940 traffic interchanges - us department of transportation · september 2002 page 940-1 940 traffic...

Design Manual Traffic InterchangesSeptember 2002 Page 940-1

940 Traffic Interchanges

A Policy on Geometric Design of Highways andStreets (Green Book), 2001, AASHTO

A Policy on Design Standards - Interstate System,1991, AASHTO

Highway Capacity Manual (Special Report 209),Transportation Research Board

Procedure for Analysis and Design of WeavingSections, A User’s Guide, October 1985,Jack E. Leisch.

940.03 Definitionsauxiliary lane The portion of the roadwayadjoining the traveled way for parking, speedchange, turning, storage for turning, weaving,truck climbing, passing, and other purposessupplementary to through traffic movement

basic number of lanes The minimum numberof general purpose lanes designated andmaintained over a significant length of highway.

collector distributor road (C-D road) A parallelroadway designed to remove weaving from themain line and to reduce the number of main lineentrances and exits.

decision sight distance The sight distancerequired for a driver to detect an unexpectedor difficult-to-perceive information source orhazard, interpret the information, recognize thehazard, select an appropriate maneuver, andcomplete it safely and efficiently.

frontage road An auxiliary road that is a localroad or street located on the side of a highway forservice to abutting properties and adjacent areas,and for control of access.

gore The area downstream from the intersectionof the shoulders of the main line and exit ramp.Although generally the area between a main lineand an exit ramp, the term may also be used torefer to the area between a main line and anentrance ramp.

intersection at grade The general area where astate highway or ramp terminal is met or crossedat a common grade or elevation by another statehighway, a county road, or a city street.

940.01 General940.02 References940.03 Definitions940.04 Interchange Design940.05 Ramps940.06 Interchange Connections940.07 Ramp Terminal Intersections at

Crossroads940.08 Interchanges on Two-Lane Highways940.09 Interchange Plans940.10 Documentation

940.01 GeneralThe primary purpose of an interchange is toeliminate conflicts caused by vehicle crossingsand to minimize conflicting left-turn movements.Interchanges are provided on all Interstatehighways, freeways, other routes on which fullaccess control is required, and at other locationswhere traffic cannot be controlled safely andefficiently by intersections at grade.

See the following chapters for additionalinformation:

Chapter Subject

640 Superelevation640 Turning Widths640 Ramp Sections910 Intersections1050 HOV Lanes1420 Access Control1425 Access Point Decision Report

940.02 ReferencesStandard Plans for Road, Bridge, and MunicipalConstruction (Standard Plans), M 21-01,WSDOT

Plans Preparation Manual, M 22-31, WSDOT

HOV Direct Access Design Guide, DraftM 22-98, WSDOT

Standard Specifications for Road, Bridge,and Municipal Construction (StandardSpecifications), M 41-10, WSDOT.

Traffic Interchanges Design ManualPage 940-2 September 2002

Interstate System A network of routes selectedby the state and the FHWA under terms of thefederal aid acts as being the most important to thedevelopment of a national transportation system.The Interstate System is part of the principalarterial system.

lane A strip of roadway used for a single lineof vehicles.

median The portion of a divided highwayseparating the traveled ways for traffic inopposite directions.

outer separation The area between the outsideedge of traveled way for through traffic and thenearest edge of traveled way of a frontage road.

painted nose The point where the main line andramp lanes separate.

physical nose The point, upstream of the gore,with a separation between the roadways of 16 to22 ft. See Figures 940-11a and 11b.

ramp A short roadway connecting a main laneof a freeway with another facility for vehicularuse such as a local road or another freeway.

ramp connection The pavement at the end ofa ramp, connecting it to a main lane of a freeway.

ramp meter A traffic signal at a freeway entranceramp that allows a measured or regulated amountof traffic to enter the freeway.

ramp terminal The end of a ramp at a localroad.

roadway The portion of a highway, includingshoulders, for vehicular use. A divided highwayhas two or more roadways.

sight distance The length of highway visibleto the driver.

shoulder The portion of the roadwaycontiguous with the traveled way, primarily foraccommodation of stopped vehicles, emergencyuse, lateral support of the traveled way, and(where permitted) use by bicyclists andpedestrians.

stopping sight distance The sight distancerequired to detect a hazard and safely stop avehicle traveling at design speed.

traffic interchange A system ofinterconnecting roadways, in conjunction withone or more grade separations, providing forthe exchange of traffic between two or moreintersecting highways or roadways.

traveled way The portion of the roadwayintended for the movement of vehicles, exclusiveof shoulders and lanes for parking, turning, andstorage for turning.

940.04 Interchange Design(1) GeneralAll freeway exits and entrances, except HOVdirect access connections, are to connect on theright of through traffic. Deviations from thisrequirement will be considered only for specialconditions.

HOV direct access connections may beconstructed on the left of through traffic whenthey are designed in accordance with the HOVDirect Access Design Guide.

Provide complete ramp facilities for all directionsof travel wherever possible. However, giveprimary consideration to the basic trafficmovement function that the interchange isto fulfill.

Few complications will be encountered in thedesign and location of rural interchanges thatsimply provide a means of exchanging trafficbetween a limited access freeway and a localcrossroad. The economic and operational effectsof locating traffic interchanges along a freewaythrough a community requires more carefulconsideration, particularly with respect to localaccess, to provide the best local service possiblewithout reducing the capacity of the major routeor routes.

Where freeway to freeway interchanges areinvolved, do not provide ramps for local accessunless they can be added conveniently andwithout detriment to safety or reduction of rampand through-roadway capacity. When exchangeof traffic between freeways is the basic functionand local access is prohibited by access controlrestrictions or traffic volume, it may be necessaryto provide separate interchanges for local service.


(2) Interchange PatternsBasic interchange patterns have been establishedthat can be used under certain general conditionsand modified or combined to apply to manymore. Alternatives must be considered in thedesign of a specific facility, but the conditionsin the area and on the highway involved mustgovern and rigid patterns must not beindiscriminately imposed.

Selection of the final design must be basedon a study of projected traffic volumes, siteconditions, geometric controls, criteria forintersecting legs and turning roadways, driverexpectancy, consistent ramp patterns, continuity,and cost.

The patterns most frequently used for interchangedesign are those commonly described asdirectional, semidirectional, cloverleaf, partialcloverleaf, diamond, and single point (urban)interchange. (See Figure 940-4.)

(a) Directional A directional interchangeis the most effective design for connection ofintersecting freeways. The directional patternhas the advantage of reduced travel distance,increased speed of operation, and higher capacity.These designs eliminate weaving and have afurther advantage over cloverleaf designs inavoiding the loss of sense of direction driversexperience in traveling a loop. This type ofinterchange is costly to construct, commonlyusing a four-level structure.

(b) Semidirectional A semidirectionalinterchange has ramps that loop around theintersection of the highways. This requiresmultiple single-level structures and more areathan the directional interchange.

(c) Cloverleaf The full cloverleaf interchangehas four loop ramps that eliminate all the left-turnconflicts. Outer ramps provide for the right turns.A full cloverleaf is the minimum type interchangethat will suffice for a freeway-to-freewayinterchange. Cloverleaf designs often incorporatea C-D road to minimize signing difficulties andto remove weaving conflicts from the mainroadway.

The principal advantage of this design is theelimination of all left-turn conflicts with onesingle-level structure. Because all movementsare merging movements, it is adaptable to anygrade line arrangement.

The cloverleaf has some major disadvantages.The left-turn movement has a circuitous routeon the loop ramp, the speeds are low on the loopramp, and there are weaving conflicts betweenthe loop ramps. The cloverleaf also requires alarge area. The weaving and the radius of theloop ramps are a capacity constraint on theleft-turn movements.

(d) Partial Cloverleaf (PARCLO) A partialcloverleaf has loop ramps in one, two, or threequadrants that are used to eliminate the majorleft-turn conflicts. These loops may also serveright turns for interchanges that have one or twoquadrants that must remain undeveloped. Outerramps are provided for the remaining turns.Design the grades to provide sight distancebetween vehicles approaching these ramps.

(e) Diamond A diamond interchange hasfour ramps that are essentially parallel to themajor arterial. Each ramp provides for one rightand one left-turn movement. Because left-turnsare made at grade across conflicting traffic on thecrossroad, intersection sight distance is a primaryconsideration.

The diamond design is the most generallyapplicable and serviceable interchangeconfiguration and usually requires less spacethan any other type. Consider this design firstwhen a semidirectional interchange is requiredunless another design is clearly dictated bytraffic, topography, or special conditions.

(f) Single Point (Urban) A single point urbaninterchange is a modified diamond with all of itsramp terminals on the crossroad combined intoone signalized at-grade intersection. This singleintersection accommodates all interchange andthrough movements.

A single point urban interchange can improve thetraffic operation on the crossroad with less rightof way than a typical diamond interchange;however, a larger structure is required.


(3) SpacingTo avoid excessive interruption of main linetraffic, consider each proposed facility inconjunction with adjacent interchanges,intersections, and other points of access alongthe route as a whole.

The minimum spacing between adjacentinterchanges is 1 mi in urban areas and 2 miin rural areas. In urban areas, spacing less than1 mi may be used with C-D roads or gradeseparated (braided) ramps. Generally, the averageinterchange spacing is not less than 2 mi inurban areas and not less than 4 mi in suburbanareas. Interchange spacing is measured alongthe freeway center line between the center linesof the crossroads.

The spacing between interchanges may alsobe dependent on the spacing between ramps.The minimum spacing between the noses ofadjacent ramps is given on Figure 940-5.

Consider either frontage roads or C-D roadswhen it is necessary to facilitate the operationof near-capacity volumes between closely spacedinterchanges or ramp terminals. C-D roads maybe required where cloverleaf loop ramps areinvolved or where a series of interchange rampsrequires overlapping of the speed change lanes.Base the distance between successive rampterminals on capacity requirements and checkthe intervening sections by weaving analysisto determine whether adequate capacity and sightdistance and effective signing can be ensuredwithout the use of auxiliary lanes or C-D roads.

(4) Route ContinuityRoute continuity refers to the providing ofa directional path along the length of a routedesignated by state route number. Provide thedriver of a through route a path on which lanechanges are minimized and other trafficoperations occur to the right.

In maintaining route continuity, interchangeconfiguration may not always favor the heavytraffic movement, but rather the through route.In this case, design the heavy traffic movementswith multilane ramps, flat curves, and reasonablydirect alignment.

(5) DrainageAvoid interchanges located in proximity tonatural drainage courses. These locations oftenresult in complex and unnecessarily costlyhydraulic structures.

The open areas within an interchange can be usedfor storm water detention facilities when thesefacilities are required.

(6) Uniformity of Exit PatternWhile interchanges are of necessity customdesigned to fit specific conditions, it is desirablethat the pattern of exits along a freeway havesome degree of uniformity. From the standpointof driver expectancy, it is desirable that eachinterchange have only one point of exit, locatedin advance of the crossroad.

940.05 Ramps(1) Ramp Design SpeedThe design speed for a ramp is based on thedesign speed for the freeway main line.

It is desirable for the ramp design speed at theconnection to the freeway be equal to the free-flow speed of the freeway. Meet or exceed theupper range values from Figure 940-1 for thedesign speed at the ramp connection to thefreeway. Transition the ramp design speed toprovide a smooth acceleration or decelerationbetween the speeds at the ends of the ramp.However, do not reduce the ramp design speedbelow the lower range speed of 25 mph. For loopramps, use a design speed as high as practical, butnot less than 25 mph.

These design speed guidelines do not apply to theramp in the area of the ramp terminal at-gradeintersection. In the area of the intersection, adesign speed of 15 mph for turning traffic or0 mph for a stop condition is adequate. Use theallowed skew at the ramp terminal at-gradeintersection to minimize ramp curvature.

For freeway-to-freeway ramps and C-D roads, thedesign speed at the connections to both freewaysis the upper range values from Figure 940-1;however, with justification, the midrange valuesfrom Figure 940-1 may be used for the remainderof the ramp. When the design speed for the twofreeways is different, use the higher design speed.


Existing ramps meet design speed requirementsif acceleration or deceleration requirements aremet (figure 940-8 or 940-10) and superelevationmeets or will be corrected to meet therequirements in Chapter 640.

Main Line Design 50 55 60 65 70 80Speed mph

Upper Range 45 50 50 55 60 70

Midrange 35 40 45 45 50 60

Lower 25 25 25 25 25 25 Range

Ramp Design SpeedFigure 940-1

(2) Sight DistanceDesign ramps in accordance with provisions inChapter 650 for stopping sight distances.

(3) GradeThe maximum grade for ramps for various designspeeds is given in Figure 940-2.

Ramp Design 45 andSpeed (mph) 25-30 35-40 above

Desirable Grade (%) 5 4 3

Maximum Grade (%) 7 6 5

On one-way ramps down grades may be 2%greater.

Maximum Ramp GradeFigure 940-2

(4) Cross SectionProvide the minimum ramp widths given inFigure 940-3. Ramp traveled ways may requireadditional width to these minimums as one-wayturning roadways. See Chapter 640 for additionalinformation and roadway sections.

Number of Lanes 1 2

Traveled Way(1) 15(2) 25(3)

Shoulders Right 8 8Left 2 4

Medians(4) 6 8

(1) See Chapter 640 for turning roadwaywidths. See Chapter 1050 for additionalwidth when an HOV lane is present.

(2) May be reduced to 12 ft on tangents.(3) Add 12 ft for each additional lane.(4) The minimum median width is not less

than that required for traffic controldevices and their respective clearances.

Ramp Widths (ft)Figure 940-3

Cross slope and superelevation requirements forramp traveled way and shoulders are as given inChapter 640 for roadways.

Whenever feasible, make the ramp cross slope atthe ramp beginning or ending station equal to thecross slope of the through lane pavement. Wherespace is limited and superelevation runoff is longor when parallel connections are used, thesuperelevation transition may be ended beyond(for on-ramps) or begun in advance of (foroff-ramps) the ramp beginning or ending station,provided that the algebraic difference in crossslope at the edge of the through lane and the crossslope of the ramp does not exceed 4%. In suchcases, ensure smooth transitions for the edge oftraveled way.

(5) Ramp Lane IncreasesWhen off-ramp traffic and left-turn movementvolumes at the ramp terminal at-gradeintersection cause congestion, it may bedesirable to add lanes to the ramp to reduce thequeue length caused by turning conflicts. Makeprovision for the addition of ramp lanes wheneverramp exit or entrance volumes, after the designyear, are expected to result in poor service. SeeChapter 620 for width transition design.

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(6) Ramp MetersRamp meters are used to allow a measured orregulated amount of traffic to enter the freeway.When operating in the “measured” mode, theyrelease traffic at a measured rate to keepdownstream demand below capacity and improvesystem travel times. In the “regulated” mode,they break up platoons of vehicles that occurnaturally or result from nearby traffic signals.Even when operating at near capacity, a freewaymain line can accommodate merging vehiclesone or two at a time, while groups of vehicleswill cause main line flow to break down.

The location of the ramp meter is a balancebetween the storage and accelerationrequirements. Locate the ramp meter to maximizethe available storage and so that the accelerationlane length, from a stop to the freeway main linedesign speed, is available from the stop bar tothe merging point. With justification, the averagemain line running speed during the hours ofmeter operation may be used for the highwaydesign speed to determine the minimumacceleration lane length from the ramp meter.See 940.06(4) for information on the designof on-connection acceleration lanes. See Chapter860 for additional information on the design oframp meters.

Driver compliance with the signal is requiredfor the ramp meter to have the desired results.Consider enforcement areas with ramp meters.

Consider HOV bypass lanes with ramp meters.See Chapter 1050 for design data for ramp meterbypass lanes.

940.06 Interchange ConnectionsProvide uniform geometric design and uniformsigning for exits and entrances, to the extentpossible, in the design of a continuous freeway.Do not design an exit ramp as an extension of amain line tangent at the beginning of a main linehorizontal curve.

Provide spacing between interchange connectionsas given by Figure 940-5.

Avoid on-connections on the inside of a main linecurve, particularly when the ramp approach angleis accentuated by the main line curve, the ramp

approach requires a reverse curve to connect tothe main line, or the elevation difference willcause the cross slope to be steep at the nose.

Keep the use of mountable curb at interchangeconnections to a minimum. Justification isrequired when it is used adjacent to trafficexpected to exceed 40 mph.

(1) Lane BalanceDesign interchanges to the following principlesof lane balance:

(a) At entrances, make the number of lanesbeyond the merging of two traffic streams notless than the sum of all the lanes on the mergingroadways less one. (See Figure 940-6a.)

(b) At exits, make the number of approachlanes equal the number of highway lanes beyondthe exit plus the number of exit lanes less one.(See Figure 940-6a.) Exceptions to this are at acloverleaf or at closely spaced interchanges witha continuous auxiliary lane between the entranceand exit. In these cases the auxiliary lane maybe dropped at a single-lane, one lane reduction,off-connection with the number of approachlanes being equal to the sum of the highwaylanes beyond the exit and the number of exitlanes. Closely spaced interchanges have adistance of less than 2,100 ft between the endof the acceleration lane and the beginning ofthe deceleration lane.

Maintain the basic number of lanes, as describedin Chapter 620, through interchanges. When atwo-lane exit or entrance is used, maintain lanebalance with an auxiliary lane. (See Figure940-6b.) The only exception to this is whenthe basic number of lanes is changed at aninterchange.

(2) Main Line Lane ReductionThe reduction of a basic lane or an auxiliary lanemay be made at a two-lane exit or may be madebetween interchanges. When a two-lane exit isused, provide a recovery area with a normalacceleration taper. When a lane is droppedbetween interchanges, drop it 1,500 to 3,000 ftfrom the end of the acceleration taper of theprevious interchange. This will allow foradequate signing but not be so far that the driver


will become accustomed to the number of lanesand be surprised by the reduction. (See Figure940-7.)

Reduce the traveled way width of the freewayby only one lane at a time.

(3) Sight DistanceLocate off-connections and on-connections onthe main line to provide decision sight distancefor a speed/path/direction change as describedin Chapter 650.

(4) On-ConnectionsOn-connections are the pavement at the end ofon-ramps, connecting them to the main lane ofa freeway. They have two parts, an accelerationlane and a taper. The acceleration lane allowsentering traffic to accelerate to the freeway speedand evaluate gaps in the freeway traffic. Thetaper is for the entering vehicle to maneuver intothe through lane.

On-connections are either taper type or paralleltype. The tapered on-connection provides directentry at a flat angle, reducing the steering controlneeded. The parallel on-connection adds a laneadjacent to the through lane for acceleration witha taper at the end. Vehicles merge with thethrough traffic with a reverse curve maneuversimilar to a lane change. While the taper requiresless steering control, the parallel is narrower atthe end of the ramp and has a shorter taper at theend of the acceleration lane.

(a) Provide the minimum acceleration lanelength, given on Figure 940-8, for each rampdesign speed on all on-ramps. When the averagegrade of the acceleration lane is 3% or greater,multiply the distance from the MinimumAcceleration Lane Length table by the factorfrom the Adjustment Factor for Grades table.

For existing ramps that do not have significantaccidents in the area of the connection with thefreeway, the freeway posted speed may be usedto calculate the acceleration lane length forpreservation projects. If corrective action isindicated, use the freeway design speed todetermine the length of the acceleration lane.

Document existing ramps to remain in placewith an acceleration lane length less than to thedesign speed as a design exception. Also,include the following documentation in theproject file: the ramp location, the accelerationlength available, and the accident analysis thatshows that there are not significant accidents inthe area of the connection.

The acceleration lane is measured from the lastpoint designed at each ramp design speed(usually the PT of the last curve for each designspeed) to the last point with a ramp width of 12ft. Curves designed at higher design speeds maybe included as part of the acceleration lanelength.

(b) For parallel type on-connections, providethe minimum gap acceptance length (Lg) to allowentering traffic to evaluate gaps in the freewaytraffic and position the vehicle to use the gap.The length is measured beginning at the pointthat the left edge of traveled way for the rampintersects the right edge of traveled way of themain line to the ending of the acceleration lane.(See Figures 940-9b and 9c.) The gap acceptancelength and the acceleration length overlap withthe ending point controlled by the longer of thetwo.

(c) Single-lane on-connections may be eithertaper type or parallel type. The taper type ispreferred; however, the parallel may be usedwith justification. Design single-lane taper typeon-connections as shown on Figure 940-9a andsingle lane parallel type on-connections as shownon Figure 940-9b.

(d) For two-lane on-connections, the paralleltype is preferred. Design two-lane parallelon-connections as shown on Figure 940-9c.A capacity analysis will normally be the basisfor determining whether a freeway lane or anauxiliary lane is to be provided.

When justification is documented, a two-lanetapered on-connection may be used. Designtwo-lane tapered on-connections in accordancewith Figure 940-9d.


(5) Off-ConnectionsOff-connections are the pavement at thebeginning of an off-ramp, connecting it to amain lane of a freeway. They have two parts,a taper for maneuvering out of the through trafficand a deceleration lane to slow to the speed ofthe first curve on the ramp. Deceleration is notassumed to take place in the taper.

Off-connections are either taper type or paralleltype. The taper type is preferred because it fitsthe path preferred by most drivers. When aparallel type connection is used, drivers tendto drive directly for the ramp and not use theparallel lane. However, when a ramp is requiredon the outside of a curve, the paralleloff-connection is preferred. An advantage of theparallel connection is that it is narrower at thebeginning of the ramp.

(a) Provide the minimum deceleration lanelength given on Figure 940-10 for each designspeed for all off-ramps. Also, providedeceleration lane length to the end of theanticipated queue at the ramp terminal. When theaverage grade of the deceleration lane is 3% orgreater, multiply the distance from the MinimumDeceleration Lane Length table by the factorfrom the Adjustment Factor for Grades table.

For existing ramps that do not have significantaccidents in the area of the connection with thefreeway, the freeway posted speed may be usedto calculate the deceleration lane length forpreservation projects. If corrective action isindicated, use the freeway design speed todetermine the length of the deceleration lane.

Document existing ramps to remain in placewith a deceleration lane length less than to thedesign speed as a design exception. Also, includethe following documentation in the project file:the ramp location, the deceleration length avail-able, and the accident analysis that shows thatthere are not significant accidents in the area ofthe connection.

The deceleration lane is measured from the pointwhere the taper reaches a width of 12 ft to thefirst point designed at each ramp design speed(usually the PC of the first curve for each design

speed). Curves designed at higher design speedsmay be included as part of the deceleration lanelength.

(b) Gores, Figures 940-11a and 11b, aredecision points that must be clearly seen andunderstood by approaching drivers. In a seriesof interchanges along a freeway, it is desirablethat the gores be uniform in size, shape, andappearance.

The paved area between the physical nose andthe gore nose is the reserve area. It is reservedfor the installation of an impact attenuator. Theminimum length of the reserve area is controlledby the design speed of the main line. (See Figures940-11a and 11b.)

In addition to striping, raised pavement markerrumble strips may be placed for additionalwarning and delineation at gores. See theStandard Plans for striping and rumble stripdetails.

The accident rate in the gore area is greater thanat other locations. Keep the unpaved area beyondthe gore nose as free of obstructions as possibleto provide a clear recovery area. Grade thisunpaved area as nearly level with the roadwaysas possible. Avoid placing obstructions suchas heavy sign supports, luminaire poles, andstructure supports in the gore area.

When an obstruction must be placed in a gorearea, provide an impact attenuator (Chapter 720)and barrier (Chapter 710). Place the beginning ofthe attenuator as far back in the reserve area aspossible, preferably after the gore nose.

(c) For single-lane off-connections, thetaper type is preferred. Use the design shownon Figure 940-12a for tapered single-lane off-connections. When justification is documented,a parallel single-lane off-connection, as shownon Figure 940-12b, may be used.

(d) The single-lane off-connection with onelane reduction, Figure 940-12c, is only usedwhen the conditions from lane balance for asingle lane exit, one lane reduction, are met.

(e) The tapered two-lane off-connection designshown on Figure 940-12d is preferred where thenumber of freeway lanes is to be reduced, or

Design Manual Traffic InterchangesSeptember 2002 40-9

where high volume traffic operations will beimproved by the provision of a parallel auxiliarylane and the number of freeway lanes is to beunchanged.

The parallel two-lane off-connection, Figure940-12e, allows less operational flexibility thanthe taper, requiring more lane changes. Use aparallel two-lane off-connection only withjustification.

(6) Collector Distributor RoadsA C-D road can be within a single interchange,through two closely spaced interchanges, orcontinuous through several interchanges.Design C-D roads that connect three or moreinterchanges to be two lanes wide. All othersmay be one or two lanes in width, dependingon capacity requirements. Consider intermediateconnections to the main line for long C-D roads.See Figure 940-13a for designs of collectordistributor outer separations. Use Design A, withconcrete barrier, when adjacent traffic in eitherroadway is expected to exceed 40 mph. Design B,with mountable curb, may be used only whenadjacent traffic will not exceed 40 mph.

(a) The details shown in Figure 940-13b applyto all single-lane C-D road off-connections.Where conditions require two-lane C-D roadoff-connections, a reduction in the number offreeway lanes, the use of an auxiliary lane, or acombination of these, design it as a normaloff-connection per 940.06(5).

(b) Design C-D road on-connections as requiredby Figure 940-13c.

(7) Loop Ramp ConnectionsLoop ramp connections at cloverleaf interchangesare distinguished from other ramp connections bya low speed ramp on-connection followed closelyby an off-connection for another low speed ramp.The loop ramp connection design is shown onFigure 940-14. The minimum distance betweenthe ramp connections is dependent on a weavinganalysis. When the connections are spaced farenough apart that weaving is not a consideration,design the on-connection per 940.06(4) andoff-connection per 940.06(5).

(8) Weaving SectionsWeaving sections are highway segments whereone-way traffic streams cross by merging anddiverging. Weaving sections may occur withinan interchange, between closely spacedinterchanges, or on segments of overlappingroutes. Figure 940-15 gives the length of theweaving section for preliminary design. Thetotal weaving traffic is the sum of the trafficentering from the ramp to the main line and thetraffic leaving the main line to the exit ramp inequivalent passenger cars. For trucks, a passengercar equivalent of two may be estimated. Use theHighway Capacity Manual for the final designof weaving sections.

Because weaving sections cause considerableturbulence, interchange designs that eliminateweaving or remove it from the main roadway aredesirable. Use C-D roads for weaving betweenclosely spaced ramps when adjacent to highspeed highways. C-D roads are not required forweaving on low speed roads.

940.07 Ramp TerminalIntersections at CrossroadsDesign ramp terminal intersections at grade withcrossroads as intersections at grade. (See Chapter910.) Whenever possible, design ramp terminalsto discourage wrong way movements. Reviewthe location of ramp intersections at grade withcrossroads to ensure signal progression if theintersection becomes signalized in the future.Provide intersection sight distance as describedin Chapter 910.

In urban and suburban areas, match design speedat the ramp terminal to the speed of the crossroad.Provide steeper intersection angles betweenthe ramp terminal and crossroad to slow motorvehicle traffic speeds and reduce crossingdistances for bicyclists and pedestrians.

The intersection configuration requirements forramp terminals is normally the same as for otherintersections. One exception to this is an anglepoint is allowed between an off ramp and an onramp. This is because the through movement oftraffic getting off the freeway, going through theintersection, and back on the freeway is minor.


Another exception is at ramp terminals wherethe through movement is eliminated (for exampleat a Single Point interchange). For ramp terminalsthat have two wye connections, one for rightturns and the other for left turns and no throughmovement, the intersection angle has littlemeaning and does not need to be considered.

940.08 Interchanges on Two-LaneHighwaysOccasionally, the first stage of a conventionalinterchange will be built with only one directionof the main roadway and operated as a two-lanetwo-way roadway until the ultimate roadway isconstructed.

The design of interchanges on two-lane two-wayhighways may vary considerably from traditionalconcepts due to the following conditions:

• The potential for center-line-crossing relatedaccidents due to merge conflicts or motoristconfusion.

• The potential for wrong way or U-turnmovements.

• Future construction considerations.

• Traffic type and volume.

• The proximity to multilane highway sectionsthat might influence the driver’s impressionthat these roads are also multilane.

The deceleration taper is required for all exitconditions. Design the entering connection witheither the normal acceleration taper or a “buttonhook” type configuration with a stop conditionbefore entering the main line. Consider thefollowing items:

• Design the stop condition connection inaccordance with the requirements for a Teeintersection in Chapter 910. Use this type ofconnection only when an acceleration lane isnot possible. Provide decision sight distanceas described in Chapter 650.

• Since each design will probably vary fromproject to project, analyze each project formost efficient signing placement such asone way, two way, no passing, do not enter,directional arrows, guide posts, and trafficbuttons.

• Prohibit passing through the interchangearea on two lane highways by means ofsigning, pavement marking, or a combinationof both. A 4 ft median island highlighted withraised pavement markers and diagonal stripesis the preferred treatment. When using a 4 ftmedian system, extend the island 500 ftbeyond any merging ramp traffic accelerationtaper. The width for the median can beprovided by reducing each shoulder 2 ftthrough the interchange. (See Figure 940-16.)

• Inform both the entering and throughmotorists of the two-lane two-waycharacteristic of the main line. Includesigning and pavement markings.

• Use as much of the ultimate roadway aspossible. Where this is not possible, leave thearea for future lanes and roadway ungraded.

• Design and construct temporary ramps as ifthey were permanent unless second stageconstruction is planned to rapidly follow thefirst. In all cases, design the connection tomeet the safety needs of the traffic. (SeeFigure 940-16.)

940.09 Interchange PlansFigure 940-17 is a sample showing the generalformat and data required for interchange designplans.

Compass directions (W-S Ramp) or crossroadnames (E-C Street) may be used for rampdesignation to realize the most clarity foreach particular interchange configurationand circumstance.

Include the following as applicable:

• Classes of highway and design speeds formain line and crossroads (Chapter 440).

• Curve data on main line, ramps, andcrossroads.

• Numbers of lanes and widths of lanes andshoulders on main line, crossroads, andramps.


• Superelevation diagrams for the main line,the crossroad, and all ramps (may besubmitted on separate sheets).

• Channelization (Chapter 910).

• Stationing of ramp connections andchannelization.

• Proposed right of way and access controltreatment (Chapter 1420).

• Delineation of all crossroads, existing andrealigned (Chapter 910).

• Traffic data necessary to justify the proposeddesign. Include all movements.

• For HOV direct access connections on theleft, include the statement that the connectionwill be used solely by HOVs or will beclosed.

Prepare a preliminary contour grading plan foreach completed interchange. Show the desiredcontours of the completed interchange includingdetails of basic land formation, slopes, gradedareas, or other special features. Coordinate thecontour grading with the drainage design andthe roadside development plan.

Alternative designs considered, studied, andrejected may be shown as reduced scale diagramswith a brief explanation of the advantages anddisadvantages of the alternative designs,including the recommended design.

940.10 DocumentationThe following documents are to be preservedin the project design documentation file. SeeChapter 330.

� Interchange plan

� Access Point Decision Report(Chapter 1425)

� On-connection type justification

� Off-connection type justification

� Justification for ramp metering mainline speed reduction

� Weaving analysis and design

� Alternative discussion and analysis

� Documentation for acceleration/deceleration lane length based on aspeed less than design speed.


Basic Interchange PatternsFigure 940-4


L = Minimum distance in feet from nose to nose. The nose is the beginning of the unpaved area withinthe gore for an exit and the ending of the unpaved area for an entrance.

A Between two interchanges connected to a freeway, a system interchange2 and a serviceinterchange3.

B Between two interchanges connected to a C-D road, a system interchange2 and a serviceinterchange3.

C Between two interchanges connected to a freeway, both service interchanges3.

D Between two interchanges connected to a C-D road, both service interchanges3.

Notes:

These recommendations are based on operational experience, need for flexibility, and adequatesigning. Check them in accordance with Figure 940-15 and the procedures outlined in theHighway Capacity Manual and use the larger value.

(1) With justification, these values may be reduced for cloverleaf ramps.

(2) A system interchange is a freeway to freeway interchange.

(3) A service interchange is a freeway to local road interchange.

Minimum Ramp Connection SpacingFigure 940-5


Lane BalanceFigure 940-6a


Lane BalanceFigure 940-6b


Main Line Lane Reduction AlternativesFigure 940-7


Acceleration Lane LengthFigure 940-8

Ramp Design Speed (mph) Highway Design

Speed (mph) 0 15 20 25 30 35 40 45 50 60 70

30 180 140 35 280 220 160 40 360 300 270 210 120 45 560 490 440 380 280 160 50 720 660 610 550 450 350 130 55 960 900 810 780 670 550 320 150 60 1200 1140 1100 1020 910 800 550 420 180 65 1410 1350 1310 1220 1120 1000 770 600 370 70 1620 1560 1520 1420 1350 1230 1000 820 580 210 80 2000 1950 1890 1830 1730 1610 1380 1200 970 590 210

Minimum Acceleration Lane Length (ft)

Up Grade Down Grade

Ramp Design Speed

Highway Design

Speed (mph) Grade

20 30 40 50

All Ramp Design Speeds

40 1.3 1.3 0.70 45 1.3 1.35 0.675 50 1.3 1.4 1.4 0.65 55 1.35 1.45 1.45 0.625 60 1.4 1.5 1.5 1.6 0.60 70

3% to less than 5%

1.5 1.6 1.7 1.8 0.60

40 1.5 1.5 0.60 45 1.5 1.6 0.575 50 1.5 1.7 1.9 0.55 55 1.6 1.8 2.05 0.525 60 1.7 1.9 2.2 2.5 0.50 70

5% or more

2.0 2.2 2.6 3.0 0.50

Adjustment Factors for Grades Greater than 3%


On

-Co

nn

ecti

on

(S

ing

le-L

ane,

Tap

er T

ype)

Fig

ure

940

-9a

Not

es:

(1)

See

Fig

ure

940-

8 fo

r ac

cele

ratio

nla

ne le

ngth

LA

.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

era

mp

des

ign

spee

d.

(3)

A tr

ansi

tion

curv

e w

ith a

min

imum

rad

ius

of 3

,000

ft is

des

irab

le. T

hed

esira

ble

leng

th is

300

ft. W

hen

the

mai

n lin

e is

on

a cu

rve

to th

e le

ft, th

etr

ansi

tion

may

var

y fr

om a

3,0

00 ft

rad

ius

to ta

ngen

t to

the

mai

n lin

e.

(4)

Rad

ius

may

be

red

uced

whe

nco

ncre

te b

arrie

r is

pla

ced

bet

wee

nth

e ra

mp

and

mai

n lin

e.

(5)

For

ram

p la

ne a

nd s

houl

der

wid

ths,

see

Fig

ure

940-

3.

(6)

Ap

pro

xim

ate

ang

le to

est

ablis

h ra

mp

alig

nmen

t.

(7)

For

Str

ipin

g, s

ee th

e S

tand

ard

Pla

ns.


Not

es:

(1)

See

Fig

ure

940-

8 fo

r ac

cele

ratio

n la

ne le

ngth

LA

.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

e ra

mp

des

ign

spee

d.

(3)

A tr

ansi

tion

curv

e w

ith a

min

imum

rad

ius

of 3

,000

ft is

des

irab

le. T

he d

esira

ble

leng

th is

300

ft. W

hen

the

mai

n lin

e is

on a

cur

ve to

the

left,

the

tran

sitio

n m

ay v

ary

from

a 3

,000

ftra

diu

s to

tang

ent t

o th

e m

ain

line.

The

tran

sitio

n cu

rve

may

be

rep

lace

d b

y a

50:1

tap

er w

ith a

min

imum

leng

th o

f 300

ft.

On

-Co

nn

ecti

on

(S

ing

le-L

ane,

Par

alle

l Typ

e)F

igu

re 9

40-9

b

(4)

Rad

ius

may

be

red

uced

whe

n co

ncre

te b

arrie

r is

pla

ced

bet

wee

n th

e ra

mp

and

mai

n lin

e.

(5)

For

ram

p la

ne a

nd s

houl

der

wid

ths,

see

Fig

ure

940-

3.

(6)

Ram

p s

tatio

ning

may

be

exte

nded

to a

ccom

mod

ate

sup

erel

evat

ion

tran

sitio

n.

(7)

For

strip

ing

, see

the

Sta

ndar

d P

lans

.


Not

es:

(1)

See

Fig

ure

940-

8 fo

r ac

cele

ratio

n la

nele

ngth

LA

.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

era

mp

des

ign

spee

d.

(3)

A tr

ansi

tion

curv

e w

ith a

min

imum

rad

ius

of 3

,000

ft is

des

irab

le. T

hed

esira

ble

leng

th is

300

ft. W

hen

the

mai

n lin

e is

on

a cu

rve

to th

e le

ft, th

etr

ansi

tion

may

var

y fr

om a

3,0

00 ft

rad

ius

to ta

ngen

t to

the

mai

n lin

e. T

hetr

ansi

tion

curv

e m

ay b

e re

pla

ced

by

a50

:1 ta

per

with

a m

inim

um le

ngth

of

300

ft.

On

-Co

nn

ecti

on

(T

wo

-Lan

e, P

aral

lel T

ype)

Fig

ure

940

-9c

(4)

Rad

ius

may

be

red

uced

whe

nco

ncre

te b

arrie

r is

pla

ced

bet

wee

nth

e ra

mp

and

mai

n lin

e.

(5)

For

ram

p la

ne a

nd s

houl

der

wid

ths,

see

figur

e 94

0-3.

(6)

Ram

p s

tatio

ning

may

be

exte

nded

to a

ccom

mod

ate

sup

erel

evat

ion

tran

sitio

n.

(7)

Ad

ded

lane

or

1,50

0 ft

auxi

liary

lane

plu

s 60

0 ft

tap

er.

(8)

For

strip

ing

, see

the

Sta

ndar

d P

lans

.


On

-Co

nn

ecti

on

(T

wo

-Lan

e, T

aper

Typ

e)F

igu

re 9

40-9

d

Not

es:

(1)

See

Fig

ure

940-

8 fo

r ac

cele

ratio

nla

ne le

ngth

LA

.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

era

mp

des

ign

spee

d.

(3)

A tr

ansi

tion

curv

e w

ith a

min

imum

rad

ius

of 3

,000

ft is

des

irab

le. T

hed

esira

ble

leng

th is

300

ft. W

hen

the

mai

n lin

e is

on

a cu

rve

to th

ele

ft, th

e tr

ansi

tion

may

var

y fr

om a

3,00

0 ft

rad

ius

to ta

ngen

t to

the

mai

n lin

e.

(4)

Rad

ius

may

be

red

uced

whe

nco

ncre

te b

arrie

r is

pla

ced

bet

wee

nth

e ra

mp

and

mai

n lin

e.

(5)

For

ram

p la

ne a

nd s

houl

der

wid

ths,

see

figur

e 94

0-3.

(6)

Ap

pro

xim

ate

ang

le to

est

ablis

h ra

mp

alig

nmen

t.

(7)

Ad

ded

lane

or

1,50

0 ft

auxi

liary

lane

plu

s 60

0 ft

tap

er.

(8)

For

strip

ing

, see

the

Sta

ndar

d P

lans

.


Deceleration Lane lengthFigure 940-10

Highway Design

Ramp Design Speed (mph)

Speed (mph) 0 15 20 25 30 35 40 45 50 60 70

30 235 200 170 140 35 280 250 210 185 150 40 320 295 265 235 185 155 45 385 350 325 295 250 220 155 50 435 405 385 355 315 285 225 175 55 480 455 440 410 380 350 285 235 180 60 530 500 480 460 430 405 350 300 240 65 570 540 520 500 470 440 390 340 280 185 70 615 590 570 550 520 490 440 390 340 240

80 735 710 690 670 640 610 555 510 465 360 265

Minimum Deceleration Length (ft)

Grade Up Grade Down Grade

3% to less than 5%

0.9 1.2

5% or more 0.8 1.35

Adjustment Factors for Grades Greater than 3%


Notes:(1) The reserve area length (L) is not less than:

Main Line Design Speed (mph) 40 45 50 55 60 65 70 80

L (ft) 25 30 35 40 45 50 55 70

(2) Z= , Design speed is for the main line.

(3) R may be reduced, when protected by an impact attenuator.

Gore Area CharacteristicsFigure 940-11a

Design Speed2

Edge of shoulder

Ramp

Edge of traveled way

Painted nose

Physical nose

Reserve area(1)

Gore nose


Edge of shoulder

Z(2)

1

Z(2)

1R = 4 ft min(3)

Edge of thru-lane Edge of shoulder

Shoulder plus 2 ft

4 ft min

Shoulder width

12 ftL(1)

Edge of shoulderEdge of traveled way

Single-Lane Off-Connections No Lane Reduction


Notes:(1) The reserve area length (L) is not less than:

Main Line Design Speed (mph) 40 45 50 55 60 65 70 80

L (ft) 25 30 35 40 45 50 55 70

(2) Z= , Design speed is for the main line.

(3) R may be reduced, when protected by an impact attenuator.

Gore Area CharacteristicsFigure 940-11b

Design Speed2

Edge of shoulder

Ramp


Painted nose

Physical nose

Reserve area(1)

Gore nose


Edge of shoulder

Single-Lane, One-Lane Reduction Off-Connections

and All Two-Lane Off-Connections

Shoulder plus 2 ft

4 ftZ(2)

1

Edge of thru-lane

Edge of shoulderEdge of traveled way

12 ft

L(1)

Edge of shoulder

Shoulder width

R = 4 ft min(3)

4 ft min

50

1


Off

-Co

nn

ecti

on

(S

ing

le-L

ane,

Tap

er T

ype)

Fig

ure

940

-12a

Not

es:

(1)

See

Fig

ure

940-

10 fo

r d

ecel

erat

ion

lane

leng

th L

D.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

e ra

mp

des

ign

spee

d.

(3)

See

Fig

ure

940-

11a

for

gor

ed

etai

ls.

(4)

For

ram

p la

ne a

nd s

houl

der

wid

ths,

see

Fig

ure

940-

3.

(5)

Ap

pro

xim

ate

ang

le to

est

ablis

hra

mp

alig

nmen

t.

(6)

For

strip

ing

, see

the

Sta

ndar

d P

lans

.


Not

es:

(1)

See

Fig

ure

940-

10 fo

r d

ecel

erat

ion

lane

leng

th L

D.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

era

mp

des

ign

spee

d.

Off

-Co

nn

ecti

on

(S

ing

le-L

ane,

Par

alle

l Typ

e)F

igu

re 9

40-1

2b

(3)

See

Fig

ure

940-

11a

for

gor

ed

etai

ls.

(4)

For

ram

p la

ne a

nd s

houl

der

wid

ths,

see

Fig

ure

940-

3.

(5)

Ram

p S

tatio

ning

may

be

exte

nded

to a

ccom

mod

ate

sup

erel

evat

ion

tran

sitio

n.

(6)

For

strip

ing

, see

the

Sta

ndar

d P

lans

.


Not

es:

(1)

See

Fig

ure

940-

10 fo

r d

ecel

erat

ion

lane

leng

th L

D.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

e ra

mp

des

ign

spee

d.

(3)

See

Fig

ure

940-

11b

for

gor

e d

etai

ls.

(4)

For

ram

p la

ne a

nd s

houl

der

wid

ths,

see

Fig

ure

940-

3.

Off

-Co

nn

ecti

on

(S

ing

le-L

ane,

On

e-L

ane

Red

uct

ion

)F

igu

re 9

40-1

2c(5)

Ap

pro

xim

ate

ang

le to

est

ablis

hra

mp

alig

nmen

t.

(6)

Aux

iliar

y la

ne b

etw

een

clos

ely

spac

ed in

terc

hang

es to

be

dro

pp

ed.

(7)

For

strip

ing

, see

the

Sta

ndar

d P

lans

.


Not

es:

(1)

See

Fig

ure

940-

10 fo

r d

ecel

erat

ion

lane

leng

th L

D.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

era

mp

des

ign

spee

d.

(3)

See

Fig

ure

940-

11b

for

gor

e d

etai

ls.

Off

-Co

nn

ecti

on

(T

wo

-Lan

e, T

aper

Typ

e)F

igu

re 9

40-1

2d

(4)

For

ram

p la

ne a

nd s

houl

der

wid

ths,

see

Fig

ure

940-

3.

(5)

Ap

pro

xim

ate

ang

le to

est

ablis

h ra

mp

alig

nmen

t.

(6)

Lane

to b

e d

rop

ped

or

auxi

liary

lane

with

a m

inim

um le

ngth

of

1,50

0 ft

with

a 3

00 ft

tap

er.

(7)

For

strip

ing

, see

the

Sta

ndar

dP

lans

.


Not

es:

(1)

See

Fig

ure

940-

10 fo

r d

ecel

erat

ion

lane

leng

th L

D.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

e ra

mp

des

ign

spee

d.

(3)

See

Fig

ure

940-

11b

for

gor

e d

etai

ls.

Off

-Co

nn

ecti

on

(T

wo

-Lan

e, P

aral

lel T

ype)

Fig

ure

940

-12e

(4)

For

ram

p la

ne a

nd s

houl

der

wid

ths,

see

Fig

ure

940-

3.

(5)

Ram

p s

tatio

ning

may

be

exte

nded

to a

ccom

mod

ate

sup

erel

evat

ion

tran

sitio

n.

(6)

Lane

to b

e d

rop

ped

or

auxi

liary

lane

with

a m

inim

um le

ngth

of 1

,500

ft w

itha

300

ft ta

per

.

(7)

For

strip

ing

, see

the

Sta

ndar

d P

lans

.


Co

llect

or

Dis

trib

uto

r (O

ute

r S

epar

atio

ns)

Fig

ure

940

-13a

Not

es:

(1)

With

just

ifica

tion,

the

conc

rete

bar

rier

may

be

pla

ced

with

2 ft

bet

wee

n th

e ed

ge

of e

ither

sho

uld

er a

nd th

e fa

ce o

f bar

rier.

The

min

imum

wid

th b

etw

een

the

edg

e of

thro

ugh-

shou

lder

and

the

edg

e of

C-D

roa

d s

houl

der

will

be

red

uced

to 6

ft,

and

the

rad

ius

at th

e no

se w

ill b

e re

duc

ed to

3ft.

(2)

For

colle

ctor

dis

trib

utor

roa

d la

ne a

nd s

houl

der

wid

ths,

see

ram

p la

ne a

nd s

houl

der

wid

ths,

Fig

ure

940-

3.


Co

llect

or

Dis

trib

uto

r (O

ff-C

on

nec

tio

ns)

Fig

ure

940

-13b

(4)

For

C-D

roa

d a

nd r

amp

lane

and

sho

uld

er w

idth

s, s

eeFi

gur

e 94

0-3.

(5)

Ap

pro

xim

ate

ang

le to

est

ablis

hal

ignm

ent.

Not

es:

(1)

See

Fig

ure

940-

10 fo

r d

ecel

erat

ion

lane

leng

th L

D.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

eC

-D r

oad

or

ram

p d

esig

n sp

eed

.

(3)

See

Fig

ure

940-

11a

for

gor

e d

etai

ls.

(6)

May

be

red

uced

with

just

ifica

tion.

(See

Fig

ure

940-

13a.

)

(7)

For

strip

ing

, see

the

Sta

ndar

d P

lans

.


Co

llect

or

Dis

trib

uto

r (O

n-C

on

nec

tio

ns)

Fig

ure

940

-13c

Not

es:

(1)

See

Fig

ure

940-

8 fo

r ac

cele

ratio

n la

nele

ngth

LA

.

(2)

Poi

nt A

is

the

poi

nt c

ontr

ollin

g th

e ra

mp

des

ign

spee

d.

(3)

A tr

ansi

tion

curv

e w

ith a

min

imum

rad

ius

of 3

,000

ft is

des

irab

le. T

hed

esira

ble

leng

th is

300

ft. W

hen

the

C-D

roa

d is

on

a cu

rve

to th

e le

ft,th

e tr

ansi

tion

may

var

y fr

om a

3,0

00ft

rad

ius

to ta

ngen

t to

the

C-D

roa

d.

(4)

For

C-D

roa

d a

nd r

amp

lane

and

shou

lder

wid

ths,

see

Fig

ure

940-

3.

(5)

Ap

pro

xim

ate

ang

le to

est

ablis

hal

ignm

ent.

(6)

May

be

red

uced

with

just

ifica

tion.

(See

Fig

ure

940-

13a.

)

(7)

For

strip

ing

, see

the

Sta

ndar

d P

lans

.


Lo

op

Ram

ps

Co

nn

ecti

on

sF

igu

re 9

40-1

4

Not

es:

(1)

See

Fig

ure

940-

15 fo

r re

qui

red

min

imum

wea

ving

leng

th.

(2)

For

min

imum

ram

p la

ne a

nd s

houl

der

wid

ths,

see

Fig

ure

940-

3.

(3)

See

Fig

ure

940-

11b

for

gor

e d

etai

ls.


Length of Weaving SectionsFigure 940-15


Tem

po

rary

Ram

ps

Fig

ure

940

-16


Inte

rch

ang

e P

lan

Fig

ure

940

-17

940 traffic interchanges - us department of transportation · september 2002 page 940-1 940 traffic...

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