234.2 Diamond Interchanges - Revision history

Hoskir: /* 234.2.1.10 Grading */ changed GeoPak to OpenRoads Designer

2024-01-16T15:43:26Z

234.2.1.10 Grading: changed GeoPak to OpenRoads Designer

← Older revision		Revision as of 10:43, 16 January 2024
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	===234.2.1.10 Grading===		===234.2.1.10 Grading===

	MicroStation, ~~GEOPAK~~ or other computer programs or aids are used to compute grading quantities in interchange areas. The method used is dependent upon the type of interchange, the terrain, and other site-specific factors. Regardless of the method, the plans will include adequate cross sections or contours to determine the quantity of grading material within the interchange area.		MicroStation, OpenRoads Designer or other computer programs or aids are used to compute grading quantities in interchange areas. The method used is dependent upon the type of interchange, the terrain, and other site-specific factors. Regardless of the method, the plans will include adequate cross sections or contours to determine the quantity of grading material within the interchange area.

	===234.2.1.11 Site Grading===		===234.2.1.11 Site Grading===

Smithk: /* 234.2.1.10 Grading */ Per CADD, removed CADD links

2019-06-24T15:14:09Z

234.2.1.10 Grading: Per CADD, removed CADD links

← Older revision		Revision as of 10:14, 24 June 2019
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	===234.2.1.10 Grading===		===234.2.1.10 Grading===

	~~[http://caddnet/index.php?title=Category:~~MicroStation ~~MicroStation]~~, ~~[http://caddnet/index.php?title=Category:GEOPAK_Road~~ GEOPAK] or other computer programs or aids are used to compute grading quantities in interchange areas. The method used is dependent upon the type of interchange, the terrain, and other site-specific factors. Regardless of the method, the plans will include adequate cross sections or contours to determine the quantity of grading material within the interchange area.		MicroStation, GEOPAK or other computer programs or aids are used to compute grading quantities in interchange areas. The method used is dependent upon the type of interchange, the terrain, and other site-specific factors. Regardless of the method, the plans will include adequate cross sections or contours to determine the quantity of grading material within the interchange area.

	===234.2.1.11 Site Grading===		===234.2.1.11 Site Grading===

Smithk at 19:19, 28 September 2018

2018-09-28T19:19:45Z

← Older revision		Revision as of 14:19, 28 September 2018
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	Ramp base lines are always equated to the survey centerline and other ramp base line intersection points or the crossroad centerline intersection point. The equations include offsets and intersection angles.		Ramp base lines are always equated to the survey centerline and other ramp base line intersection points or the crossroad centerline intersection point. The equations include offsets and intersection angles.

	Interchange ramps are numbered for ease of identification. The width of each ramp should be as indicated on [~~http~~://www.modot.~~mo.gov/business/standards_and_specs~~/~~documents~~/~~20340.pdf~~ Standard Plan 203.40].		Interchange ramps are numbered for ease of identification. The width of each ramp should be as indicated on [https://www.modot.org/media/16821 Standard Plan 203.40].

	The district approves the [[Media:234.2.1.1 Diamond Interchange.pdf\|overall geometric layout of a diamond interchange'''<sup>1</sup>''']] (complete with [[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|ramp details]]) from the schematic drawing shown on the preliminary plan.		The district approves the [[Media:234.2.1.1 Diamond Interchange.pdf\|overall geometric layout of a diamond interchange'''<sup>1</sup>''']] (complete with [[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|ramp details]]) from the schematic drawing shown on the preliminary plan.

EPGsysop at 18:51, 29 June 2017

2017-06-29T18:51:42Z

← Older revision		Revision as of 13:51, 29 June 2017
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	===234.2.1.15 Signals===		===234.2.1.15 Signals===

	When warranted, the provision of traffic signals will be made early in the design process. Items to consider include lane assignments, signal visibility, pedestrian requirements and placement of the signal posts and bases. The preferred method of signal post design uses conventional single tubular steel posts, mast arm and bases as shown in the standard plans. This may be accomplished by using traffic islands, if necessary. All non-standard signal structures, shop drawings and stress calculations must be submitted to the Traffic Division for approval prior to fabrication. Detailed information is contained in [[:Category:902 Signals\|EPG 902 Signals]].		When warranted, the provision of traffic signals will be made early in the design process. Items to consider include lane assignments, signal visibility, pedestrian requirements and placement of the signal posts and bases. The preferred method of signal post design uses conventional single tubular steel posts, mast arm and bases as shown in the standard plans. This may be accomplished by using traffic islands, if necessary. All non-standard signal structures, shop drawings and stress calculations must be submitted to the Highway Safety and Traffic Division for approval prior to fabrication. Detailed information is contained in [[:Category:902 Signals\|EPG 902 Signals]].

	===234.2.1.16 Lighting, Signing and Pavement Marking===		===234.2.1.16 Lighting, Signing and Pavement Marking===

Smithk: /* 234.2.1.1 Ramp and Preliminary Plan Criteria */ added clarifying note

2015-07-31T14:47:22Z

234.2.1.1 Ramp and Preliminary Plan Criteria: added clarifying note

← Older revision		Revision as of 09:47, 31 July 2015
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	Interchange ramps are numbered for ease of identification. The width of each ramp should be as indicated on [http://www.modot.mo.gov/business/standards_and_specs/documents/20340.pdf Standard Plan 203.40].		Interchange ramps are numbered for ease of identification. The width of each ramp should be as indicated on [http://www.modot.mo.gov/business/standards_and_specs/documents/20340.pdf Standard Plan 203.40].

	The district approves the [[Media:234.2.1.1 Diamond Interchange.pdf\|overall geometric layout of a diamond interchange]] (complete with [[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|ramp details]]) from the schematic drawing shown on the preliminary plan.		The district approves the [[Media:234.2.1.1 Diamond Interchange.pdf\|overall geometric layout of a diamond interchange'''<sup>1</sup>''']] (complete with [[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|ramp details]]) from the schematic drawing shown on the preliminary plan.

	Drawings with detail interchange geometrics are developed to the same scale used on the plans and on standard size, 22 in. x 34 in. sheets. The drawing includes complete alignment details for ramp base lines and shows the limits of pavement. A supplemental standard size full profile sheet or cross section sheet is used for plotting profiles and developing ramp grades. The profile is plotted to the horizontal scale used on the plans, and to a vertical scale of 1 in.=10 ft. (1:100). If a standard size sheet is too small, additional standard size sheets are used, with match lines, or the layout may be prepared on a sheet of multiples of the standard size. The plan is developed to the best possible accuracy since this sheet becomes the base for later drawings (i.e. for grade separation reports). Grades are considered tentative at this stage and are developed in a similar manner to the preliminary plans. The plan sheet(s) includes complete traffic data for the interchange, including all turning movements. The traffic data is shown with the design hourly volume (DHV) over average annual daily traffic (AADT) and also the percent of trucks.		Drawings with detail interchange geometrics are developed to the same scale used on the plans and on standard size, 22 in. x 34 in. sheets. The drawing includes complete alignment details for ramp base lines and shows the limits of pavement. A supplemental standard size full profile sheet or cross section sheet is used for plotting profiles and developing ramp grades. The profile is plotted to the horizontal scale used on the plans, and to a vertical scale of 1 in.=10 ft. (1:100). If a standard size sheet is too small, additional standard size sheets are used, with match lines, or the layout may be prepared on a sheet of multiples of the standard size. The plan is developed to the best possible accuracy since this sheet becomes the base for later drawings (i.e. for grade separation reports). Grades are considered tentative at this stage and are developed in a similar manner to the preliminary plans. The plan sheet(s) includes complete traffic data for the interchange, including all turning movements. The traffic data is shown with the design hourly volume (DHV) over average annual daily traffic (AADT) and also the percent of trucks.
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	[[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|Alignment controls]] for diamond interchanges are available. The ramp curvature at the ramp nose or gore area will have a minimum radius of 6 degrees or less. The delta for this curve will be as small as the ramp grade and location of the ramp terminal at the crossroad will permit. If practicable, the ramp curvature is established so both ends of the curve are at least 100 ft. from the ramp nose measured along the ramp base line.		[[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|Alignment controls]] for diamond interchanges are available. The ramp curvature at the ramp nose or gore area will have a minimum radius of 6 degrees or less. The delta for this curve will be as small as the ramp grade and location of the ramp terminal at the crossroad will permit. If practicable, the ramp curvature is established so both ends of the curve are at least 100 ft. from the ramp nose measured along the ramp base line.

			:'''<sup>1</sup>''' This diagram presents a conventional diamond interchange and its associated 800 ft. dimension between ramp termini. The designer is encouraged to consider a shorter dimension between ramp termini if tight urban conditions, for example, exist.

	===234.2.1.2 Basic Number of Lanes===		===234.2.1.2 Basic Number of Lanes===

Smithk: Per Design, updated 700' dimension between ramp termini in the conventional diamond to 800' to reflect FHWA guidance

2015-07-31T14:30:20Z

Per Design, updated 700' dimension between ramp termini in the conventional diamond to 800' to reflect FHWA guidance

← Older revision		Revision as of 09:30, 31 July 2015
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	[[image:234.2.1.jpg\|~~left~~\|350px]]		[[image:234.2.1.jpg\|right\|350px]]
	{\|style="padding: 0.3em; margin-~~left~~:~~15px~~; border:1px solid #a9a9a9; text-align:center; font-size: 95%; background:#f5f5f5" width="~~200px~~" align="~~right~~"		{\|style="padding: 0.3em; margin-right:10px; border:1px solid #a9a9a9; text-align:center; font-size: 95%; background:#f5f5f5" width="300px" align="left"
	\|-		\|-
	\|'''Figures'''		\|'''Figures'''
	\|-		\|-
	\|[[Media:~~236~~.~~13 Fig1 Access Control at~~ Diamond ~~Interc hangers~~.pdf\|Geometric Layout of a Diamond Interchange]]		\|[[Media:234.2.1.1 Diamond Interchange.pdf\|Geometric Layout of a Diamond Interchange]]'''*'''
			\|-
			\|'''*''' This diagram presents a conventional diamond interchange and its associated 800 ft. dimension between ramp termini. The designer is encouraged to consider a shorter dimension between ramp termini if tight urban conditions, for example, exist.
	\|-		\|-
	\|[[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|Ramp Layout Details of a Diamond Interchange]]		\|[[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|Ramp Layout Details of a Diamond Interchange]]
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			==234.2.1 Introduction==

			'''Advantages'''

	==~~234~~.2.~~1 Introduction~~==		'''<font color="blue">▪</font color="blue">''' Most common interchange configuration; therefore, it meets driver expectation.

			'''<font color="blue">▪</font color="blue">''' Well suited for both rural and urban use.

			'''<font color="blue">▪</font color="blue">''' Adaptable in major-minor road crossings where grade crossings on the minor roadway can be handled with minimal interference to traffic approaching the intersection from any direction.

	'''~~Advantages~~'''		'''<font color="blue">▪</font color="blue">''' Lower cost than other interchange configurations.

	* Most common interchange configuration; therefore, it meets driver expectation.		'''<font color="blue">▪</font color="blue">''' Requires less right of way than other types of interchanges.
	* Well suited for both rural and urban use.
	* Adaptable in major-minor road crossings where grade crossings on the minor roadway can be handled with minimal interference to traffic approaching the intersection from any direction.
	* Lower cost than other interchange configurations.
	* Requires less right of way than other types of interchanges.

	'''Disadvantages'''		'''Disadvantages'''

	* Possible wrong-way entry on the ramps from the crossroad must be addressed.		'''<font color="blue">▪</font color="blue">''' Possible wrong-way entry on the ramps from the crossroad must be addressed.
	* The greatest impediment to smooth operation is the left-turning traffic at the crossroad intersections.
	* Level of service decreases as the volume of traffic on the crossroad becomes heavy.		'''<font color="blue">▪</font color="blue">''' The greatest impediment to smooth operation is the left-turning traffic at the crossroad intersections.

			'''<font color="blue">▪</font color="blue">''' Level of service decreases as the volume of traffic on the crossroad becomes heavy.

	The simplest and perhaps the most common interchange configuration is the diamond. A full diamond interchange is formed when a one-way diagonal ramp is provided in each quadrant of the interchange. The ramps are aligned with free-flow from the main roadway and an intersection on the crossroad. Diamond interchanges have application in both rural and urban areas. They are particularly adaptable to major-minor crossings where left turns at grade on the minor roadway can be handled with minimal interference to traffic approaching the intersection from either direction. The intersection on the crossroad formed by the ramp terminal functions as a T-type intersection and is designed according to the direction outlined in [[:category:233 At - Grade Intersections\|At-Grade Intersections]]. However, because these intersections really do have four legs, two of which are one-way, they present a problem in traffic control to prevent wrong-way entry from the crossroad. For this reason, a median can be provided on the crossroad to facilitate proper channelization of traffic. This median can be either painted or raised. Additional [[:category:903 Highway Signing\|signing]] is helpful to prevent improper use of the ramps.		The simplest and perhaps the most common interchange configuration is the diamond. A full diamond interchange is formed when a one-way diagonal ramp is provided in each quadrant of the interchange. The ramps are aligned with free-flow from the main roadway and an intersection on the crossroad. Diamond interchanges have application in both rural and urban areas. They are particularly adaptable to major-minor crossings where left turns at grade on the minor roadway can be handled with minimal interference to traffic approaching the intersection from either direction. The intersection on the crossroad formed by the ramp terminal functions as a T-type intersection and is designed according to the direction outlined in [[:category:233 At - Grade Intersections\|At-Grade Intersections]]. However, because these intersections really do have four legs, two of which are one-way, they present a problem in traffic control to prevent wrong-way entry from the crossroad. For this reason, a median can be provided on the crossroad to facilitate proper channelization of traffic. This median can be either painted or raised. Additional [[:category:903 Highway Signing\|signing]] is helpful to prevent improper use of the ramps.
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	Interchange ramps are numbered for ease of identification. The width of each ramp should be as indicated on [http://www.modot.mo.gov/business/standards_and_specs/documents/20340.pdf Standard Plan 203.40].		Interchange ramps are numbered for ease of identification. The width of each ramp should be as indicated on [http://www.modot.mo.gov/business/standards_and_specs/documents/20340.pdf Standard Plan 203.40].

	The district approves the [[Media:~~236~~.~~13 Fig1 Access Control at~~ Diamond ~~Interc hangers~~.pdf\|overall geometric layout of a diamond interchange]] (complete with [[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|ramp details]]) from the schematic drawing shown on the preliminary plan.		The district approves the [[Media:234.2.1.1 Diamond Interchange.pdf\|overall geometric layout of a diamond interchange]] (complete with [[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|ramp details]]) from the schematic drawing shown on the preliminary plan.

	Drawings with detail interchange geometrics are developed to the same scale used on the plans and on standard size, 22 in. x 34 in. sheets. The drawing includes complete alignment details for ramp base lines and shows the limits of pavement. A supplemental standard size full profile sheet or cross section sheet is used for plotting profiles and developing ramp grades. The profile is plotted to the horizontal scale used on the plans, and to a vertical scale of 1 in.=10 ft. (1:100). If a standard size sheet is too small, additional standard size sheets are used, with match lines, or the layout may be prepared on a sheet of multiples of the standard size. The plan is developed to the best possible accuracy since this sheet becomes the base for later drawings (i.e. for grade separation reports). Grades are considered tentative at this stage and are developed in a similar manner to the preliminary plans. The plan sheet(s) includes complete traffic data for the interchange, including all turning movements. The traffic data is shown with the design hourly volume (DHV) over average annual daily traffic (AADT) and also the percent of trucks.		Drawings with detail interchange geometrics are developed to the same scale used on the plans and on standard size, 22 in. x 34 in. sheets. The drawing includes complete alignment details for ramp base lines and shows the limits of pavement. A supplemental standard size full profile sheet or cross section sheet is used for plotting profiles and developing ramp grades. The profile is plotted to the horizontal scale used on the plans, and to a vertical scale of 1 in.=10 ft. (1:100). If a standard size sheet is too small, additional standard size sheets are used, with match lines, or the layout may be prepared on a sheet of multiples of the standard size. The plan is developed to the best possible accuracy since this sheet becomes the base for later drawings (i.e. for grade separation reports). Grades are considered tentative at this stage and are developed in a similar manner to the preliminary plans. The plan sheet(s) includes complete traffic data for the interchange, including all turning movements. The traffic data is shown with the design hourly volume (DHV) over average annual daily traffic (AADT) and also the percent of trucks.

Smithk: /* 234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type) */ minor correction

2015-05-05T15:21:12Z

234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type): minor correction

← Older revision		Revision as of 10:21, 5 May 2015
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	===234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type)===		===234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type)===

	Minimum speed change lengths are given in [[media:Green Book Table 10-3.pdf\|Tables 10-3]] and [[media:Green Book Table 10-5.pdf\|10-5]] of the AASHTO Green Book. Lengths shown in these tables are for grades of 2% or less on the speed change lane. [[media:Green Book Table 10-4.pdf\|Table 10-4]] of the AASHTO Green Book provides adjustment to these lengths for grades over 2%. Speed change lanes are provided at all ramp entrances and exits where the number of through traffic lanes each side of the ramp terminal are equal. The combined length of full width acceleration lane and taper will not be less than 600 ft. A shoulder, at least 6 ft. wide, is provided for auxiliary lanes along the through traffic lanes (except a 4-foot shoulder will be provided along a median acceleration lane). Auxiliary lane width is the same as the width provided for the through traffic lanes. In rural areas, the ramp nose will be visible to approaching traffic for a distance equal to at least 1.25 times the stopping sight distance on the freeway or expressway. When ~~Stoping sight distance~~ cannot be obtained in rural areas a [[Media:234.2 Figure 1 Diamond type Interchange Ramps.pdf\|deceleration lane]] length of 350 ft. is used.		Minimum speed change lengths are given in [[media:Green Book Table 10-3.pdf\|Tables 10-3]] and [[media:Green Book Table 10-5.pdf\|10-5]] of the AASHTO Green Book. Lengths shown in these tables are for grades of 2% or less on the speed change lane. [[media:Green Book Table 10-4.pdf\|Table 10-4]] of the AASHTO Green Book provides adjustment to these lengths for grades over 2%. Speed change lanes are provided at all ramp entrances and exits where the number of through traffic lanes each side of the ramp terminal are equal. The combined length of full width acceleration lane and taper will not be less than 600 ft. A shoulder, at least 6 ft. wide, is provided for auxiliary lanes along the through traffic lanes (except a 4-foot shoulder will be provided along a median acceleration lane). Auxiliary lane width is the same as the width provided for the through traffic lanes. In rural areas, the ramp nose will be visible to approaching traffic for a distance equal to at least 1.25 times the stopping sight distance on the freeway or expressway. When Stopping Sight Distance cannot be obtained in rural areas a [[Media:234.2 Figure 1 Diamond type Interchange Ramps.pdf\|deceleration lane]] length of 350 ft. is used.

	Where interchanges are closely spaced (e.g. less than 2500 ft.) the auxiliary lane for acceleration will be extended to the exit of the next interchange. An entrance lane followed by a lane exiting forms a traffic weaving section that requires added pavement width and length for weaving capacity. The capacity of the auxiliary lane connecting the on-ramp with the off-ramp will be determined using the Highway Capacity Manual or an appropriate traffic-modeling program (i.e. VISSIM). The weaving section will have a length and number of lanes based on the appropriate level of service outlined in the [[:category:232 Facility Selection\|Facility Selection]] article.		Where interchanges are closely spaced (e.g. less than 2500 ft.) the auxiliary lane for acceleration will be extended to the exit of the next interchange. An entrance lane followed by a lane exiting forms a traffic weaving section that requires added pavement width and length for weaving capacity. The capacity of the auxiliary lane connecting the on-ramp with the off-ramp will be determined using the Highway Capacity Manual or an appropriate traffic-modeling program (i.e. VISSIM). The weaving section will have a length and number of lanes based on the appropriate level of service outlined in the [[:category:232 Facility Selection\|Facility Selection]] article.

Smithk: /* 234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type) */ minor typo correction

2015-04-30T17:29:17Z

234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type): minor typo correction

← Older revision		Revision as of 12:29, 30 April 2015
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	===234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type)===		===234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type)===

	Minimum speed change lengths are given in [[media:Green Book Table 10-3.pdf\|Tables 10-3]] and [[media:Green Book Table 10-5.pdf\|10-5]] of the AASHTO Green Book. Lengths shown in these tables are for grades of 2% or less on the speed change lane. [[media:Green Book Table 10-4.pdf\|Table 10-4]] of the AASHTO Green Book provides adjustment to these lengths for grades over 2%. Speed change lanes are provided at all ramp entrances and exits where the number of through traffic lanes each side of the ramp terminal are equal. The combined length of full width acceleration lane and taper will not be less than 600 ft. A shoulder, at least 6 ft. wide, is provided for auxiliary lanes along the through traffic lanes (except a 4-foot shoulder will be provided along a median acceleration lane). Auxiliary lane width is the same as the width provided for the through traffic lanes. In rural areas, the ramp nose will be visible to approaching traffic for a distance equal to at least 1.25 times the stopping sight distance on the freeway of expressway. When Stoping sight distance cannot be obtained in rural areas a [[Media:234.2 Figure 1 Diamond type Interchange Ramps.pdf\|deceleration lane]] length of 350 ft. is used.		Minimum speed change lengths are given in [[media:Green Book Table 10-3.pdf\|Tables 10-3]] and [[media:Green Book Table 10-5.pdf\|10-5]] of the AASHTO Green Book. Lengths shown in these tables are for grades of 2% or less on the speed change lane. [[media:Green Book Table 10-4.pdf\|Table 10-4]] of the AASHTO Green Book provides adjustment to these lengths for grades over 2%. Speed change lanes are provided at all ramp entrances and exits where the number of through traffic lanes each side of the ramp terminal are equal. The combined length of full width acceleration lane and taper will not be less than 600 ft. A shoulder, at least 6 ft. wide, is provided for auxiliary lanes along the through traffic lanes (except a 4-foot shoulder will be provided along a median acceleration lane). Auxiliary lane width is the same as the width provided for the through traffic lanes. In rural areas, the ramp nose will be visible to approaching traffic for a distance equal to at least 1.25 times the stopping sight distance on the freeway or expressway. When Stoping sight distance cannot be obtained in rural areas a [[Media:234.2 Figure 1 Diamond type Interchange Ramps.pdf\|deceleration lane]] length of 350 ft. is used.

	Where interchanges are closely spaced (e.g. less than 2500 ft.) the auxiliary lane for acceleration will be extended to the exit of the next interchange. An entrance lane followed by a lane exiting forms a traffic weaving section that requires added pavement width and length for weaving capacity. The capacity of the auxiliary lane connecting the on-ramp with the off-ramp will be determined using the Highway Capacity Manual or an appropriate traffic-modeling program (i.e. VISSIM). The weaving section will have a length and number of lanes based on the appropriate level of service outlined in the [[:category:232 Facility Selection\|Facility Selection]] article.		Where interchanges are closely spaced (e.g. less than 2500 ft.) the auxiliary lane for acceleration will be extended to the exit of the next interchange. An entrance lane followed by a lane exiting forms a traffic weaving section that requires added pavement width and length for weaving capacity. The capacity of the auxiliary lane connecting the on-ramp with the off-ramp will be determined using the Highway Capacity Manual or an appropriate traffic-modeling program (i.e. VISSIM). The weaving section will have a length and number of lanes based on the appropriate level of service outlined in the [[:category:232 Facility Selection\|Facility Selection]] article.

Smithk at 20:00, 4 January 2013

2013-01-04T20:00:33Z

← Older revision		Revision as of 15:00, 4 January 2013
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	\|-		\|-
	\|[[media:Green Book Table 10-5.pdf\|'''Green Book Table 10-5''', "Minimum Deceleration Lengths for Exit Terminals"]]		\|[[media:Green Book Table 10-5.pdf\|'''Green Book Table 10-5''', "Minimum Deceleration Lengths for Exit Terminals"]]
			\|-
			\|[[media:Green Book Fig 10-73.pdf\|'''Green Book Figure 10-73''', "Typical Two-Lane Entrance Ramps"]]
	\|-		\|-
	\|[[media:Green Book Fig 10-74.pdf\|'''Green Book Figure 10-74''', "Two Lane Exit Terminals"]]		\|[[media:Green Book Fig 10-74.pdf\|'''Green Book Figure 10-74''', "Two Lane Exit Terminals"]]
	\|-
	~~\|[[media:Green Book Fig 10-73.pdf\|'''Green Book Figure 10-73''', "Typical Two-Lane Entrance Ramps"]]~~
	\|}		\|}

Smithk: Per Design, updated AASHTO figures

2013-01-04T19:58:14Z

Per Design, updated AASHTO figures

← Older revision		Revision as of 14:58, 4 January 2013
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	\|[[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|Ramp Nose Treatment and Pav't Width Transition]]		\|[[media:234.2 Figure 1 Diamond Interchange Alignment Controls.pdf\|Ramp Nose Treatment and Pav't Width Transition]]
	\|-		\|-
	\|[[~~Media~~:~~234.2 Minimum Acceleration Lengths for Entrance Terminals~~.pdf\|'''Green Book ~~Exhibit~~ 10-70''', "Minimum Acceleration Lengths for Entrance Terminals"]]		\|[[media:Green Book Table 10-3.pdf\|'''Green Book Table 10-3''', "Minimum Acceleration Lengths for Entrance Terminals"]]
	\|-		\|-
	\|[[Media:~~Speed Change Lane Adjustment Factors~~.pdf\|'''Green Book ~~Exhibit~~ 10-71''', "Speed Change Lane Adjustment Factors"]]		\|[[Media:Green Book Table 10-4.pdf\|'''Green Book Table 10-4''', "Speed Change Lane Adjustment Factors"]]
	\|-		\|-
	\|[[~~Media~~:~~234.2 Minimum Deceleration Lengths for Exit Terminals~~.pdf\|'''Green Book ~~Exhibit~~ 10-73''', "Minimum Deceleration Lengths for Exit Terminals"]]		\|[[media:Green Book Table 10-5.pdf\|'''Green Book Table 10-5''', "Minimum Deceleration Lengths for Exit Terminals"]]
	\|-		\|-
	\|[[~~Media~~:~~234.2 Two Lane Exit Terminals~~.pdf\|'''Green Book ~~Exhibit~~ 10-76''', "Two Lane Exit Terminals"]]		\|[[media:Green Book Fig 10-74.pdf\|'''Green Book Figure 10-74''', "Two Lane Exit Terminals"]]
	\|-		\|-
	\|[[~~Media~~:~~234.2 Typical Two~~-~~Lane Entrance Ramps~~.pdf\|'''Green Book ~~Exhibit~~ 10-77''', "Typical Two-Lane Entrance Ramps"]]		\|[[media:Green Book Fig 10-73.pdf\|'''Green Book Figure 10-73''', "Typical Two-Lane Entrance Ramps"]]
	\|}		\|}

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	===234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type)===		===234.2.1.4 Auxiliary Lanes for Acceleration and Deceleration (Parallel Type)===

	Minimum speed change lengths are given in [[~~Media~~:~~234.2 Minimum Acceleration Lengths for Entrance Terminals~~.pdf\|~~Exhibits~~ 10-70]] and [[~~Media~~:~~234.2 Minimum Deceleration Lengths for Exit Terminals~~.pdf\|10-73]] of the AASHTO Green Book. Lengths shown in these tables are for grades of 2% or less on the speed change lane. [[~~Media~~:~~Speed Change Lane Adjustment Factors~~.pdf\|~~Exhibit~~ 10-71]] of the AASHTO Green Book provides adjustment to these lengths for grades over 2%. Speed change lanes are provided at all ramp entrances and exits where the number of through traffic lanes each side of the ramp terminal are equal. The combined length of full width acceleration lane and taper will not be less than 600 ft. A shoulder, at least 6 ft. wide, is provided for auxiliary lanes along the through traffic lanes (except a 4-foot shoulder will be provided along a median acceleration lane). Auxiliary lane width is the same as the width provided for the through traffic lanes. In rural areas, the ramp nose will be visible to approaching traffic for a distance equal to at least 1.25 times the stopping sight distance on the freeway of expressway. When Stoping sight distance cannot be obtained in rural areas a [[Media:234.2 Figure 1 Diamond type Interchange Ramps.pdf\|deceleration lane]] length of 350 ft. is used.		Minimum speed change lengths are given in [[media:Green Book Table 10-3.pdf\|Tables 10-3]] and [[media:Green Book Table 10-5.pdf\|10-5]] of the AASHTO Green Book. Lengths shown in these tables are for grades of 2% or less on the speed change lane. [[media:Green Book Table 10-4.pdf\|Table 10-4]] of the AASHTO Green Book provides adjustment to these lengths for grades over 2%. Speed change lanes are provided at all ramp entrances and exits where the number of through traffic lanes each side of the ramp terminal are equal. The combined length of full width acceleration lane and taper will not be less than 600 ft. A shoulder, at least 6 ft. wide, is provided for auxiliary lanes along the through traffic lanes (except a 4-foot shoulder will be provided along a median acceleration lane). Auxiliary lane width is the same as the width provided for the through traffic lanes. In rural areas, the ramp nose will be visible to approaching traffic for a distance equal to at least 1.25 times the stopping sight distance on the freeway of expressway. When Stoping sight distance cannot be obtained in rural areas a [[Media:234.2 Figure 1 Diamond type Interchange Ramps.pdf\|deceleration lane]] length of 350 ft. is used.

	Where interchanges are closely spaced (e.g. less than 2500 ft.) the auxiliary lane for acceleration will be extended to the exit of the next interchange. An entrance lane followed by a lane exiting forms a traffic weaving section that requires added pavement width and length for weaving capacity. The capacity of the auxiliary lane connecting the on-ramp with the off-ramp will be determined using the Highway Capacity Manual or an appropriate traffic-modeling program (i.e. VISSIM). The weaving section will have a length and number of lanes based on the appropriate level of service outlined in the [[:category:232 Facility Selection\|Facility Selection]] article.		Where interchanges are closely spaced (e.g. less than 2500 ft.) the auxiliary lane for acceleration will be extended to the exit of the next interchange. An entrance lane followed by a lane exiting forms a traffic weaving section that requires added pavement width and length for weaving capacity. The capacity of the auxiliary lane connecting the on-ramp with the off-ramp will be determined using the Highway Capacity Manual or an appropriate traffic-modeling program (i.e. VISSIM). The weaving section will have a length and number of lanes based on the appropriate level of service outlined in the [[:category:232 Facility Selection\|Facility Selection]] article.

	Where a two-lane entrance ramp or a two-lane exit ramp is needed for capacity or lane balance, the effective length of auxiliary lane will be determined as illustrated in [[~~Media~~:~~234.2 Two Lane Exit Terminals~~.pdf\|~~Exhibits~~ 10-76]] and [[~~Media~~:~~234.2 Typical Two~~-~~Lane Entrance Ramps~~.pdf\|10-77]] of the AASHTO Green Book.		Where a two-lane entrance ramp or a two-lane exit ramp is needed for capacity or lane balance, the effective length of auxiliary lane will be determined as illustrated in [[media:Green Book Fig 10-74.pdf\|Figures 10-74]] and [[media:Green Book Fig 10-73.pdf\|10-73]] of the AASHTO Green Book.

	===234.2.1.5 Clear Zones===		===234.2.1.5 Clear Zones===