HomeMy WebLinkAbout1stAve_4-3lane_TrafAnalysis.pdfFirst Avenue
Lane Reconfiguration
Iowa City, Iowa
Prepared By:
Prepared For:
City of Iowa City
July 6, 2016
First Avenue
Lane Reconfiguration
Prepared by:
Snyder & Associates, Inc.
Prepared for:
City of Iowa City
July 6, 2016
I hereby certify that this Engineering Document was prepared by me or
under my direct personal supervision and that I am a duly Licensed
Professional Engineer under the Laws of the State of Iowa.
Justin C. Jackson, P.E. Date
License Number 20538
My License Renewal Date is December 31, 2016
First Avenue 4 Lane to 3 Lane Conversion Study Page 1
Snyder & Associates, Inc.
Background
Iowa City submitted and was successful in applying for the Iowa DOT Traffic Safety Improvement
Program (TSIP) funding in 2014 for First Avenue 3-lane conversion from US 6 to north of Mall
Drive. The following report summarizes the findings of a detailed capacity analysis of converting
First Avenue from a 4-lane to a 3-lane roadway (with continuous center left turn lane) based on
current and future forecasted traffic conditions. Iowa City’s DOT Traffic Safety Funds application
was used for existing conditions, historic traffic data, and project concept for the corridor.
Traffic History
Iowa Department of Transportation (DOT) historic counts were compiled from similar locations
within the corridor to estimate a traffic growth rate and identify traffic pattern trends. The annual
average daily traffic (AADT) volumes from the DOT counts for years 2002, 2006, 2010, and 2014
are shown in Table 1 for locations within the corridor. As is illustrated in Table 1, most of the
segments experienced steady traffic volumes or traffic volume decline. The City collected peak
hour counts at intersections in the corridor as part of the TSIP application. The total peak hour
traffic volumes on First Avenue at intersection approaches are listed in Table 2. Since peak hour
counts at Mall Drive and Lower Muscatine Road were conducted a week apart in 2013, the actual
peak hour traffic volume counted was used for analysis although the exiting volumes from one
intersection do not equal the entering volume at the next intersection. However, since the peak hour
count at the intersection of US Hwy 6 was conducted in 2009 and there are no accesses between this
intersection and Lower Muscatine Road intersection, the peak hour volume at US Hwy 6 was
adjusted so that the exiting volumes from one intersection equaled the entering volume from the
other intersection. The percentage change of the adjusted turning traffic volume at US Hwy 6 was
also applied to the through traffic volumes at the intersection.
Table 1: Historic Annual Average Daily Traffic
Roadway Segment
(First Avenue)
Historic Daily Traffic
2002 2006 2010 2014
Mall Drive, south of 12,800 - 13,000 -
US Hwy 6, north of 11,100 10,900 11,000 9,500
- DOT did not count location during count year
Table 2: Existing Total Peak Hour Traffic Volumes
Roadway Segment
(First Avenue) AM PM
Mall Drive, north of 1,216 1,725
Mall Drive, south of 944 1,343
Lower Muscatine, north of 930 1,202
US Hwy 6, north of 685 931
Traffic Volume Forecasts
Metropolitan Planning Organization of Johnson County (MPOJC) provided traffic volumes from
their regional travel demand model for base year 2010 and the 2040 horizon year as the source of
information for annual rates of traffic change for the corridor. The traffic demand model addresses
First Avenue 4 Lane to 3 Lane Conversion Study Page 2
Snyder & Associates, Inc.
future changes in the region and/or corridor development trends that are different from the historical
trend. In addition, the model has the capability of taking into account street network changes that
may result in First Avenue becoming a more attractive or less attractive route relative to alternative
corridors. Thus, there is the potential for observing substantial changes from historical traffic
trends if there are forecasted employment, residential development, or roadway network changes
from the current conditions or historical trends.
MPOJC base year traffic volumes, future year traffic volumes, and annual change rate are listed in
Table 3. Table 4 lists the future year 2040 total peak hour traffic volumes. The annual rate of
traffic volume change was applied to existing peak hour traffic volumes to calculate future 2040
peak hour traffic volumes. At the intersection of Mall Drive, only the through traffic volumes on
First Avenue had a growth factor applied in the analysis of future conditions since one approach of
the intersection is a business access and Mall Drive only connects to fully developed parcels. The
growth rate applied to turning traffic from Lower Muscatine Road corresponded to the growth rate
of the segment the vehicles were turning on to. The through traffic volumes on Lower Muscatine
Road had a growth rate of 0.32% applied for future analysis.
Table 3: MPOJC Traffic Model Volumes
Roadway Segment
(First Avenue)
Daily Traffic
2010 2040 Annual Rate
Mall Dr to Lower Muscatine Rd 13,000 14,300 0.32%
Lower Muscatine Rd to US Hwy 6 11,000 12,800 0.51%
Table 4: 2040 Total Peak Hour Traffic Volumes
Roadway Segment
(First Avenue) AM PM
Mall Drive, north of 1,312 1,830
Mall Drive, south of 1,018 1,448
Lower Muscatine, north of 1,034 1,336
US Hwy 6, north of 773 1,052
Proposed Corridor Improvements
The current and forecasted traffic volumes for the corridor are within the limits of what a 3-lane
roadway can typically accommodate with acceptable user delay. The 3-lane corridor was evaluated
with every signalized intersection providing protected/permissive left turn phasing on First Avenue
along with the traffic signals operating in coordination. The existing and future 3-lane traffic
conditions were analyzed with the following improvements:
x 3-lane cross section from Mall Drive (connecting to the proposed 3-lane cross section from
the railroad grade separation project) to US 6
o 1 NB Shared through/right turn-lane
o 1 Southbound through/right turn-lane
o 1 Continuous center left turn-lane
o Designated bike lanes from Mall Drive to Lower Muscatine Road
x Protected/permissive left turn phasing at all signalized intersections
x Traffic signals operating in coordination
First Avenue 4 Lane to 3 Lane Conversion Study Page 3
Snyder & Associates, Inc.
x Dedicated left turn lanes at signalized intersection with 100’ of storage
Capacity and Intersection Analysis
Traffic operations were evaluated at each key intersection using the existing conditions, existing
traffic volumes with 3-lane configuration, and year 2040 forecasted traffic volumes with 3-lane
configuration for AM and PM peak period traffic volumes. The measures of effectiveness (MOE’s)
for the corridor were characterized by quantifying the following:
x The level-of-service (LOS) at each intersection for either STOP controlled or traffic
signalized intersection resulted from applying Highway Capacity Manual, 2010 (HCM)
methodology incorporated into traffic analysis and modeling software, Synchro 8.
x Corridor travel time and delays of the corridor were modeled utilizing SimTraffic 8 traffic
signal coordination software.
At signalized intersections, the LOS is based on the weighted average of all approach delays and is
expressed as a letter grade from A through F, with each grade representing a range of vehicle delay.
Analysis of 3-lane configurations includes the proposed improvements previously described. Tables
5 and 6 list HCM computed vehicle delay and LOS of each intersection by approach for existing
conditions, existing traffic volume with 3-lane configuration, and forecasted traffic volumes with 3-
lane configurations for AM and PM peak periods. The current delay and LOS per each intersection
approach and movement is acceptable (LOS D or better). Reconfiguring First Avenue to a 3-lane
cross section will increase the intersection vehicle delay by 10 to 20 seconds and decrease the LOS
during the peak periods. However the LOS will still stay acceptable with the lane reconfiguration
with current traffic volumes and forecasted traffic volumes. The directional travel times along the
corridor during the peak analysis periods are listed in Table 7.
Table 7: Travel Time in Seconds
Peak
Hour
Direction of
Travel
2016
Model
4-lane
2016
Model
3-Lane
2040
Model
4-Lane
2040
Model
3-Lane
AM
Peak
Northbound 56 57 58 58
Southbound 99 104 111 110
PM
Peak
Northbound 68 68 65 65
Southbound 109 117 112 125
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Page 4 Snyder & Associates, Inc.
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2
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3-
L
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Pe
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Vo
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4-
L
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3-Lane
De
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(s
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)
LO
S
Ma
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Qu
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e
(f
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/
l
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De
l
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(s
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ve
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LO
S
Ma
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Qu
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(f
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De
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(s
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/
ve
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)
LO
S
Ma
x
Qu
e
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e
(f
t
/
l
a
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e
)
Delay (secs/ veh) LOS Max Queue (ft/lane)
Ma
l
l
D
r
NB
5
1
9
4
A
1
3
0
6
A
1
8
0
/
T
h
5
2
2
4
A
1
6
0
6
A
1
9
0
/
T
h
SB
6
1
3
4
A
1
1
0
8
A
3
0
0
/
T
h
6
9
5
4
A
1
9
0
9
A
3
0
0
/
T
h
EB
1
1
3
1
4
B
6
0
4
1
D
1
3
0
1
1
4
1
5
B
6
0
4
1
D
1
5
0
WB
3
1
2
B
3
0
3
6
D
3
0
3
1
3
B
3
0
3
6
D
3
0
Al
l
12
4
8
5
A
11
B
13
3
4
5
A
11 B
Lo
w
e
r
Mu
s
c
a
t
i
n
e
Rd
NB
3
7
6
1
2
B
1
8
0
1
8
B
1
6
0
/
T
h
4
5
2
1
3
B
2
0
0
2
1
C
3
1
0
/
T
h
SB
4
1
3
1
2
B
1
4
0
1
9
B
2
6
0
/
T
h
4
1
6
1
3
B
2
0
0
2
1
C
2
5
0
/
T
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EB
1
9
7
1
2
B
1
6
0
/
L
t
2
7
C
1
6
0
/
L
t
2
2
2
1
3
B
1
4
0
/
T
h
2
7
C
1
4
0
/
T
h
WB
2
4
1
1
8
B
1
6
0
/
T
h
4
6
D
2
8
0
/
T
h
2
6
8
2
0
B
2
0
0
/
T
h
3
9
D
2
9
0
/
T
h
Al
l
12
2
7
13
B
26
C
13
5
8
14
B
26 C
US
H
w
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6
SB
3
1
1
2
2
C
1
3
0
/
R
t
5
2
D
7
0
/
L
t
3
2
3
2
3
C
1
3
0
/
L
t
4
0
D
9
0
/
L
t
EB
7
1
6
1
0
A
2
5
0
/
L
t
2
5
C
3
6
0
/
L
t
7
6
7
1
1
B
3
5
0
/
L
t
2
4
C
3
5
0
/
L
t
WB
4
3
3
1
3
B
1
4
0
/
T
h
3
9
D
2
5
0
/
T
h
4
2
2
1
5
B
1
6
0
/
T
h
4
2
D
1
8
0
/
T
h
Al
l
14
6
0
12
B
30
C
15
1
2
13
B
31 C
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Page 5 Snyder & Associates, Inc.
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Delay (secs/ veh) LOS Max Queue (ft/lane)
Ma
l
l
D
r
NB
6
0
9
6
A
1
1
0
9
A
2
9
0
/
T
h
6
7
5
6
A
1
4
0
1
0
B
2
1
0
/
T
h
SB
8
2
8
6
A
2
8
0
1
9
B
6
2
0
/
T
h
9
4
1
7
A
2
4
0
1
9
B
6
2
0
/
T
h
EB
2
2
9
1
8
B
1
9
0
3
4
C
1
5
0
2
3
0
3
7
D
2
3
0
4
2
D
3
4
0
WB
6
1
4
B
3
0
2
3
C
3
0
6
2
9
C
3
0
6
9
E
3
0
Al
l
16
7
2
8
A
17
B
18
5
2
11
B
19 B
Lo
w
e
r
Mu
s
c
a
t
i
n
e
Rd
NB
4
0
2
1
1
B
1
6
0
1
6
B
1
2
0
/
T
h
4
4
5
1
2
B
2
0
0
1
9
B
1
4
0
/
T
h
SB
6
5
9
1
3
B
3
2
0
2
0
B
3
6
0
/
T
h
6
8
0
1
3
B
4
4
0
2
7
C
6
3
0
/
T
h
EB
3
4
3
1
5
B
1
6
0
/
L
t
3
3
C
1
6
0
/
T
h
3
7
0
2
8
C
1
9
0
/
T
h
2
9
C
3
7
0
/
T
h
WB
2
8
3
1
9
B
2
0
0
/
T
h
3
7
D
2
3
0
/
T
h
3
0
4
3
9
D
1
8
0
/
T
h
3
6
D
3
3
0
/
T
h
Al
l
16
8
7
14
B
24
C
17
9
9
20
C
27 C
US
H
w
y
6
SB
5
7
1
2
0
B
1
5
0
/
R
t
3
4
C
1
3
0
/
R
t
6
0
8
3
7
D
2
2
0
/
R
t
3
6
D
1
7
0
/
R
t
EB
1
0
3
5
9
A
3
1
0
/
L
t
2
1
C
2
9
0
/
L
t
9
9
1
2
4
C
3
2
0
/
L
t
2
0
C
3
3
0
/
L
t
WB
4
6
0
1
3
B
1
2
0
/
T
h
3
7
D
1
7
0
/
T
h
4
0
2
3
7
D
1
6
0
/
T
h
4
0
D
2
1
0
/
T
h
Al
l
20
6
6
10
B
26
C
20
0
1
29
C
26 C
First Avenue 4 Lane to 3 Lane Conversion Study Page 6
Snyder & Associates, Inc.
Summary
Given the existing traffic volumes and the number of accesses on First Avenue from Lower
Muscatine Road to Mall Drive, converting the 4-lane roadway to a 3-lane roadway with a
continuous center left turn will increase intersection vehicle delay by 10 to 20 seconds during the
peak periods. However the vehicle delay and LOS will remain acceptable while providing a
beneficial left turn lane for vehicles utilizing the accesses between intersections. Reconfiguring
First Avenue from 4-lane to 3-lane cross section will increase the projected travel time by 10
seconds in the PM peak period upon implementation of the lane reconfiguration. This portion of
Iowa City is developed therefore future forecasted traffic volumes along the corridor are projected
to have a minimal increase since there are no undeveloped areas adjacent to the corridor.
The existing business accesses along First Avenue do not all align opposite from one another except
the north access of Eastdale Plaza on the east side of First Avenue and Java House on the west side
of First Avenue. An unaligned access can cause the potential of left turning vehicle conflicts if they
are not directly across from one another, or offset downstream from one another (for example, if an
access to the east is south of an access to the west, the left turning vehicle paths may overlap). A left
turn conflict was identified as a left turning vehicle having the potential to block the continuous left
turn lane for an opposite direction of travel left turning vehicle. However, since all the accesses are
offset upstream from one another, a left turn conflict does not exist except for one location. One
location that does have the potential of left turning vehicle conflict is the southern access of
Eastdale Plaza on the east side of First Avenue and Java House on the west side of First Avenue.
To eliminate left turning vehicle conflict, either the southern access to Eastdale Plaza should be
eliminated or access to Java House should be eliminated. Additional analysis of internal site
circulation should be conducted to determine the feasibility of closing either of the two accesses. If
the sites were to be redeveloped, the number and locations of the accesses should be reviewed as it
relates to corridor access management and adjacent property accesses.
The future 3-lane traffic conditions should mimic existing 3-lane traffic conditions as tabulated with
acceptable vehicle delay with the following recommended improvements to the corridor:
x 3-lane cross section from Mall Drive (connecting to the proposed 3-lane cross section from
the railroad grade separation project) to US 6
o 1 NB Shared through/right turn-lane
o 1 Southbound through/right turn-lane
o 1 Continuous center left turn-lane
o Designated bike lanes from Mall Drive to Lower Muscatine Road
x Protected/permissive left turn phasing at all signalized intersections
x Traffic signals operating in coordination
x Dedicated left turn lanes at signalized intersection with 100’ of storage