-4 Passing Sight Distance for Design of Two-Lane Highways

← Older revision		Revision as of 10:48, 7 January 2013
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	\|[[media:Green Book Table 3-3.pdf\|'''Green Book Table 3-3''' "Decision Sight Distance"]]		\|[[media:Green Book Table 3-3.pdf\|'''Green Book Table 3-3''' "Decision Sight Distance"]]
	\|-
	~~\|[[Media:Elements of Passing Sight Distance for Two-Lane Hwy.pdf\|'''Green Book Exhibit 3-4''' "Elements of Passing Sight Distance for Two-Lane Highways"]]~~
	\|-		\|-
	\|[[media:Green Book Table 3-4.pdf\|'''Green Book Table 3-4''' "Passing Sight Distance for Design of Two-Lane Highways"]]		\|[[media:Green Book Table 3-4.pdf\|'''Green Book Table 3-4''' "Passing Sight Distance for Design of Two-Lane Highways"]]

Smithk: updated file types

2013-01-04T19:35:56Z

updated file types

← Older revision		Revision as of 14:06, 6 July 2023
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	* The distance traveled by the opposing vehicle for two-thirds of the time the passing vehicle occupies the left lane (see [[Media:Elements of Passing Sight Distance for Two-Lane Hwy.pdf\|Exhibit 3-4]] of the Green Book).		* The distance traveled by the opposing vehicle for two-thirds of the time the passing vehicle occupies the left lane (see [[Media:Elements of Passing Sight Distance for Two-Lane Hwy.pdf\|Exhibit 3-4]] of the Green Book).

	[[media:Green Book Table 3-3.pdf\|Table 3-4]] of the AASHTO Green Book can be used to determine passing sight distances for various speeds. These values are based on a 3.5 ft. height of eye and a 3.5 ft. height of object. [[230.1 Horizontal Alignment\|Horizontal alignment]] is also considered in determining the location, extent, and percentage of passing distances. If passing maneuvers are to be performed on upgrades under the same assumptions about the behavior of the passing and the passed vehicles, the passing sight distance should be greater than the derived design values. Specific adjustments for design use are not available; however, the designer should recognize the desirability of exceeding the values shown in Exhibit 3-7 where practicable.		[[media:Green Book Table 3-3.pdf\|Table 3-3]] of the AASHTO Green Book can be used to determine passing sight distances for various speeds. These values are based on a 3.5 ft. height of eye and a 3.5 ft. height of object. [[230.1 Horizontal Alignment\|Horizontal alignment]] is also considered in determining the location, extent, and percentage of passing distances. If passing maneuvers are to be performed on upgrades under the same assumptions about the behavior of the passing and the passed vehicles, the passing sight distance should be greater than the derived design values. Specific adjustments for design use are not available; however, the designer should recognize the desirability of exceeding the values shown in Exhibit 3-7 where practicable.

	Procedures in the Highway Capacity Manual indicate another criterion for passing sight distance design on two-lane roadways that are several miles in length. The available passing sight distance along this length can be summarized to show the percentage of length with greater-than-minimum passing sight distance. Analysis of capacity related to this percentage can indicate whether or not alignment and profile adjustments are needed to accommodate the design hourly volume (DHV). When roadway sight distances are analyzed over the whole range of lengths within which passing maneuvers are made, a new design criterion may be evaluated. Where high traffic volumes are expected on a roadway and a high [[902.12 Glossary#Level of Service (LOS)\|level of service]] is to be maintained, frequent of nearly continuous passing sight distances are to be provided.		Procedures in the Highway Capacity Manual indicate another criterion for passing sight distance design on two-lane roadways that are several miles in length. The available passing sight distance along this length can be summarized to show the percentage of length with greater-than-minimum passing sight distance. Analysis of capacity related to this percentage can indicate whether or not alignment and profile adjustments are needed to accommodate the design hourly volume (DHV). When roadway sight distances are analyzed over the whole range of lengths within which passing maneuvers are made, a new design criterion may be evaluated. Where high traffic volumes are expected on a roadway and a high [[902.12 Glossary#Level of Service (LOS)\|level of service]] is to be maintained, frequent of nearly continuous passing sight distances are to be provided.

← Older revision		Revision as of 14:35, 4 January 2013
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	\|\|'''Figures'''		\|\|'''Figures'''
	\|-		\|-
	\|[[media:Green Book Table 3-3.~~jpg~~\|'''Green Book Table 3-3''' "Decision Sight Distance"]]		\|[[media:Green Book Table 3-3.pdf\|'''Green Book Table 3-3''' "Decision Sight Distance"]]
	\|-		\|-
	\|[[Media:Elements of Passing Sight Distance for Two-Lane Hwy.pdf\|'''Green Book Exhibit 3-4''' "Elements of Passing Sight Distance for Two-Lane Highways"]]		\|[[Media:Elements of Passing Sight Distance for Two-Lane Hwy.pdf\|'''Green Book Exhibit 3-4''' "Elements of Passing Sight Distance for Two-Lane Highways"]]
	\|-		\|-
	\|[[media:Green Book Table 3-4.~~jpg~~\|'''Green Book Table 3-4''' "Passing Sight Distance for Design of Two-Lane Highways"]]		\|[[media:Green Book Table 3-4.pdf\|'''Green Book Table 3-4''' "Passing Sight Distance for Design of Two-Lane Highways"]]
	\|-		\|-
	\|[[media:Green Book Fig 3-44.pdf\|'''Green Book Figure 3-44''' "Design Controls for Sag Vertical Curves-Open Road Conditions"]]		\|[[media:Green Book Fig 3-44.pdf\|'''Green Book Figure 3-44''' "Design Controls for Sag Vertical Curves-Open Road Conditions"]]
	\|-		\|-
	\|[[media:Green Book Table 3-36.~~jpg~~\|'''Green Book Table 3-36''' "Design Controls for Sag Vertical Curves"]]		\|[[media:Green Book Table 3-36.pdf\|'''Green Book Table 3-36''' "Design Controls for Sag Vertical Curves"]]
	\|}		\|}

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	==230.2.5 Stopping Sight Distance and K Factors==		==230.2.5 Stopping Sight Distance and K Factors==

	The minimum stopping sight distances and “K” factors for various anticipated operating speeds are given in the Green Book. These controls are based on a 3.5 ft. height of eye and a 2.0 ft. height of object. The “K” factors are approximate only and are used as a guide in determining the length of the vertical curve. K values are a measure of passenger comfort. Use of small K values is not recommended. The stopping sight distance, as determined by formula, is used as the final control. Where practical, vertical curves at least 300 ft. in length are used. [[media:Green Book Table 3-36.~~jpg~~\|Table 3-36]] of the AASHTO Greenbook is used to determine the length of a vertical curve required for any SSD based on change in grade.		The minimum stopping sight distances and “K” factors for various anticipated operating speeds are given in the Green Book. These controls are based on a 3.5 ft. height of eye and a 2.0 ft. height of object. The “K” factors are approximate only and are used as a guide in determining the length of the vertical curve. K values are a measure of passenger comfort. Use of small K values is not recommended. The stopping sight distance, as determined by formula, is used as the final control. Where practical, vertical curves at least 300 ft. in length are used. [[media:Green Book Table 3-36.pdf\|Table 3-36]] of the AASHTO Greenbook is used to determine the length of a vertical curve required for any SSD based on change in grade.

	==230.2.6 Decision Sight Distance==		==230.2.6 Decision Sight Distance==

	Decision sight distance is used where the stopping sight distance is inadequate to allow a reasonably competent driver the distance to react to potentially hazardous situations. This condition may be present in a roadway environment that is cluttered visually, an intersection congested with traffic, a median crossover, or has an unusual roadway geometric configuration. In decision areas the decision sight distance gives a greater margin for error and provides the distance to maneuver a vehicle safely. See [[media:Green Book Table 3-3.~~jpg~~\|Table 3-3]] of the AASHTO Green Book for decision sight distance values.		Decision sight distance is used where the stopping sight distance is inadequate to allow a reasonably competent driver the distance to react to potentially hazardous situations. This condition may be present in a roadway environment that is cluttered visually, an intersection congested with traffic, a median crossover, or has an unusual roadway geometric configuration. In decision areas the decision sight distance gives a greater margin for error and provides the distance to maneuver a vehicle safely. See [[media:Green Book Table 3-3.pdf\|Table 3-3]] of the AASHTO Green Book for decision sight distance values.

	==230.2.7 Passing Sight Distance==		==230.2.7 Passing Sight Distance==
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	* The distance traveled by the opposing vehicle for two-thirds of the time the passing vehicle occupies the left lane (see [[Media:Elements of Passing Sight Distance for Two-Lane Hwy.pdf\|Exhibit 3-4]] of the Green Book).		* The distance traveled by the opposing vehicle for two-thirds of the time the passing vehicle occupies the left lane (see [[Media:Elements of Passing Sight Distance for Two-Lane Hwy.pdf\|Exhibit 3-4]] of the Green Book).

	[[media:Green Book Table 3-3.~~jpg~~\|Table 3-4]] of the AASHTO Green Book can be used to determine passing sight distances for various speeds. These values are based on a 3.5 ft. height of eye and a 3.5 ft. height of object. [[230.1 Horizontal Alignment\|Horizontal alignment]] is also considered in determining the location, extent, and percentage of passing distances. If passing maneuvers are to be performed on upgrades under the same assumptions about the behavior of the passing and the passed vehicles, the passing sight distance should be greater than the derived design values. Specific adjustments for design use are not available; however, the designer should recognize the desirability of exceeding the values shown in Exhibit 3-7 where practicable.		[[media:Green Book Table 3-3.pdf\|Table 3-4]] of the AASHTO Green Book can be used to determine passing sight distances for various speeds. These values are based on a 3.5 ft. height of eye and a 3.5 ft. height of object. [[230.1 Horizontal Alignment\|Horizontal alignment]] is also considered in determining the location, extent, and percentage of passing distances. If passing maneuvers are to be performed on upgrades under the same assumptions about the behavior of the passing and the passed vehicles, the passing sight distance should be greater than the derived design values. Specific adjustments for design use are not available; however, the designer should recognize the desirability of exceeding the values shown in Exhibit 3-7 where practicable.

	Procedures in the Highway Capacity Manual indicate another criterion for passing sight distance design on two-lane roadways that are several miles in length. The available passing sight distance along this length can be summarized to show the percentage of length with greater-than-minimum passing sight distance. Analysis of capacity related to this percentage can indicate whether or not alignment and profile adjustments are needed to accommodate the design hourly volume (DHV). When roadway sight distances are analyzed over the whole range of lengths within which passing maneuvers are made, a new design criterion may be evaluated. Where high traffic volumes are expected on a roadway and a high [[902.12 Glossary#Level of Service (LOS)\|level of service]] is to be maintained, frequent of nearly continuous passing sight distances are to be provided.		Procedures in the Highway Capacity Manual indicate another criterion for passing sight distance design on two-lane roadways that are several miles in length. The available passing sight distance along this length can be summarized to show the percentage of length with greater-than-minimum passing sight distance. Analysis of capacity related to this percentage can indicate whether or not alignment and profile adjustments are needed to accommodate the design hourly volume (DHV). When roadway sight distances are analyzed over the whole range of lengths within which passing maneuvers are made, a new design criterion may be evaluated. Where high traffic volumes are expected on a roadway and a high [[902.12 Glossary#Level of Service (LOS)\|level of service]] is to be maintained, frequent of nearly continuous passing sight distances are to be provided.
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	* General appearance		* General appearance

	The "K" factors shown in [[media:Green Book Fig 3-44.pdf\|Figure 3-44]] and [[media:Green Book Table 3-36.~~jpg~~\|Table 3-36]] of the Green Book are for the most part based upon headlight sight distance and are to be used in the design of sag vertical curves. Where practicable, vertical curves at least 300 ft. in length are used.		The "K" factors shown in [[media:Green Book Fig 3-44.pdf\|Figure 3-44]] and [[media:Green Book Table 3-36.pdf\|Table 3-36]] of the Green Book are for the most part based upon headlight sight distance and are to be used in the design of sag vertical curves. Where practicable, vertical curves at least 300 ft. in length are used.

	In some restrictive situations, the sag “K” factor determined above may be reduced to satisfy passenger comfort criteria. The length of vertical curves needed to satisfy the “comfort factor” at the posted speed is about 50 percent of that needed to satisfy the headlight sight distance criterion for the normal range of design conditions. The following formula (based on 3-51 of the Green Book) may be used to determine the length of the sag vertical curve for the reduced K factor.		In some restrictive situations, the sag “K” factor determined above may be reduced to satisfy passenger comfort criteria. The length of vertical curves needed to satisfy the “comfort factor” at the posted speed is about 50 percent of that needed to satisfy the headlight sight distance criterion for the normal range of design conditions. The following formula (based on 3-51 of the Green Book) may be used to determine the length of the sag vertical curve for the reduced K factor.