6.0 DETAILED TRAFFIC OPERATIONS ANALYSIS · CH 42 Corridor Study Detailed Traffic Operations...

CH 42 Corridor Study Detailed Traffic Operations AnalysisFinal Report February 18, 1999#25188 6-1

6.0 DETAILED TRAFFIC OPERATIONS ANALYSIS

6.1 OVERVIEW

This chapter documents the technical analysis of traffic operations for the CH 42 Corridor Study. The analysis consisted of eight different scenarios that included various combinations of signalphasing, roadway geometry, signal removal, and supporting roadway improvements. Each scenariowas modeled using traffic simulation software. Developing the recommended mitigative scenario wasan iterative process, with each scenario building on the scenarios that preceded it. The technicalanalysis process illustrated on Figure 6-1 shows how the analysis was structured and how eachscenario relates to the others. What follows in this section is a description of each scenario and adiscussion of the results. The final portion of this section describes a scenario and the results of themodeling effort of a preliminary set of recommended roadway improvements. These preliminaryrecommendations will be reviewed in the Environmental Overview of Chapter 7.0 before a finalRecommended Corridor Implementation Plan is offered in Chapter 8.0.

6.2 EXISTING CONDITIONS

This section summarizes the existing roadway characteristics and traffic operations along the CH 42Corridor between TH 169 and TH 55. Key characteristics of the roadway include the cross section(number of lanes), traffic control measures, intersection layout, and access spacing. The summary ofexisting traffic operations along the corridor includes annual average daily traffic volume (AADT),peak hour volumes at key intersections, an intersection capacity analysis, an arterial roadway capacityanalysis, and an analysis of existing vehicular crash data.

6.2.1 Roadway Characteristics

Cross Section

Roadway cross section is a primary factor in the operation, capacity and safety of an arterial segment.Cross section design also affects the level of accessibility and right-of-way requirements for an arterialroadway.

Figure 6-2 contains illustrations of typical roadway cross sections along the CH 42 Corridor, and amap showing the existing cross section locations is provided in Figure 6-3. As of 1996, the existingroadway cross sections along the corridor included the following:

Two-Lane – CH 78 between US 169 and CH 17; CH 17 between CH 78 and CH 42; CH 42between CH 17 and a point west of CH 18.

Four-Lane Divided – CH 42 between a point west of CH 18 and CH 5.


Six-Lane Divided – CH 42 between CH 5 and Portland Avenue.

Four-Lane Divided – CH 42 between Portland Avenue and TH 52.

Two-Lane Divided – CH 42 between TH 52 and TH 55.

Traffic Control

Figure 6-4 shows the location and characteristics of the existing traffic control measures along theCH 42 Corridor, including stop signs, traffic signals, and coordinated signal systems. Currently, theCH 42 Corridor has 39 signalized intersections and two coordinated signal systems.

Intersection Layout

Existing configurations for 60 key intersections along the CH 42 Corridor are included inAppendix B. Appendix B also includes the intersection configuration and phasing for each scenariomodeled in the technical analysis process.

Access Spacing

Access spacing is an important factor in arterial roadway operations and safety. Table 6-1 summarizesthe existing access points in each segment of the CH 42 Corridor by classification and type. Accessclassifications include roadway intersections. Access types include full access and partial access (i.e.,three-quarter access and right-in/right-out access). The different access types are described belowand shown schematically in Figures 6-5 to 6-8:

Full - Access – No turning movements to or from the arterial roadway are prohibited.

Three-Quarter Access – A median prohibits left turns and through movements from thecross street, but left turns from the arterial Roadway are allowed. Because there are fewerconflict points, three-quarter access intersections usually have lower crash rates. Based uponan analysis by Dakota County, the average crash rate at three-quarter access intersections is70 percent lower than the average for full-access intersections.

Right-In/Right-Out – A median prohibits left turns and through movements from the crossstreet, and left turns from the arterial roadway. These intersections have the lowest numberof conflict points.

As indicated in Table 6-1, there are 406 access points along the CH 42 Corridor, including 169 public streets and 237 driveways. The average access density ranges from 21.4 per mile in Segment9 (Irving Avenue to I-35W) to 8.8 per mile in Segment 14 [CH 31 (Pilot Knob Road) to TH 3].


6.2.2 Existing Conditions Traffic Operations Analysis

Annual Average Daily Traffic Volume

The 1996 annual average daily traffic volume (AADT) for each segment of the CH 42 Corridor isshown in Table 6-2. Average daily traffic volumes along the corridor range from 48,000 vehicles perday in Segment 10 (I-35W to I-35E) to 5,400 vehicles per day in Segment 1 (TH 169 to CH 17).

Peak Hour Intersection Volume

This study uses PM peak hour traffic volumes as the basis for the intersection traffic operationsanalysis. Table 6-3 documents the 1996 PM peak hour turning movements at the existing signalizedintersections in the CH 42 Corridor. As indicated by the table, existing turning movement countswere not available for 13 of the existing signalized intersections. For these intersections, the turningmovements presented in Table 6-3 were estimated using the following approach:

1. Estimate mainline peak hour approach volumes:a. From adjacent signalized intersections (or)b. From average daily traffic volumes

2. Estimate cross street peak hour approach volumes:a. From average daily traffic volumes (or)b. From volume thresholds for peak-hour traffic signal warrants

3. Approximate peak hour turning volumes using available data from similar CH 42 intersectionsalong CH 42.

The estimation of existing peak hour turning movements for each intersection was necessary in orderto develop a complete set of data required for the traffic operations model.

Existing peak hour turning movements for each of the 60 key intersections along the CH 42 corridorare included in Appendix C. Appendix C also includes peak hour turning movements at each of the60 key intersections for each scenario modeled in the technical analysis process.

Level of Service

The approach to the traffic operations analysis was derived from established methodologiesdocumented in the Highway Capacity Manual, Third Edition (TRB, 1994). The Highway CapacityManual (HCM) contains a series of analysis techniques that are used to evaluate the operation oftransportation facilities under specified conditions.

The results of an HCM analysis are typically presented in the form of a letter grade (A-F) thatprovides a qualitative indication of the operational efficiency or effectiveness. The letter grade


assigned to HCM analysis results is referred to as the level-of-service (LOS). By definition, LOS Aconditions represent high-quality operations (i.e., motorists experience very little delay orinterference) and LOS F conditions represent very poor operations (i.e., extreme delay or severecongestion).

In most large urban areas like the Minneapolis/St. Paul region, state and local agencies define theonset of congestion as the LOS D/E boundary. That threshold has been adopted as the definition ofcongested conditions for the CH 42 Corridor Study.

It is important to note that level-of-service is defined differently for the two HCM analysis techniquesapplied in this study. The intersection analysis focuses on the average delay for all traffic at anintersection, and the arterial roadway analysis focuses on the net travel speed along a roadwaysegment, which may include several intersections. It is, therefore, possible to have an efficientintersection located along a poorly operating roadway segment, or a poorly operating intersectionalong an otherwise free-flowing arterial.

Intersection Capacity Analysis

Level of service at roadway intersections is primarily a function of peak hour turning movementvolumes, intersection lane configuration, and traffic control measures. For intersection analysis,HCM defines LOS in terms of the average stopped delay experienced by a vehicle at the intersectionin seconds per vehicle.

The stopped delay criteria for the LOS thresholds at signalized intersections are as follows:

• LOS A - <5 seconds• LOS B - 5-15 seconds• LOS C - 15-25 seconds• LOS D - 25-40 seconds• LOS E - 40-60 seconds• LOS F - >60 seconds

The HCM sets the LOS D/E boundary at 40 seconds per vehicle for signalized intersections. If theanalysis indicates that the average delay at an intersection exceeds those levels, the intersection isassumed to experience congestion.

Table 6-4 documents the results of the intersection capacity analysis for the existing signalizedintersections. Table 6-4 also shows the results of the intersection capacity analysis for each of thescenarios modeled in the technical analysis process. In this table only intersections that had existingturning movement counts are presented. The results of the capacity analysis show that currently onlyone intersection in the corridor is operating over capacity during the peak hour. However, it doesshow that five other intersections currently operate at level of service D or worse.


Arterial Roadway Capacity Analysis

Arterial roadway segment level-of-service is a function of traffic volume, traffic flow characteristics,roadway cross section, traffic signal spacing and traffic signal timing. For arterial roadway analysis,LOS is defined in terms of the average peak hour travel speed along a segment, including delay andstops:

• LOS A - > 35 mph• LOS B - 28-35 mph• LOS C - 22-28 mph• LOS D - 17-22 mph• LOS E - 13-17 mph• LOS F - < 13 mph

The HCM sets the LOS D/E boundary at 17 mph for arterial classification I, which is an appropriateclassification for most of CH 42. If the analysis indicates that the average peak hour travel speedalong a segment of the roadway is less than 17 mph, the intersection is assumed to have congestion.

Table 6-5 documents the existing speed and level of service according to the traffic operationsanalysis. Table 6-5 also shows the expected speed and level of service for each of the scenariosmodeled in the technical analysis process. The speed documented is an average two-way peak hourtravel speed that includes signal delay and stops. The results of this analysis have been compared withseveral existing travel time runs along the CH 42 corridor, and appear to accurately depict theexisting conditions. The table also lists the Year 2020 speed objective for each segment.

Corridor Crash Rates

Current crash rates along the CH 42 Corridor were identified through the Mn/DOT statewide crashdatabase. Table 6-6 shows the existing crash rates on different segments of the corridor. Theseresults suggest that CH 42 has crash rates that are lower than the statewide average. Intersectioncrash rates at selected locations are summarized in Table 6-7. In addition, recent research forMn/DOT indicates that there is a statistically significant correlation between crash rates and accessdensity. Figure 6-9 illustrates that relationship for urban four-lane arterials with left turn lanes.

6.2.3 Existing Conditions Summary

This section provided an analysis of the existing traffic operations along the CH 42 corridor. Theresults indicate that, although there are areas of significant congestion, most of the corridor operatesacceptably.


6.3 YEAR 2020 NO-BUILD SCENARIO

In order to properly analyze and estimate the traffic operations in Year 2020 and the effect ofpotential mitigation measures a base model detailing the future conditions of the CH 42 Corridorneeded to be determined. The purpose of this section is to document the assumed build-outconditions of the CH 42 corridor for Year 2020 and the analysis of these conditions.

6.3.1 No-Build Assumptions

The Year 2020 No-Build scenario is used to represent changes to the roadway network that areassumed to exist in the forecast year. These changes include only completed improvements, currentwork, and committed improvements. In addition to these improvements it also was necessary toinclude assumptions about future traffic signal locations along CH 42.

Committed Improvements / Assumed Roadway Geometry

The committed roadway improvements (those projects contained in approved Capital ImprovementPrograms) that were assumed to exist in Year 2020 were based upon information provided by DakotaCounty and Scott County. Figure 6-2 contains illustrations of typical roadway cross sections alongCH 42 and Figure 6-10 contains a map showing the typical cross sections on the CH 42 corridor withthe committed improvements, those improvements that are identified in the various agencies 5 YearCapital Improvement Programs, for which funding has been committed.

The following is a summary of the committed improvements assumed for the CH 42 Corridor:

• Extension of the four-lane divided section of CH 42 from west of CH 18 to CH 17. Thisimprovement would also include left and right turn lanes on CH 42 at every signalizedintersection in the segment under consideration.

• Improvement of CH 27 to a four-lane cross section to the north of CH 42.

• Upgrading Dakota CH 31(Pilot Knob Road) to a four-lane cross section. This improvementincludes adding dual left turn lanes on the Dakota CH 31(Pilot Knob Road) approaches to CH42.

Assumed Signal Locations

In order to develop a complete network that would accurately depict the conditions in Year 2020,it was necessary to assume likely locations of future signalized intersections along the CH 42 corridor. These “build-out” traffic signal locations were determined based on existing spacing policies,potential development patterns and the recommendations of City staff. In general, this placedsignalized intersections at approximately half-mile spacing except in areas of low potentialdevelopment at the eastern and western ends of the CH 42 corridor.


Figure 6-11 shows and Table 6-8 gives a complete list of both the existing signalized intersectionsand of the locations assumed in the build-out scenario for signalized intersections. This table showsthat there are 39 existing signalized intersections along the CH 42 corridor and that the build-out ofsignals adds 21 signalized intersections to the corridor. This brings the total number of signalizedintersections on the CH 42 corridor in the build-out condition to 60. Table 6-9 shows the averagesignal spacing in each segment for both existing and the build-out condition. This table shows thatthe build-out of signalized intersections decreases the average signal spacing from over three-quartersof a mile to approximately one-half of a mile.

Lane Geometry at Assumed Signal Locations

Once the build-out of the signalized intersections was determined, lane geometry and signal phasingneeded to be assumed for each new signalized intersection. The following standard was used for eachsignalized intersection added in the build-out scenario:

• Two lanes on each minor street approach (i.e., 1 exclusive left lane and 1 shared through/rightlane).

• Permitted left turn phasing for each minor street approach. • Exclusive left and right turning lanes for each major street approach. • Exclusive left turn phasing for each major street approach.

Peak Hour Turning Movement Volumes

The final step in defining the no-build scenario was determining PM peak hour turning movementvolumes for each intersection. For intersections where existing peak hour approach volumes hadbeen obtained, volumes were estimated by factoring-up the existing turning movement volumes inaccordance with the forecasted increase in AADT. For intersections where existing turningmovements were not available, volumes were estimated using the same approach described in Section6.2.2 for estimating existing turning movement counts.

6.3.2 No-Build Traffic Operations Analysis


Table 6-4 shows the results of the intersection capacity analysis for the signalized intersections underthe No-Build Scenario. As stated earlier, this table only presents results for intersections with existingturning movement counts. The results show that 12 signalized intersections are expected to provideLOS E operations or worse in the Year 2020 No-Build Scenario, and that congestion getssignificantly worse at several other locations.



Table 6-5 documents the expected speed and arterial level-of-service according to the computermodeling. The results show that 7 segments are expected to operate with an average speed of 15mph or less. Furthermore, these results show that only 1 of the 16 segments meets the identifiedspeed objective for the Year 2020.

6.3.3 No-Build Summary

It is apparent from the results of the No-Build Scenario that if the CH 42 corridor develops asexpected and no additional roadway improvements are made that traffic operations will continuallyget worse and significant portions of the roadway will be forced to operate at very heavy levels ofcongestion during peak traffic periods. For this reason it is necessary to explore a variety of optionsthat will effectively mitigate the expected traffic congestion in order to provide reasonable level ofoperations, consistent with the adopted objectives for intersection LOS and travel speed.

6.4 SUPPORTING ROADWAY SCENARIO

As the results of the Year 2020 No-Build analysis indicate, traffic congestion along the CH 42Corridor is expected to become more severe and more extensive. The first phase of the mitigationanalysis focused on potential improvements to the supporting roadway network consistent with therecommendations of the Technical and Advisory Committees. The primary objective of theSupporting Roadway Scenario was to evaluate the potential of adjacent roadway improvements toprovide relief to CH 42 and in order to not focus all mitigative efforts solely in the CH 42 Corridor.

6.4.1 Supporting Roadway Elements

Eleven different supporting roadway projects were identified by the Technical and AdvisoryCommittees and evaluated based upon their ability to divert traffic from CH 42 along with theirprobability of implementation during the typical 20-year planning horizon. Using these criteria it wasdetermined whether or not each alternative should be part of the recommended plan for the corridor.Once each alternative was evaluated, a final scenario was modeled that included all recommendedsupporting roadway improvements. The Year 2020 estimated average daily traffic volumes on CH42 for the supporting roadway scenario are documented in Table 6-2.

Figure 6-12 shows the eleven supporting roadways and the following describes each proposedimprovement:

CR 46 Extension - This improvement includes the extension of CR 46 west from CH 5 to CH 27. This segment was not included in the Supporting Roadway System. Even though this extensionwould divert almost 7,000 vehicles per day, the probability of implementation by Year 2020 wasdetermined to be low because of potential environmental impacts in Murphy-Hanrehan RegionalParkand because of opposition by several government agencies and adjacent landowners. (Not Included)


150th Street/Crystal Lake Road Extension - This improvement includes the extension of 150th

Street / Crystal Lake Road, along a new alignment, west to CR 74. (Included)

CH 38 (McAndrews Road)/I-35W Interchange - This improvement includes a CH 38 (McAndrewsRoad) / I-35W half-diamond interchange to the north. (Included) Mn/DOT may want to considereliminating present southbound lane drop between Burnsville Parkway and CH 42 by extending theoutside through lane to CH 42. This could provide better freeway operations by eliminating the lanechange and the merge lane and the weave to CH 42 exit.

CH 38 (McAndrews Road) Extension - This improvement includes the extension of CH 38(McAndrews Road) west from CH 5 to Burnsville Parkway combined with an upgrade of SouthcrossDrive between CH 5 and CH 42. (Included)

Connelly Parkway Extension - This improvement includes the extension of Connelly Parkway fromCH 27 to CH 17. (Included)

147th Street and 153rd Street Extensions - This improvement includes the extension of 147th Streetfrom Galaxie Avenue to Dakota CH 31 (Pilot Knob Road) and the extension of 153rd Street fromGalaxie Avenue to Dodd Boulevard. (Included)

CH 42 Connection to CR 78 - This improvement includes the connection of CH 42 directly toCR 78 at CH 17. This segment was not included because the analysis suggested that this connectionwould not divert traffic from CH 42 and because of the lack of support by local government agenciesand area residents. (Not Included)

140th Street Extension - This improvement includes the extension of 140th Street east from ShannonParkway to CH 71 (Rich Valley Blvd). (Included)

Reroute TH 55 - This improvement involves rerouting TH 55 along CH 42 to TH 52. It includesadding two interchanges to TH 52. The interchanges would be added at 117th Street and possiblyCH 32 (Cliff Road) with an upgrade to the CH 42 interchange. This improvement eliminates theunconventional interchange between TH 55 and TH 52. It also includes turning back CourthouseBoulevard to the City or County, and extending Courthouse Boulevard north to future CH 32 (CliffRoad). This improvement eliminates the need for a traffic signal at the intersection of CH 42 and TH55. (Included)

TH 13 Design Upgrade - This improvement includes upgrading TH 13 to a freeway between I-35Wand TH 169 (Shakopee Bypass). This segment was not included because the analysis suggested thatthe upgrading would not divert much traffic from CH 42 and because the probability ofimplementation is low (this segment is not identified as an expansion corridor in the Mn/DOT MetroDivision Transportation System Plan).(Not Included)


CH 21 Extension - This improvement includes extending CH 21 south from the Shakopee Bypass(TH 169) to CH 42. This improvement would require the reconstruction of the intersection of CH21 and CH 42. The expected geometry at this intersection that will be modeled in this scenario is afour-lane cross section with left and right turn lanes for each approach. (Included)

6.4.2 Supporting Roadway Traffic Operations Analysis


Table 6-4 shows the results of the intersection capacity analysis for signalized intersections under theSupporting Roadway Scenario. The results show that 11 intersections would operate at LOS E orworse in the forecast year. However, it also shows a reduction in delay at almost every signalizedintersection due to the expected reduction in AADT on CH 42 associated with the SupportingRoadway Scenario.


Table 6-5 documents the speed and level of service according to the computer modeling. The resultsof this analysis show that the Supporting Roadway Scenario increases the expected speed on allsegments of the CH 42 Corridor as well as increasing the weighted average speed on the corridor byalmost 20 percent (22 mph to 26 mph).

6.4.3 Supporting Roadway Summary

The results of this scenario show that the supporting roadway elements provided a significantdecrease in the projected traffic volumes along the CH 42 Corridor. This resulted in a significantbenefit to the traffic operations along the corridor. It is also clear from the results of this scenariothat the supporting roadways alone do not sufficiently mitigate the expected congestion on the CH42 Corridor in order to meet the adopted LOS and travel speed objectives.

6.5 SCENARIO 1: LOW COST MITIGATIONS

The purpose of this analysis is to evaluate mitigations to the roadway and signal system that can bedone at a low cost, are relatively easy to implement, and that have little to no impact on adjacentproperties. Typically, these mitigations focus on increasing the efficiency of the existing roadway. What follows is a discussion of the types of improvements that this scenario considered, the criteriaof their implementation, examples of their benefit, and results of the analysis.

6.5.1 Low Cost Mitigations

Figure 6-13 gives an overview of the low cost mitigations and Table 6-10 lists the different types oflow cost mitigations and the intersections at which they were implemented. This section contains adescription of each type of low cost mitigation and an example of its benefit.


Cross-Street Auxiliary Lane - This mitigation involves adding either a left turn lane or a right turnlane to the minor street approaches. The premise of this mitigation is to add to the capacity of theminor street in order to reduce the length of the signal phase needed to accommodate minor streettraffic. This allows more time to be given to the CH 42 through phases which in turn increasesaverage operating speeds for CH 42 through traffic. This mitigation is most effective when anapproach has a high percentage of either left or right turns.

Cross-Street Through Lane - This mitigation involves adding an extra through lane to the minorstreet approach. This mitigation is also based on adding capacity to the minor street approach whichincreases operating speeds on CH 42. This mitigation is most beneficial when there is a high volumeof cross street traffic.

Mainline Right Turn Lane - This mitigation involves adding a right turn lane on a CH 42 approachto the minor street. The benefit of this mitigation is the separation of the turning vehicles from thethrough traffic flow. As a result, through vehicles do not have to slow down or stop when rightturning vehicles precede them into the intersection. Furthermore, this mitigation is likely to reducecrash rates by minimizing conflicts.

Elimination of Split Phasing - This mitigation involves removing split phasing (each approach ofa street has a separate phase) from a traffic signal. In general this mitigation would result in greatergreen time for the CH 42 through movements. This mitigation is likely to be combined with addinga left turn phase to the traffic signal as well as a modification to the lane geometry.

Addition of Cross Street Left Turn Phase - This mitigation involves changing the signal phasingof the minor street approach from permitted left turns to a signal phasing that includes an exclusiveleft turn phase. The exclusive left turn phase can either be exclusive/permitted phasing or exclusiveonly phasing, depending on intersection volumes and geometry. This mitigation is most beneficialwhen there are high volumes of left turn vehicles at one approach conflicted by high volumes ofthrough traffic at the opposing approach.

Addition of Right Turn Overlaps - This mitigation provides an additional exclusive signal phasefor the selected right turn movement. This is done by “overlapping” the right turn movement withthe left turn movement on the cross street. For example when an exclusive left turn green arrowcomes up for the westbound to southbound left turn, the northbound to eastbound right turn wouldalso be provided with an exclusive phase (green right arrow). This mitigation is most beneficial withhigh volume right turn movements that are protected by high volume left turn movements.

Addition of Signal Coordination - This mitigation involves coordinating the timing of a group ofadjacent signals in order to provide a progressive movement and minimum delay as vehicles proceedalong the arterial. In general, signal coordination is most beneficial when signals are spaced at one-half mile or less. This is due strictly to the fact that platoons of vehicles tend to disperse as signalspacing increases, which tends to minimize the benefits of progressive movement. The operationalbenefits of signal interconnection are best illustrated by Segment 5 (CH 21 to TH 13) in which the


only significant low cost mitigation was the interconnection of signals. Implementation of signalinterconnection is expected to increase the speed in this segment by over twenty percent (29 mph to35 mph). Furthermore, signal interconnection is an efficient way to increase roadway capacity as itcan generally be implemented with little to no impact to adjacent properties and to the existingroadway infrastructure.

6.5.2 Traffic Operations Analysis


Table 6-4 lists the intersection level of service (LOS) and delay results at the key intersections for theLow Cost Scenario. These results show that low cost mitigations are capable of alleviating some ofthe intersection capacity deficiencies. These mitigations were able to change four intersections thatwere expected to fail in the Year 2020 by improving operations to LOS D or better. Furthermore,several other intersections received LOS increases with the low cost mitigations. However, low costmitigations were unable to improve the operations of seven intersections that still fail. In several ofthese cases it was determined that, given the magnitude of the operational deficiency, no low costmitigations were feasible.


Table 6-5 lists the arterial roadway speed and LOS for each segment of the corridor. These resultsshow that low cost mitigations are capable of increasing the expected operating speed of almost everysegment in the corridor. In several segments these mitigations are expected to raise expect operatingspeeds by over 5 mph. In some segments the expected increase in operating speed comes almostentirely from the benefit from coordinated signals (i.e., Segments 5, 6, and 7). Although these lowcost mitigations show improvements throughout the corridor, they fail to improve any of segmentsenough to meet their target speed. Also, only one segment that was previously failing (Speed lessthen 17 mph) is expected to operate at LOS D (17 mph or greater) with these mitigations.

6.5.3 Low Cost Mitigations Summary

It is apparent from the results of this analysis that the low cost mitigations would improve trafficoperations within the corridor. This combined with the defining characteristics of these mitigationsbeing of low cost and easy to suggest that they should be part of the final plan. However, the resultsalso show that doing only low cost mitigations does not come close to meeting the adopted LOS andtravel speed objectives and further mitigations should be pursued.

6.6 SCENARIO 2A: MODERATE COST GEOMETRY MITIGATIONS

The purpose of this analysis is to determine the extent to which CH 42 would need to be widened inorder to meet the speed and LOS objectives. In general, these improvements consist of adding newcapacity to the existing roadway. As part of this scenario it is assumed that the supporting roadway


and low cost improvements are included as part of this analysis. This scenario also includes capacityimprovements to the minor street approaches that were assumed to have moderate costs or impacts.

6.6.1 Low Cost Geometry Mitigations

Figure 6-14 compares the existing cross section locations for the corridor with the cross sectionlocations analyzed in this Scenario. Table 6-11 lists the different types of moderate cost geometrymitigations used in this scenario and the intersections in which they were implemented. What followsis a description of each type of moderate cost mitigation and an example of their benefit.

Addition of Dual Left Turn Lanes - This mitigation involves dedicating two lanes to a particularleft turn movement as opposed to the one lane that is generally used. This mitigation is consideredto be of moderate cost because it generally involves widening the entire roadway in order to makeroom for the second left turn lane.

Widening of CH 42 - This mitigation involves adding a through lane in each direction for a lengthof roadway. As indicated in Figure 6-14, the following widening was considered for this scenario:

• Extend the 6-lane divided section of CH 42 from Irving Avenue to west of 143rd Street. • Widen CH 42 to an 8-lane section from west of I-35W to east of I-35E. • Extend the 6-lane divided section of CH 42 from Plymouth Avenue to east of CH 31 (Pilot

Knob Road). • Extend the 4-lane divided section of CH 42 from TH 52 to existing TH 55.

Widening of Cross-Street - This mitigation involves either adding an extra through lane for thelength of roadway or to carry the widening far enough from the intersection in order to receive theoperational benefits (generally more than one-quarter mile). The cross streets chosen in this scenariofor widening were not considered to be low cost improvements because widening of these roadwayswould entail a much greater degree of work.

Elimination of Split Phasing - This mitigation involves removing split phasing (each approach ofa street has a separate phase) from a traffic signal. The intersections chosen in this scenario forelimination of split phasing also require significant geometry improvements and therefore were notconsidered to be low cost improvements.

6.6.2 Moderate Cost Geometry Traffic Operations Analysis


Table 6-4 lists the capacity analysis results for the key intersections under Scenario 2A. These resultsshow significant improvements in the intersection LOS for almost every intersection that includedgeometry improvements. In fact six intersections that were previously expected to fail are expectedto operate at LOS D or better in this scenario. The only exception to this is the intersection of CH


42 and CH 23 (Cedar Avenue). In a separate analysis it was determined that 9 total lanes (3 left, 5through, 1 right) on CH 23 (Cedar Avenue) and 7 total lanes (2 left, 4 through, 1 right) on CH 42are required in order to get this intersection to perform at LOS D or better.


Table 6-5 lists the arterial roadway speed and LOS for each segment of the corridor for Scenario 2A. These results show significant increases in expected arterial speed for each segment that includedwidening, in some cases doubling the expected speed. Further review of the results shows that almostevery segment is close to the target speed for that segment. The one exception to this is Segment 13[Pennock Avenue to CH 31 (Pilot Knob Road)] which at an expected speed of 20 mph is still wellbelow its target speed of 30 mph. Review of the analysis output shows that the intersection of CH 42and CH 23 (Cedar Avenue), which is expected to fail with these mitigations, is the major reason fornot meeting the target speed of this segment. It appears that if the intersection of CH 42 and CH 23(Cedar Avenue) operated at LOS D or better, the result would be operating speeds in Segment 13that meet or exceed the target speed.

6.6.3 Moderate Cost Geometry Summary

This analysis shows that for the most part pure roadway geometry improvements combined with thelow cost improvements (that add capacity to CH 42) discussed in Scenario 1 can come close tomeeting the traffic operation objectives of this project. However, it should be noted that some ofthe widening analyzed in this scenario may result in substantial land use impacts. For example,widening CH 42 between Elm Drive and Hayes Road would require the removal of frontage roadsalong CH 42 and would subsequently result in a number of homes being displaced. As a result of thepotential impacts associated with building-out CH 42, additional analysis will focus on alternativesto widening.

6.7 SCENARIO 2B: MODERATE COST SIGNAL REMOVAL

The purpose of this scenario is to determine the potential impact on traffic operations associated withremoving traffic signals in order to increase signal spacing. As noted in the literature search,increasing spacing between traffic signal has proven to be very effective in reducing congestion alonghigh-volume arterial roadways. This scenario should also help to determine the optimal spacingbetween traffic signals. In setting up this scenario there were questions as to how traffic would beredistributed from the removed traffic signals. Realizing that this is a variable issue, it was determinedthat two separate scenarios should be analyzed in order to determine a range of expected benefitwhen removing traffic signals. The first scenario accounted for all of the expected future traffic atall of the affected intersections and the second scenario is based on a reduction in traffic on theaffected minor street approaches.

6.7.1 Signal Removal Assumptions


This scenario involved several assumptions involving which signals should be removed from thecomputer model being used to analyze traffic operations in the CH 42 Corridor, the proposedgeometry of these intersections, and the redistribution of traffic from these intersections. This sectiondiscusses and documents each assumption.

Proposed Locations of Traffic Signals to be Removed

The first step in setting up this scenario was to determine the existing and assumed future trafficsignals that would be both beneficial and feasible to remove. The goal in removing traffic signals wasto obtain an optimum signal spacing for coordinated systems of approximately one-half mile. Usingthis criteria the Technical Committee determined the following signals should be tested for removalfrom the model of the corridor.

• CH 17 / Between CH 78 and CH 42 (Assumed) • CH 42 / Boone Avenue (Assumed) • CH 42 / Huntington Avenue (Inplace) • CH 42 / Burnsville Parkway (Inplace) • CH 42 / Judicial Road (Inplace) • CH 42 / Newton Avenue (Assumed) • CH 42 / Irving Avenue (Inplace) • CH 42 / Plymouth Avenue (Inplace) • CH 42 / Elm Drive (Inplace) • CH 42 / Hayes Road (Inplace) • CH 42 / Garrett Avenue (Inplace) • CH 42 / Foliage Avenue (Assumed) • CH 42 / McNamarra Drive (Assumed)

This list was later modified by replacing the removal of the Burnsville Parkway and Judicial Roadsignals with the removal of the CH 42 / Southcross Drive signal. This was done strictly because itwas determined in preliminary modeling that Southcross Drive would not have the capacity to serveall of the diverted traffic from the Burnsville Parkway and Judicial Road signals if CH 42 was tomaintain its four-lane cross section. Furthermore, where Burnsville Parkway and Judicial Roadmaintain approximately half mile spacing and are able to receive the benefits of signal interconnection,the next signalized intersections on either side of Southcross Drive are approximately three-quartersof a mile and, therefore, the benefits of signal interconnection are reduced.

Assumed Intersection Geometry for Signal Removal

The first assumption relative to the intersection geometry of locations where traffic signals areassumed to be removed is that full access should not be maintained. It was determined that a three-quarter access intersection should be developed at each of these locations. The direction of theallowed left turn at each intersection was chosen by determining which left turn was of greater


importance to the adjacent developments. This was determined from projected left turn volumes,alternative accessibility to adjacent developments, and connectivity of local roads. It should be notedthat in some cases it was determined that left turns in both directions was required to maintainreasonable accessibility to adjacent land uses. Table 6-12 and Table 6-13 show the changes assumedunder the two signal removal scenarios. The mitigations are illustrated in Figure 6-15.

Assumptions of Scenario with Diversions

With the removal of traffic signals and the corresponding reduction of access at these intersectionssome method of accounting for diverted traffic needed to be developed. This scenario accounts forevery vehicle by diverting the vehicles through the adjacent intersections. The method of divertingtraffic consisted of defining percentages of movements that would be diverted to each of the adjacentintersections by taking into account the function of the existing roads and the alternative accessibilityto those roads. By accounting for every vehicle this method of diverting traffic always increasedtraffic volumes as well as the percentage of turning vehicles at the adjacent signalized intersections.

This approach to accounting for all diverted traffic has some inherent assumptions regarding overallland use. For one, this method assumes that all traffic will not divert from its original path until it isthe immediate vicinity of its destination. This may be reasonable for a percentage of the divertedtraffic, however it would also be expected that some vehicles would divert from the main street(CH 42) farther away from the destination or choose a different route entirely, that does not includeusing CH 42 at all. This would result in the diverted traffic being spread throughout the roadwaynetwork and not concentrated in one area. A second assumption is that removing or not allowingaccess would not change the way a property is developed. This also doesn’t seem to be entirelyaccurate as it would be reasonable to expect that an adjacent parcel of land may develop with a landuse that doesn’t depend on as high a number of pass by trips. This would result in less trips beinggenerated by a particular site which in turn would reduce the overall vehicular demand in thatparticular area of the corridor.

Assumptions of Scenario with No Diversions

As discussed previously, accounting for the diversion of every vehicle when removing a traffic signalappears to be overly conservative. Furthermore, trying to determine the exact effect of removingaccess is difficult to predict. Therefore, this additional scenario was analyzed to show an expectedrange of impact when traffic signals are removed.

The first scenario is likely to predict the least expected benefit of removing traffic signals as itaccounts for every diverted vehicle. This scenario models the maximum expected benefit that can beexpected when traffic signals are removed. This is achieved by removing all diverted traffic from thenetwork. Therefore when a signal is removed the remaining signals do not have an increase in turningmovement volume.6.7.2 Signal Removal Traffic Operations Analysis



Table 6-4 lists the intersection LOS and delay results for the two signal removal scenarios. Theseresults show that for the signal removal with diversions scenario that several intersections have slightincreases in LOS from the low cost scenario. The results also show that the intersection of PortlandAve and CH 42 is now expected to operate at level of service E. The increase in level of service atthese intersections is caused by vehicles diverted from intersections where traffic signals are removed.

The results of the signal removal with no diversions show that there is little to no change inintersection delay at all intersections.


Table 6-5 lists the arterial roadway speed and level of service for each segment for both signalremoval scenarios. The results of the signal removal with diversions scenario show that somesegments are expected to have slight increases in arterial speed and some segments are expected tohave slight decreases in arterial speed from the low cost scenario. In both cases the maximumexpected change in arterial speed is two miles per hour. Review of the analysis output shows thatintersections that have increased turning movement volumes due to vehicle diversions are the primarycause of decreased arterial speeds. This is supported by the increase in vehicle delay shown at manyof these intersections.

The results of the signal removal with no diversions scenario show that more than half of thesegments show a slight increase in arterial speed. The largest expected increase of 3 mph was seenin Segment 12 (Southcross Drive to Pennock Avenue).

Measures of Effectiveness

Table 6-14 lists several measures of effectiveness results for the low cost scenario and both signalremoval scenarios. These measures of effectiveness are shown because the benefits of removingsignals are not limited to arterial travel speed.

The results show that for each of the three measures of effectiveness (signal delay, number of stops,and fuel consumed) that the signal removal with diversions scenario generally shows improvementsover the low cost scenario. Results are only for the intersections along CH 42 and include both mainstreet and minor street approaches. In some instances the improvement is quite significant and in afew cases the measures of effectiveness are expected to get worse.

The results also show that the signal removal with no diversions scenario yields improvement forevery measure of effectiveness in every segment. In many of these cases the improvement is quitesignificant.

6.7.3 Signal Removal Summary


The results of this scenario show that expected impact of removing traffic signals varies dependingon the assumptions made in diverting traffic. With the most conservative approach to diverting trafficthe results showed that in general traffic operations improved when traffic signals were removed. However, there were a few cases where traffic operations became slightly worse. As statedpreviously this is mainly due to the diverted traffic increasing turning movement volumes at adjacentintersections and therefore decreasing the intersection’s level of service. This is an important pointas it is clear that a project that includes signal removal should closely evaluate the effects that thesignal removal has on other intersections and provide mitigations to these intersections as necessary.

One way to gradually phase in the concept of removing traffic signals from operation would be todevelop and initiate a new traffic signal timing strategy for the corridor. This strategy wouldemphasize the priority placed on mainline mobility by assigning higher percentages of the signal cycleto CH 42 in order to offset forecast increases in traffic volume and congestion. The ultimateextension of this strategy would be to, where necessary, effectively assign 100 percent of the signalcycle to CH 42 by removing some traffic signals.

The results of this scenario also show that with a less conservative method of dealing with divertedtraffic, that traffic operations will significantly improve in the segments with signal removals. Dueto these results it is expected that, if traffic signals are removed and the appropriate mitigations aremade in order to deal with diverted traffic, removing traffic signals will improve traffic operations. As a result, the locations where traffic signals were removed in this scenario will remain unsignalizedas the modeling process continues and higher cost mitigations are evaluated.

6.8 SCENARIO 3: HIGH COST MITIGATIONS

The purpose of this scenario is to look at possible high cost mitigations that could be used as analternative to the geometry mitigations in scenario 2A in order to meet the speed and level of servicegoals of the corridor. In keeping with the results of Scenario 2B, one of the criteria in selectingalternative high cost improvements was to try and attain half-mile spacing between signals. As partof this scenario all mitigations from Scenario 1 and Scenario 2B-1 are being used as a base for thisanalysis. All of the high cost mitigations evaluated in this scenario are located between CH 31 inScott County and CH 31 (Pilot Knob Road) in Dakota County. As a result, only this section ofroadway will be discussed and analyzed in this section.

6.8.1 High Cost Mitigations

Figure 6-16 gives an overview of the mitigations used in this scenario and Table 6-15 lists thedifferent types of mitigations used in this scenario and the intersections in which they wereimplemented. What follows is a short description of each mitigation.


Grade Separation of CH 42 and CH 5 - From the previous analysis it is apparent that theintersection of CH 5 and CH 42 needs to be mitigated in some way in order to operate at anacceptable level in the Year 2020. In Scenario 2A, CH 42 was widened to a 6-lane cross section inorder to mitigate the expected congestion. As an alternative to that solution this scenario evaluatesa grade separation of CH 42 and CH 5. The grade separation would involve a CH 42 overpass ofCH 5 with an urban single-point interchange on CH 5. A typical diamond interchange is shown inFigure 6-17 and a single-point urban interchange is shown in Figure 6-18.

Grade Separation of CH 42 and Aldrich Avenue - With the Supporting Roadway Scenarioincluding a half-diamond at I-35W/CH 38 (McAndrews Road), it is expected that the preferredmethod of entering Burnsville Center from the north will be to exit from I-35W at CH 38(McAndrews Road) and then to continue on Aldrich into Burnsville Center. This mitigation involvesgrade separating CH 42 and Aldrich Avenue with a CH 42 overpass of Aldrich. Access between CH42 and Aldrich would be via the right-in/right-out access points to the west of Aldrich on CH 42, asshown in Figure 6-19. This mitigation would also likely require the installation of traffic signals atthe intersection of the access roads with Aldrich to both the north and south of CH 42.

Connection from I-35E to I-35W - This mitigation involves eliminating the left turn from eastboundCH 42 to northbound I-35W by diverting this turning traffic east on CH 42 and building a connectionbetween the southbound ramp from CH 42 to I-35E to northbound I-35W. This loop connectionwould be built in the area between I-35W, I-35E, and CH 42, as shown in Figure 6-20. The benefitof this mitigation is two-fold. First, it would allow the signal at CH 42 and the East Ramp of I-35Wto be removed by rerouting the left turns through the intersection of CH 42 and Nicollet Avenue andonto the proposed ramp. Second, it would greatly increase the storage capacity of the ramps tonorthbound I-35W. This is an important benefit as currently the queues from the ramp metering atthis location often back traffic up onto CH 42.

Combine I-35E Ramps into Single-Point Urban Interchange - This mitigation involves combiningthe existing signals at the east and west ramps of I-35E with a single-point urban interchange. Dueto the expected high volumes of right turns from southbound I-35E to westbound CH 42, thismitigation also includes triple right turn lanes with a right turn overlap for this movement.

Grade Separation of CH 42 and CH 23 (Cedar Avenue) - This mitigation involves gradeseparating CH 42 and CH 23 (Cedar Avenue) with a CH 23 (Cedar Avenue) overpass of CH 42 andsingle-point urban interchange on CH 42. With this mitigation CH 23 (Cedar Avenue) wouldmaintain the present 6-lane cross section and CH 42 would maintain the 4-lane cross section.

Grade Separation of CH 42 and CH 31 (Pilot Knob Road) - This mitigation involves gradeseparating CH 42 and CH 31 with a CH 42 overpass of CH 31 (Pilot Knob Road) and a single-pointurban interchange on CH 31 (Pilot Knob Road). With this mitigation CH 42 and CH 31 (Pilot KnobRoad) would both maintain their 4-lane cross sections.

6.8.2 High Cost Mitigation Traffic Operations Analysis



Table 6-4 lists the intersection level of service and delay results for the high cost scenario. Theseresults show significant improvements in intersection level of service and delay for over one half theintersections analyzed in this scenario. In fact six intersections that were previously expected to failin the signal removal with diversions scenario are now expected to operate at level of service D orbetter. Most notably the intersection of CH 42 and CH 23 (Cedar Avenue), which has been expectedto fail in all previous scenarios, is expected to operate at LOS D if it is grade separated. The onlyintersection in this scenario that is now expected to operate worse than level of service D is theintersection of CR 11 and CH 42. It appears that this is primarily due to volumes at this intersectionthat suggest the need for a 6-lane cross section on CH 42.


Table 6-5 lists the arterial roadway speed and level of service for each segment of the high costscenario. These results show significant increases in expected arterial speed for four of the segmentsincluded in this scenario. Further review of the results shows that two of these segments [Segments8 (CR 31 to Irving Avenue) and 9 (Irving Avenue to I-35W)] now meet or exceed their target speedsand Segment 10 is close to its target speed. With these high cost mitigations Segments 11 and 13 arethe only segments which are not close to meeting their target speeds.

6.8.3 High Cost Mitigations Summary

The high cost mitigations in this scenario analyzed the grade separation of several major intersectionsalong the CH 42 corridor as well as several interchange improvements at I-35E and I-35W. Thesemitigations were analyzed as potential alternatives to adding capacity by widening CH 42. Thecomparison of the two scenarios shows similar results as both scenarios come close to meeting thetraffic operations objectives of the project. It is clear from these results and the different types ofmitigations analyzed in each scenario that some combination of the two scenarios is likely to produceresults that meet the traffic operation objectives for the project.

6.9 SCENARIO 4: COMBINED MITIGATIONS

The purpose of this scenario is to combine the most practical/feasible mitigations from Scenario 2A(Moderate Cost Geometry) and Scenario 3 (High Cost) in order to determine a scenario which meetsthe speed and level of service goals of the corridor as well as well as being a feasible long termsolution. Like Scenario 3, this scenario uses one-half mile spacing as a goal for spacing betweensignals. This scenario also includes all mitigations from Scenario 1 (Low Cost) and Scenario 2B.1(Moderate Cost Signal Removal) as a base for the analysis.


6.9.1 Combined Mitigations

Figure 6-21 gives an overview of the mitigations used in this scenario and Table 6-16 lists thedifferent types of mitigations used in this scenario and the intersections in which they wereimplemented. What follows is a short description and explanation of each mitigation.

Extension of 6-lane cross section to west of Burnsville Parkway - From previous analyses it isapparent that the intersection of CH 5 and CH 42 needs to be mitigated in some way in order tooperate at an acceptable level in the year 2020. In Scenario 2A (Moderate Cost Geometry) CH 42was widened to a 6-lane cross section with dual left turn lanes and in Scenario 3 (High Cost) theintersection was grade-separated with a single-point urban interchange on CH 5. Under bothscenarios traffic operations significantly improve and the intersection is expected to operate at LOS Cor better.

Due to the existing land use conditions adjacent to the intersection, it appears that providing thewidening described in scenario 2A is more feasible than building the single-point urban interchangedescribed in Scenario 3 as it would have less impact on adjoining properties. It was also determinedthat if CH 42 was widened to the west of CH 5, the construction was likely to impact the existingbridge over the railroad tracks. With this impact it was further determined that the appropriatemitigation to analyze was extending the 6-lane cross section on CH 42 to west of Burnsville Parkway. This would also address previously noted operational deficiencies at a signalized CH 42/SouthcrossDrive intersection.

Grade Separation of CH 42 and Aldrich Avenue - This is the same mitigation evaluated inScenario 3. As before, this mitigation involves grade separating CH 42 and Aldrich Avenue with aCH 42 overpass of Aldrich. Access between CH 42 and Aldrich would be via the right in/right outaccesses to the west of Aldrich on CH 42. This mitigation would also probably require theinstallation of traffic signals at the intersection of the access roads with Aldrich to both the north andsouth of CH 42.

Connection from I-35E to I-35W - This is also a mitigation that was evaluated in Scenario 3. Aspreviously stated it involves diverting the eastbound CH 42 to northbound I-35W left turn buildinga connection between the southbound on ramp from CH 42 to I-35E to northbound I-35W. Thisloop connection could be built in the area between I-35W, I-35E, and CH 42.Combine I-35E Ramps into Single-Point Diamond - This is another mitigation that was evaluatedin Scenario 3. As before, it involves combining the existing signals at the east and west ramps of I-35E with a single-point urban interchange. It also includes triple-right turn lanes with a right turnoverlap for this movement.

Grade Separation of CH 42 and CH 23 (Cedar Avenue) - In Scenario 2A it was determined thatthe intersection of CH 42 and CH 23 (Cedar Avenue) failed with a 6-lane cross section on CH 42 anda 8-lane cross section on CH 23 (Cedar Avenue). It was also determined separately that it would


require 9 lanes of approach on CH 23 (Cedar Avenue) and 7 lanes on CH 42 in order for theintersection to operate at LOS D or better.

In Scenario 3 it was determined that if this intersection was grade separated, the new intersectionwould operate at LOS D or better without having to increase the cross section of either roadway. Due to the extensive roadway widening that would be required at this intersection to operatereasonably, it appears that grade separating this intersection would have the least overall impacts andis the more feasible solution. As a result this analysis will model the same mitigation as Scenario 3in which CH 42 and CH 23 (Cedar Avenue) are grade-separated with a single-point urban interchangeon CH 42.

6-Lane Cross Section East of CH 23 (Cedar Avenue) to East of CH 31 (Pilot Knob Road) - InScenario 2A it was determined that a 6-lane cross section between CH 23 (Cedar Avenue) and CH31 (Pilot Knob Road) significantly improved operations in this segment. It was also shown inScenario 3 that the grade separation of the CH 42/CH 23 (Cedar Avenue) intersections and CH 42and CH 31 (Pilot Knob Road) improved operations. However, neither scenario was able to meet thespeed objectives for this segment of roadway.

Scenario 2A failed to show improved operations primarily because the intersection of CH 42 and CH23 (Cedar Avenue) failed with an at-grade intersection. Scenario 3 failed to meet the speedobjectives mainly because the remaining at-grade intersections operate at or near capacity with onlya 4-lane cross section on CH 42. This is due to the high volume of through traffic in this segmentwhich seems to warrant a 6-lane cross section. With the grade separation of CH 42 and CH 23(Cedar Avenue) it would seem likely that this segment could come close to its speed objective if theremaining section of roadway was widened to a 6-lane section. Furthermore, widening CH 42 eastof CH 23 (Cedar Avenue) seems to be a feasible alternative as the commercial build-out of CH 42has yet to proceed east of Galaxie. As a result in conjunction with the grade separation of CH 42 andCH 23 (Cedar Avenue) this analysis modeled a 6-lane cross section from west of CH 23 (CedarAvenue) to west of CH 31 (Pilot Knob Road).

Extension of 4-Lane Cross Section from TH 52 to existing TH 55 with Single-Point UrbanInterchange at TH 52 Ramps - This mitigation includes extending the 4-lane cross section on CH42 from west of TH 52 to the existing intersection of CH 42 with TH 55. This mitigation is beingconsidered because the rerouting of TH 55 as detailed in the supporting roadway improvementswould greatly increase the projected traffic volumes (8,900 to 23,500 AADT) on this segment of CH42. The higher traffic volume suggests the need for a 4-lane roadway on this segment.

This mitigation also includes a single-point urban interchange at CH 42 and TH 52. This is includedbecause the close proximity of the existing TH 52 bridge piers at CH 42 would prevent the wideningof CH 42. As a result, any widening of CH 42 would require the construction of a new interchange. It was determined that a single-point urban interchange was preferable to a typical diamondinterchange because it would provide better intersection spacing when frontage roads are added toTH 52.


6.9.2 Combined Mitigations Traffic Operations Analysis


Table 6-4 lists the intersection level of service and delay results for the combined scenario. Theseresults show that every intersection is expected to operate at LOS D or better with these mitigations. Most notably the intersection of CH 42 and CR 11, which had failed in the high cost scenario, isexpected to operate at LOS D when the 6-lane cross section is extended through the intersection.


Table 6-5 lists the arterial roadway speed and level of service for each segment of the combinedmitigations scenario. These results show expected speeds that are generally better than both themoderate cost geometry scenario and the high cost scenario. Furthermore, each segment is close tomeeting the speed objective set for it and the overall weighted average speed for the corridor is thesame as the existing condition.

6.9.3 Combined Mitigations Summary

The mitigations described in this scenario produce expected traffic operation results that meet theobjectives adopted by the Technical and Advisory Committees. In order to meet the objectives avariety of mitigations were considered. These mitigations included the Supporting Roadway Systemand a variety of geometry, signal phasing, signal interconnect, signal removal, lane additions, gradeseparations, and interchange improvements.

6.10 PRELIMINARY RECOMMENDED ROADWAY IMPROVEMENTS

The purpose of this final scenario is to produce results from the traffic operations model that includesall of the recommended traffic mitigations. This scenario includes several changes that were madeto Scenario 4 due to additional analysis of several alternatives.

6.10.1 Preliminary Recommended Roadway Improvements

There were three basic changes that were made to the scenario 4 model in order to develop thepreliminary recommended roadway improvements. Each of the three alternatives was analyzed withrespect to scenario 4 and each was determined to be a preferable mitigation. The preliminaryrecommended roadway improvements are summarized in Table 6-17 and illustrated in Figure 6-22.The following describes each alternative and discusses the reasoning for including the alternative inthe recommended model.


Phasing Adjustment at I-35W West Ramp - This mitigation involves revising the phasing at CH 42and I-35W West Ramp in order to give the eastbound through movement a green indication at thesame time that the right turn movement off the I-35W ramp is given an exclusive right turn indication. This requires adding an additional lane to the I-35W ramp approach and reassigning the lanes ofapproach so there are two exclusive right turn lanes and no shared through right lanes.

The benefit of this mitigation is that it shares some of the time that the large volume of right turningtraffic off the I-35W ramp requires with the high volume eastbound through movement. A test of thisalternative showed that this mitigation increased the expected speed in Segment 9 and reduced theexpected delay at the CH 42 and I-35W west ramp intersection. This mitigation also had the furtherbenefit of reducing the required cycle length of the signal interconnect system that includes signalsfrom CH 5 to Portland Avenue. This resulted in better signal operation at several of the intersectionwithin the interconnect system.

No Connection from I-35E to I-35W - This scenario evaluated keeping the I-35W East Ramp signalin place as opposed to making the connection between the I-35E southbound on ramp and I-35W. This was done since the I-35W East Ramp signal only has to serve two phases and never stops theeastbound CH 42 traffic. As a result, this signal has only a small effect on the CH 42 operatingspeeds. Furthermore, removing the west ramp signal and building the loop connection addedapproximately 500 vehicles to the already congested eastbound through movement at the CH 42 andNicollet Avenue intersection.

The comparison of keeping the signal in place versus building the loop connection showed that therewas little difference in the traffic operations of either alternative. As a result, leaving the signal in atthe I-35W west ramp was determined to be the preferred method as the costly construction of the I-35E to I-35W loop could be avoided. It should be noted that the loop connection could still be afeasible option for increasing the vehicle storage required by the ramp metering at the I-35W westramp.

Signalize Burnsville Parkway and Judicial Road as Opposed to Southcross Drive - In theanalysis of the signal removal scenario it was determined that CH 42 operated better with signals atBurnsville Parkway and Judicial Road as opposed to Southcross Drive. This was the direct result ofthe large number of diversions from the Burnsville Parkway and Judicial Road intersections causingthe Southcross Drive and CH 42 intersection to fail.As a result of this analysis it was determined that the recommended scenario should include signalized intersections for CH 42 with Burnsville Parkway and Judicial Road and the CH 42 andSouthcross Drive intersection should be modified to provide three-quarter access to both the northand south. It is also part of this recommendation that at no point should all three intersections besignalized simultaneously. Another option could be the combination of signalized intersections of CH42 at Southcross Drive and Burnsville Parkway with three-quarter access at Judicial Road andHuntington Avenue. If this option is explored, further analysis will be required. In addition, it willnecessitate the construction of supporting roadways between Huntington Avenue and CH 5.


6.10.2 Preliminary Recommended Roadway Improvements Traffic Operations Analysis


Table 6-4 lists the intersection level of service and delay results for the preliminary recommendedscenario. These results show that every intersection is expected to operate at LOS D or better withthese recommended mitigations. The results also show that four intersections are expected to operatewith less intersection delay and two intersections are expected to operate with higher intersectiondelay than in the combined mitigation scenario due to the revised mitigations.


Table 6-5 lists the arterial roadway speed and level of service for each segment of the preliminaryrecommended roadway improvement scenario. These results show that the expected speed for eachsegment is close to meeting the speed objective set for that segment. Furthermore, the overallweighted average speed for the corridor is the same as the existing condition. These results alsoshow that Segments 8, 9, and 11 have higher expected speeds than they did in the combinedmitigation scenario due to the revised mitigations.

6.10.3 Preliminary Recommended Roadway Improvements Summary

This preliminary recommended roadway improvement scenario included all of the recommendedtraffic operation mitigations identified in this analysis. The mitigations include the supportingroadway improvements and a variety of geometry, signal phasing, signal interconnect, signal removal,lane additions, grade separations, and interchange improvements. The modeling of this scenarioshows that these mitigations are capable of relieving a significant portion of the expected congestionon CH 42. Furthermore, these mitigations enable the corridor to meet the speed and LOS objectivesset for it.

A summary of the preliminary recommended traffic operation mitigations is as follows:

• All of the supporting roadway improvements described in the Supporting Roadway Scenarioand that were determined to provide a high level of traffic diversion from CH 42 and that hada high probably of implementation are included in the recommended plan. These supportingroadway improvements include the 150th Street/Crystal Lake Road Extension, theMcAndrews Road/I-35W Interchange, the McAndrews Road Extension, the ConnellyParkway Extension, the 147th Street and 153rd Street Extensions, the 140th Street Extension,the rerouting of TH 55, and the CH 21 Extension.


• All low cost improvements described in Scenario 2 and detailed in Table 6-10 are consideredpart of the recommended plan. These improvements include cross street lane additions,mainline right turn lanes, signal phasing modifications, and signal coordination.

• Several traffic signals along the corridor are recommended to be removed and the intersectiongeometry at these intersection modified to three-quarter access. These intersections includethe intersection of CH 42 with Huntington Avenue, Burnsville Parkway, Judicial Road, IrvingAvenue, Plymouth Avenue, Elm Drive, Hayes Road, and Garrett Avenue.

• Varies segments of CH 42 are recommended to be widened from their existing cross sections. The 6-lane cross section on CH 42 is recommended to be extended from Irving Avenue westto Burnsville Parkway and from Plymouth Avenue to east of CR 11. It is also recommendedthat CH 42 should be widened to a 6-lane cross section from Garrett Avenue to east of CH31 (Pilot Knob Road). A further recommendation is that with the rerouting of TH 55, CH42 should be widened to a 4-lane cross section between TH 52 and its existing intersectionwith TH 55. Along with upgrading these sections of CH 42, various geometry improvementsthat include widening to roadways intersecting CH 42 and the addition of dual lefts atintersections were also recommended. These mitigations are documented in Table 6-17.

• The final type of recommended mitigation is grade separation and interchange realignment. The recommended plan includes the grade separation of Aldrich Avenue and CH 42 asshown in Figure 6-19, the combining of the ramps at I-35E into a single-point urbaninterchange, the grade separation of CH 42 and CH 23 (Cedar Avenue) with a single-pointurban interchange on CH 42, and a single-point urban interchange of CH 42 and TH 52.

It should be noted that this document is an overall blueprint to guide roadway improvements withinthe CH 42 Corridor. These blueprint recommendations are to meet the goals and objectivesdeveloped during the study process. As individual projects are considered for implementation bystate, county or local jurisdictions, the results of this study will be supplemented with additional dataand analysis to support detailed project planning and design as needed. Actual projects will provideopportunities for public and local review. During project development, other options may beidentified that meet the mobility and access goals in the CH 42 Corridor.

As described above, the preliminary recommended mitigations analyzed in this scenario involve avariety of improvements. The specific improvements that have become part of this preliminaryrecommended plan were developed primarily through traffic operations analysis. The feasibility ofthe improvements was also taken into account when several different mitigations were considered. These preliminary recommendations will be reviewed in the following chapter on environmentalissues and their land use impacts will also be considered before the final recommendations for thecorridor are outlined in Chapter 8.0.

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