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1

MAPA-D2(105), CN 22547

Sarpy County I-80 Interchange Assessment

April 2017

Introduction

This Sub-Area operations assessment memorandum details the potential need for a new

interchange along I-80 in Sarpy County. The premise for this evaluation is the assumption that a

new interchange will not be approved for I-80 unless it is shown that the adjacent interchanges

will not be able to serve future traffic demands. This traffic operations assessment was

conducted for ramp terminals at N-31, N-370, and N-50.

Methodologies

Study Area Network

As directed by the Management Team, the roadway network used to develop future year traffic

volumes is shown in Figure 1. This roadway network included all projects selected for the Metro

Area Travel Improvement Study (MTIS) preferred regional strategy package with the addition of

two non-MTIS projects on Schram Road and Capehart Road. It was determined through

technical analyses and discussions with MAPA and Sarpy County staff that these non-MTIS

projects would be required to support mobility in the area given the development growth.

Volume Development

Traffic counts were collected from NDOR at the N-31, N-370, and N-50 interchanges and at

adjacent intersections. The traffic volumes were evaluated and balanced along each corridor for

the AM and PM peak hours. Peak hour volumes were developed using existing segment

Average Daily Traffic (ADT) in combination with the Metro Area Planning Agency (MAPA) 2040

travel demand model output. Peak hour volumes are shown in the analysis figures in the

appendix.

2

Figure 1. Study Area Network

Level of Service

Level of Service (LOS) analyses for the ramp terminal intersections were performed using

procedures from Chapter 18 procedures of the Highway Capacity Manual 2010 Edition (HCM

2010). Highway Capacity Software 2010 (HCS 2010) version 6.50, a computerized analytical

tool based on the HCM, was utilized for the intersection operational analysis. LOS for signalized

intersections is evaluated based on control delay per vehicle (in seconds per vehicle).

Note that the HCM 2010 does not have a standard methodology to analyze all types of

interchange configurations. A supplemental methodology was developed by the consultant team

that analyzes a Diverging Diamond Interchange (DDI) by redistributing traffic at the ramp

terminals to replicate the non-conflicting left and right turns that occur at the interchange.

Signalized intersection LOS delay thresholds are shown in Table 1.

3

Table 1. Delay Thresholds for Signalized Intersections

LOS Control Delay

(seconds/vehicle)

A <10

B >10-20

C >20-35

D >35-55

E >55-80

F >80

Results

LOS performance measure targets have been established for MTIS. The threshold for

acceptable HCM operations for the overall intersection is LOS ‘D’ or better. The threshold for

acceptable HCM operations for individual movements at each intersection is LOS ‘E’ or better. If

the overall intersection or individual movement LOS thresholds are not met, they are noted in

the analysis figures by highlighting the intersection or individual movement in red text. Note that

all lane configurations for the analysis interchanges can be found in the appendix.

Year 2040 Without 180th/192nd Interchange Traffic Operations

This section covers traffic operations at the existing interchanges in the sub-area. It is assumed

that all projects shown in Figure 1 are complete except the 180th/192nd interchange.

No-Build Traffic Operations

The HCM LOS results for the No-Build Traffic Operations are shown in Table 2. Note that the

planned widening projects included in Figure 1 are assumed to be in place for the no-build

scenario. For example, N-370 is assumed to be widened to a 6 lane section through the

interchange with the number of turn lanes that exist today staying the same.

Table 2. Year 2040 No-Build Operations without 180th

/192nd

Interchange HCM LOS

Intersection AM LOS PM LOS

N-31 & I-80 WB B E*

N-31 & I-80 EB E* E*

N-370 & I-80 WB F* F*

N-370 & I-80 EB F* F*

N-50 & I-80 WB E* D*

N-50 & I-80 EB B* D*

* Failing Individual Movement(s)

Note that the No-Build HCM LOS for N-31 assumes re-striping the WB off-ramp to dual rights.

4

Build Traffic Operations

This section’s purpose is to address the deficiencies identified in the No-Build without

180th/192nd Interchange section through various interchange reconfigurations including:

• Diamond Interchange Expansion (through additional turn lanes)

• Diverging Diamond Interchange (DDI)

• Partial Cloverleaf Interchange (Parclo)

The HCM LOS results for the interchange reconfigurations are shown in Table 3.

Table 3. Year 2040 Interchange Reconfiguration Operations without 180th

/192nd

Interchange HCM LOS

Intersection

Diamond Interchange Expansion

Diverging Diamond Interchange

Partial Cloverleaf Interchange

AM LOS PM LOS AM LOS PM LOS AM LOS PM LOS

N-31 & I-80 WB C C B B C C

N-31 & I-80 EB F* D B B F* C

N-370 & I-80 WB F* F* E* D* F* F*

N-370 & I-80 EB F* E* B B B B

N-50 & I-80 WB C B C B B C

N-50 & I-80 EB B C C B B B


Year 2040 without 180th/192nd Interchange Summary

• N-31: A DDI will be needed to provide acceptable LOS in 2040. See Figure A5 for lane

configurations and LOS.

• N-370: A DDI configuration provides the best LOS compared to the other interchange

configurations in 2040. Failing movements exist at the interchange and overall

intersection LOS ‘E’ exists in the AM peak hour. See Figure A8 for lane configurations

and LOS.

• N-50: A standard diamond, Parclo, and DDI all provide acceptable LOS in 2040, but a

DDI will provide a longer operational life. See Figures A10, A11, and A12 for lane

configurations and LOS.

5

Year 2040 Traffic Operations with 180th/192nd Interchange

This section covers traffic operations at the existing interchanges and the proposed 180th/192nd

interchange. It is assumed that all projects shown in Figure 1 are complete including the

180th/192nd interchange.

Average Daily Traffic Comparison

Year 2040 forecasted ADTs were compared at the service interchanges between the (with and

without) 180th/192nd Interchange scenarios. The 2040 forecasts are shown in Figure 2.

Figure 2. Year 2040 ADT Forecast Comparison

6

No-Build Traffic Operations

The HCM LOS results for the No-Build Traffic Operations are shown in Table 4.

Table 4. Year 2040 No-Build Operations with 180th

/192nd

Interchange HCM LOS

Intersection AM LOS PM LOS

N-31 & I-80 WB A C

N-31 & I-80 EB B C

N-370 & I-80 WB F* F*

N-370 & I-80 EB F* F*

N-50 & I-80 WB E* D*

N-50 & I-80 EB C* C*


Build Traffic Operations

The HCM LOS results for the interchange reconfigurations are shown in Table 5.

Table 5. Year 2040 Interchange Reconfiguration Operations with 180th

/192nd

Interchange HCM LOS

Intersection

Diamond Interchange Expansion

Diverging Diamond Interchange

Partial Cloverleaf Interchange

AM LOS PM LOS AM LOS PM LOS AM LOS PM LOS

N-370 & I-80 WB E* E* B C D* C

N-370 & I-80 EB F* F* B B B B

N-50 & I-80 WB B B B B B C

N-50 & I-80 EB B C B B B B

180th/192nd & I-80 WB

A C B B A C

180th/192nd & I-80 EB

C B B B A A


Note that the N-31 interchange was not analyzed with interchange reconfigurations since the

existing configuration provides acceptable LOS.

7

Year 2040 with 180th/192nd Interchange Summary

• The 180th/192nd Interchange primarily relieves congestion on N-31 & N-370

o The 180th/192nd Interchange pulls enough daily traffic from N-31 to minimize the

need for a 6 lane widening from N-370 to US-6 from the MTIS preferred regional

strategy package.

• Interchange Fixes

o N-31: No reconstruction will be needed at the N-31 interchange to accommodate

Year 2040 peak hour volumes. See Figure A13 for lane configurations and LOS.

o N-370: A DDI will be needed to provide acceptable LOS in 2040. See

Figure A17 for lane configurations and LOS.

o N-50: A standard diamond, Parclo, and DDI all provide acceptable LOS in 2040.

See Figures A19, A20, and A21 for lane configurations and LOS.

• 180th/192nd New Interchange: A standard diamond, DDI, and Parclo all provide

acceptable LOS. See Figures A22, A23, and A24 for lane configurations and LOS.

Next Steps

This traffic operations assessment identified the need for a new interchange between N-370 and

N-31 along I-80. However, a more detailed Interchange Justification Report (IJR) would be

required for a new interchange on I-80.

8

Appendix

Year 2040 without 180th/192nd Interchange

• Figure A1: N-31 No-Build



• Figure A4: N-31 Build Diamond Interchange Expansion

• Figure A5: N-31 Build DDI

• Figure A6: N-31 Build Parclo







Year 2040 with 180th/192nd Interchange










• Figure A22: 180th/192nd New Interchange (Diamond Configuration)

• Figure A23: 180th/192nd New Interchange (DDI Configuration)

• Figure A24: 180th/192nd New Interchange (Parclo Configuration)

(395) (1170) 635 (1415)

965 1655 0 (0)

175 (345)

230 620

(195) (1330)

(655) (860)

505 1325

(1050) 370

(0) 0 480 345

(195) 120 (475) (345)

A1

April 2017

Notes: 1. LOS 'F' movements shown in Red2. LOS may be worse due to metered volumes upstream.

Sources: 1. Traffic Volumes - Developed by HDR using MAPA 2040 Travel Model (February 2017).2. Traffic Capacity Analysis (HCS 2010) - Conducted by HDR (February 2017).

Date

Figure

B

E

EE

Not to Scale

´LEGEND

XXX (XXX) AM and (PM) Peak Hour Volumes

Intersection Lane Geometrics

AM Peak Hour Signalized Intersection Level of Service

PM Peak Hour Signalized Intersection Level of Service

X

X

*Restripe existing dual lefts and single right to a single left and dual rights.



N-31 No-Build Traffic Volumes and Operations Analysis Results

Sarpy County, NE

(2130) (0) (50)

905 0 85 1500 (2240) 35 (65)

350 (365) 1765 (2265)

(2535) 4140 (1015) 2125

(305) 265 (1570) 2100 85 0 370

(340) (0) (480)

A2

April 2017



Date

Figure

Not to Scale

´

F

F

F

F

LEGEND





X

X




Sarpy County, NE

(405) (1895) 545 (765)

380 2200 0 (0)

955 (945)

30 1465

(55) (1755)

(2080) (760)

2265 890

(405) 345

(0) 0 1150 1080

(60) 100 (1405) (940)

A3

April 2017



Date

Figure

E

D

BD

Not to Scale

´LEGEND





X

X




Sarpy County, NE

(395) (1170) 635 (1415)

965 1655 0 (0)

175 (345)

230 620

(195) (1330)

(655) (860)

505 1325

(1050) 370

(0) 0 480 345

(195) 120 (475) (345)

April 2017

A4



Date

Figure

C

F

CD

Not to Scale

´LEGEND





X

X



N-31 Build Diamond Interchange ExpansionTraffic Volumes and Operations Analysis Results

Sarpy County, NE

(395) (1170)

965 1655

635 (1415)

175 (345)

230 620

(195) (1330)

(655) (860)

505 1325

(1050) 370

(195) 120

480 345

(475) (345)

A5

April 2017



Date

Figure

Not to Scale

´LEGEND





X

X

B

B

B

B



N-31 Build Diverging Diamond Interchange Traffic Volumes and Operations Analysis Results

Sarpy County, NE

(395) (1170) 635 (1415)

965 1655 0 (0)

175 (345)

230 620

(195) (1330)

(860) (655)

1325 505

(1050) 370

(195) 120 480 345

(475) (345)

April 2017

A6



Date

Figure

C

F

Not to Scale

´LEGEND





X

X

C

C



N-31 Build Partial Cloverleaf InterchangeTraffic Volumes and Operations Analysis Results

Sarpy County, NE

(2130) (0) (50)

905 0 85 1500 (2240) 35 (65)

350 (365) 1765 (2265)

(2535) 4140 (1015) 2125

(305) 265 (1570) 2100 85 0 370

(340) (0) (480)

A7

April 2017



Date

Figure

Not to Scale

´

F

F

F

E

LEGEND





X

X




Sarpy County, NE

(2130) (50)

905 85 (1015) 2125 35 (65)

(1570) 2100 1765 (2265)

(2535) 4140 1500 (2240)

(305) 265 350 (365) 85 370

(340) (480)

April 2017

A8



Date

Figure

Not to Scale

´LEGEND





X

X

E

DB

B




Sarpy County, NE

(2130) (50)

905 85 350 (365) 35 (65)

1500 (2240) 1765 (2265)

(2535) 4140 (1570) 2100

(305) 265 (1015) 2125 85 370

(340) (480)

April 2017

A9



Date

Figure

Not to Scale

´

F

F

LEGEND





X

X




Sarpy County, NE

B

B

(405) (1895) 545 (765)

380 2200 0 (0)

955 (945)

30 1465

(55) (1755)

(2080) (760)

2265 890

(405) 345

(0) 0 1150 1080

(60) 100 (1405) (940)

A10

April 2017



Date

Figure

C

B

BC

Not to Scale

´LEGEND





X

X




Sarpy County, NE

(405) (1895)

380 2200

545 (765)

955 (945)

30 1465

(55) (1755)

(2080) (760)

2265 890

(405) 345

(60) 100

1150 1080

(1405) (940)

A11

April 2017



Date

Figure

Not to Scale

´LEGEND





X

X

C

B

C

B




Sarpy County, NE

(405) (1895) 545 (765)

380 2200 0 (0)

955 (945)

30 1465

(55) (1755)

(760) (2080)

890 2265

(405) 345

(60) 100 1150 1080

(1405) (940)

April 2017

A12



Date

Figure

B

C

Not to Scale

´LEGEND





X

X

B

B




Sarpy County, NE

(315) (870) 395 (915)

790 1185 0 (0)

125 (245)

190 520

(165) (1120)

(615) (500)

505 805

(900) 320

(0) 0 390 275

(165) 100 (385) (275)

A13

April 2017



Date

Figure

A

C

BC

Not to Scale

´LEGEND





X

X

*Restripe existing dual lefts and single right to a single left and dual rights.




Sarpy County, NE

(1690) (0) (50)

705 0 85 1500 (2240) 35 (65)

390 (415) 1805 (2315)

(2335) 3740 (815) 1725

(305) 265 (1570) 2100 85 0 430

(340) (0) (580)

A14

April 2017



Date

Figure

Not to Scale

´

F

F

F

F

LEGEND





X

X




Sarpy County, NE

(465) (1915) 535 (765)

430 2230 0 (0)

895 (885)

30 1525

(55) (1825)

(2060) (740)

2265 860

(475) 405

(0) 0 1150 1020

(70) 110 (1405) (900)

A15

April 2017



Date

Figure

E

D

CC

Not to Scale

´LEGEND





X

X




Sarpy County, NE

(1690) (0) (50)

705 0 85 1500 (2240) 35 (65)

390 (415) 1805 (2315)

(2335) 3740 (815) 1725

(305) 265 (1570) 2100 85 0 430

(340) (0) (580)

A16

April 2017



Date

Figure

Not to Scale

´

E

E

F

F

LEGEND





X

X




Sarpy County, NE

(1690) (50)

705 85 (815) 1725 35 (65)

(1570) 2100 1805 (2315)

(2335) 3740 1500 (2240)

(305) 265 390 (415) 85 430

(340) (580)

April 2017

A17



Date

Figure

Not to Scale

´LEGEND





X

X

B

CB

B




Sarpy County, NE

(1690) (50)

705 85 390 (415) 35 (65)

1500 (2240) 1805 (2315)

(2335) 3740 (1570) 2100

(305) 265 (815) 1725 85 430

(340) (580)

April 2017

A18



Date

Figure

Not to Scale

´

D

C

LEGEND





X

X




Sarpy County, NE

B

B

(465) (1915) 535 (765)

430 2230 0 (0)

895 (885)

30 1525

(55) (1825)

(2060) (740)

2265 860

(475) 405

(0) 0 1150 1020

(70) 110 (1405) (900)

A19

April 2017



Date

Figure

B

B

BC

Not to Scale

´LEGEND





X

X




Sarpy County, NE

(465) (1915)

430 2230

535 (765)

895 (885)

30 1525

(55) (1825)

(2060) (740)

2265 860

(475) 405

(70) 110

1150 1020

(1405) (900)

A20

April 2017



Date

Figure

Not to Scale

´LEGEND





X

X

B

B

B

B




Sarpy County, NE

(465) (1915) 535 (765)

430 2230 0 (0)

895 (885)

30 1525

(55) (1825)

(740) (2060)

860 2265

(475) 405

(70) 110 1150 1020

(1405) (900)

April 2017

A21



Date

Figure

B

C

Not to Scale

´LEGEND





X

X

B

B




Sarpy County, NE

(80) (1400) 450 (940)

175 1730 0 (0)

110 (160)

40 740

(30) (810)

(820) (580)

780 950

(150) 50

(0) 0 780 130

(30) 20 (840) (110)

A22

April 2017



Date

Figure

A

C

CB

Not to Scale

´LEGEND





X

X



180th/192nd New Interchange (Diamond Configuration)Traffic Volumes and Operations Analysis Results

Sarpy County, NE

180th

Str

eet

192n

d S

treet

(80) (1400)

175 1730

450 (940)

110 (160)

40 740

(30) (810)

(820) (580)

780 950

(150) 50

(30) 20

780 130

(840) (110)

A23

April 2017



Date

Figure

Not to Scale

´LEGEND





X

X

B

B

B

B

180th

Str

eet



180th/192nd New Interchange (DDI Configuration)Traffic Volumes and Operations Analysis Results

Sarpy County, NE

192n

d S

treet

(80) (1400) 450 (940)

175 1730 0 (0)

110 (160)

40 740

(30) (810)

(580) (820)

950 780

(150) 50 780 130

(0) 0 (840) (110)

(30) 20

April 2017

A24



Date

Figure

A

C

Not to Scale

´LEGEND





X

X

A

A



180th/192nd New Interchange (Parclo Configuration)Traffic Volumes and Operations Analysis Results

Sarpy County, NE

180th

Str

eet

192n

d S

treet

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