HomeMy WebLinkAboutA026 - Duff Avenue (Railroad to 16th Street) Corridor StudyITEM #:26
DATE:10-27-26
DEPT:PW
SUBJECT:DUFF AVENUE CORRIDOR STUDY FINDINGS
COUNCIL ACTION FORM
BACKGROUND:
Duff Avenue is a key north-south route through central Ames, linking Downtown, the Old Town
neighborhood, and the Mary Greeley Medical Center campus. It carries a mix of commuters,
patients, emergency vehicles, transit, and freight.
In July 2025, the City began a study of Duff Avenue from the Union Pacific Railroad (UPRR)
crossing near Main Street to 16th Street. The study evaluated traffic operations, safety,
walking and biking connectivity, and railroad crossing impacts and developed a long-term
improvement concept for the corridor.
The study's recommendations build on direction City Council has already set in several
adopted plans: the Ames Connect 2050 Metropolitan Transportation Plan (MTP), the Ames
Area Metropolitan Planning Organization (AAMPO) Comprehensive Safety Action Plan (which
places this part of Duff Avenue on the region's High-Priority Safety Network), Walk Bike Roll
Ames (which ranks the corridor as the top priority for a shared-use path and the East 12th
Street crossing as a top-priority crossing), the Complete Streets Plan, and the Climate Action
Plan.
JULY CITY COUNCIL WORKSHOP:
At the July 21, 2026, City Council workshop, staff presented a study update that:
Reviewed the study's background, objectives, and scope.
Summarized both rounds of public and stakeholder outreach.
Presented the traffic engineering analysis.
Showed initial improvement concepts, including a three-lane section along most of the
corridor.
Summarized railroad crossing data along Duff Avenue.
The July workshop staff report, including the presentation slides and a detailed
technical memo, is attached.
Council's feedback at the workshop helped guide the final study report. Council asked for:
1. Safety Analysis: A more specific estimate of the crash reduction Duff Avenue could
expect from a three-lane conversion, rather than simply using the national range of 19%
to 47% presented at the workshop.
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2. Travel Times: A comparison of travel times through the full corridor with the existing
four-lane section and the proposed three-lane section, instead of looking only at
intersection delay.
3. Long-Term Capacity: An estimate of how long the three-lane section would continue to
operate acceptably beyond the 2050 planning horizon.
In response, the study team completed three additional analyses after the workshop: a
Highway Safety Manual (HSM) predictive crash analysis, a microsimulation of 2050
peak-hour travel times, and a sensitivity analysis of traffic growth beyond 2050. The
results are summarized within the study findings below.
FINAL STUDY REPORT & FINDINGS:
The study report (see attached) is organized into 10 chapters and includes several
appendices.
Key findings are summarized below:
TRAFFIC CAPACITY AND TRAVEL TIMES:
Duff Avenue carries approximately 9,000 to 12,600 vehicles per day today, with
10,200 to 14,300 forecast for 2050 (based on a conservative 0.5% annual growth
rate). Even the 2050 volumes are below the 15,000 to 20,000 vehicles per day that
the Federal Highway Administration and the City's Complete Streets Plan identify
as the upper limit for converting four lanes to three.
During the PM peak hour, both today and in 2050, half of the six primary intersections
operate at level of service (LOS) A (the best rating on an A-to-F scale), and none is
worse than LOS C with the existing four-lane section. In other words, the corridor has
much more capacity than its traffic requires.
In the 2050 PM peak hour, intersection delay with the three-lane section would be
within 1.5 seconds per vehicle of the four-lane section at every signalized
intersection. Delay at 16th Street would drop significantly with either two-way stop
control or a compact roundabout.
Microsimulation (a detailed computer model of individual vehicle movements) with
2050 traffic found that the three-lane section would increase travel times by only
2.7% (4.9 seconds) in the northbound direction and 2.8% (5.2 seconds) in the
southbound direction through the entire study corridor during the PM peak hour,
compared with the existing four-lane section.
At 13th Street, the corridor's busiest intersection, traffic could keep growing at
0.5% per year for another 30 years beyond 2050 (to about 2080, roughly 30% more
traffic than today), and with a three-lane section the intersection would still
operate acceptably (overall LOS D) during peak hours.
SAFETY:
From 2021 through 2025, 96 crashes were reported in the corridor. The most common
were rear-end (27%), broadside (21%), sideswipe (16%), and left-turn (16%) crashes,
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types often associated with four-lane undivided roads, where left-turning vehicles stop in
the inside through lane.
The all-way stop at 16th Street ranks 46th of 5,255 all-way stop intersections in
Iowa for potential crash reduction, meaning it has more crashes than expected.
Five of its seven crashes involved a driver failing to stop.
The Highway Safety Manual analysis predicts that a three-lane section would
reduce segment crashes by approximately 23% from 6th Street to 16th Street. The
expected crash reduction is most pronounced from 10th Street to 13th Street,
where the change from a 5-lane section to a 3-lane section is expected to reduce
segment crashes by 36.4%.
The 85th percentile speed (the speed at or below which 85% of drivers travel) is 36 mph,
above the posted 30 mph limit. The study confirmed 30 mph is the appropriate limit,
so bringing actual speeds closer to it is a key safety goal, especially for people
walking and biking. A three-lane section would also calm traffic and help moderate
speeds.
PUBLIC AND STAKEHOLDER OUTREACH:
The first survey (March 2026, 547 responses) identified safety for all users, reducing
congestion and delays, and improving walkability and bikeability as the community's top
priorities.
In the second survey (June 2026, 711 responses), about 57% of respondents did
not support the proposed improvements, most often out of concern that fewer
through lanes would increase congestion. However, the traffic analysis above
does not support that concern. 17% of respondents were neutral and 26% were
supportive of the proposed improvements.
Mary Greeley Medical Center facilities and ambulance operations staff supported
the three-lane concept and the enhanced pedestrian crossing at East 12th Street.
STUDY RECOMMENDATIONS:
The recommended concept, primarily a three-lane section, is shown in the attached
improvement concepts and in Appendix A of the study report. Key elements include:
A three-lane section (one through lane in each direction with a center two-way left-turn
lane) from just south of 6th Street to 16th Street, connecting to the existing three-lane
section north of 16th Street. Four lanes would remain south of 6th Street to
accommodate vehicles queued during train crossings.
An 8-foot shared-use path for walking and biking along the west side of the corridor.
An enhanced pedestrian crossing at East 12th Street with a median refuge island and a
pedestrian hybrid beacon (an overhead signal that stops traffic only when activated),
which would be activated by pedestrian push buttons and automatically by ambulances
entering or leaving Mary Greeley Medical Center.
A dedicated northbound right-turn lane at 13th Street.
Bus pull-outs at the CyRide timepoint stops near 11th Street.
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At 16th Street, either two-way stop control with a pedestrian crossing enhanced by a
rectangular rapid flashing beacon (RRFB) or a compact roundabout. The study found
both alternatives feasible. Staff proposes piloting two-way stop control in the near
term (see next section) and using the results to help choose between the two
options when this segment is reconstructed.
The mid-block pedestrian crossing near Bandshell Park shown at the July workshop is
not part of the primary recommended concept, but the study includes it as an option to
consider during final design.
The corridor would likely be reconstructed in phases rather than as a single project, in
four segments (the railroad to 6th Street, 6th Street to 10th Street, 10th Street to 13th
Street, and 13th Street to 16th Street), with each segment rebuilt when its pavement
condition requires it.
Table 1 compares the study's planning-level cost estimates for reconstructing each segment
with the recommended concept versus as a four-lane section like today. Because the railroad
to 6th Street segment stays mostly four lanes, its cost difference is minor.
Table 1: Planning-Level Reconstruction Cost Estimates by Segment
Segment Reconstruct as 4/5-
Lane (Existing)
Recommended 3-
Lane Concept Difference
Railroad to 6th Street $1.75 M $1.75 M $0 K
6th Street to 10th Street $3.02 M $2.88 M - $140 K
10th Street to 13th Street $2.71 M $2.70 M - $10 K
13th Street to 16th Street
(No 16th St Roundabout)$2.66 M $2.56 M - $100 K
13th Street to 16th Street
(w/16th St Roundabout)$2.66 M $3.17 M + $510 K
Total (No 16th St
Roundabout)$10.14 M $9.89 M - $250 K
Total (w/16th St
Roundabout)$10.14 M $10.49 M + $350 K
*Note: Above amounts shown are in 2026 dollars and include administration, engineering, and
construction project costs.
A detailed life-cycle cost analysis was not performed. However, the 3-lane section
would likely cost only slightly less over its life than the existing section, because the
width reduction is minor along most of the corridor.
Reconstruction is anticipated within the next 10 to 15 years. Detailed design decisions
would be made once each project is programmed in the Capital Improvements Plan
(CIP) and enters final design.
Staff is asking City Council to accept the study as a long-term vision to guide how
future projects on the corridor are programmed. Accepting the study does not commit
the City to fund or build any specific improvement in the study.
RESTRIPING DUFF AVENUE FROM 13TH STREET TO 16TH STREET:
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Although reconstruction from 6th Street to 13th Street is likely 10 to 15 years away,
staff recommends bringing two key elements of the recommended concept to Duff
Avenue between 13th Street and 16th Street in the near term: a three-lane section and
two-way stop control at 16th Street.
This mostly residential segment carries the corridor's lowest traffic volumes (about 9,400
vehicles per day today and a projected 10,700 in 2050) and connects directly to the existing
three-lane section north of 16th Street. The changes would require no curb work or major
construction, so the street would remain wider than the section recommended for eventual
reconstruction.
The near-term changes (see attached interim improvements concept) would include:
Three-lane section: Restriping to one through lane in each direction with a center two-
way left-turn lane. A second southbound through lane would be added approaching 13th
Street, and the second northbound through lane would become a right-turn-only lane at
13th Street.
16th Street intersection: Converting the all-way stop to two-way stop control (16th
Street traffic would stop; Duff Avenue traffic would not) and adding a marked pedestrian
crossing of Duff Avenue with an Rectangular Rapid Flashing Beacon.
Speed management: Installing dynamic speed feedback signs, which display drivers'
speeds, for Duff Avenue traffic near 16th Street.
These changes work together. The study notes that removing the all-way stop would
require other traffic calming on Duff Avenue, which the single through lanes and speed
feedback signs would provide. The three-lane section would also mean pedestrians at
the new RRFB crossing cross only one through lane in each direction, avoiding the
multi-lane crossing conflict, where a driver in one lane stops for a pedestrian but a
driver in the next lane does not.
These changes would also let the City test both two-way stop control and the three-
lane section with real traffic. The existing all-way stop has more crashes than expected,
mostly involving drivers who fail to stop, and two-way stop control would eliminate most of the
intersection's delay because Duff Avenue traffic would no longer have to stop.
In the second survey, 59% of respondents preferred two-way stop control. Staff would monitor
operations and crashes at the intersection and along the restriped segment to help choose
between two-way stop control and a compact roundabout when this segment is reconstructed.
The estimated cost to restripe Duff Avenue is approximately $75,000:
Slurry seal, 13th Street to 16th Street: $25,000
Pavement markings (paint and arrows): $27,000
RRFB and pedestrian signage at 16th Street: $15,000
Dynamic speed feedback signs: $8,000
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A slurry seal is a thin layer of asphalt emulsion and fine aggregate spread over existing
pavement to seal cracks and renew the surface. Applied before restriping, it would add a few
years of pavement life and give the new markings a fresh surface, avoiding the “ghosting” that
typically remains when old markings are removed and new ones are painted elsewhere.
If directed by City Council, staff would fund this work through the CIP's Pavement
Restoration Program (slurry seal and pavement markings) and Accessibility
Enhancements Program (pedestrian crossing and speed feedback signs), with
implementation likely in 2028 in coordination with the 6th Street to 13th Street
resurfacing project that is currently programmed in FY 2027/28 in the Arterial Streets
Program.
DUFF AVENUE RAILROAD CROSSING:
The corridor study assessed delays and traffic impacts from the UPRR at-grade (street-level)
crossing of Duff Avenue just south of Main Street, but it did not evaluate a grade separation
(an underpass or overpass that would carry Duff Avenue under or over the tracks so traffic no
longer has to stop for trains). The study's recommended concept, therefore, assumes the at-
grade crossing remains in place. However, the study confirmed that the crossing is the
largest source of delay on the corridor and recommends that the City consider a future
detailed study of a grade separation.
Crossing data collected for this corridor study showed:
An average of 38 trains per day, with the crossing blocked for approximately two
hours per day.
An average gate-down time of 3 minutes and 15 seconds per train.
Peak-period recovery times (the time needed for backed-up traffic to clear) of up to 90
seconds after each train, with northbound queues reaching approximately 730 feet.
The crossing also stands out state-wide. The Federal Railroad Administration (FRA) crossing
inventory lists about 43 through trains, 8 switching movements, and 13,100 vehicles per day at
the crossing, giving Duff Avenue the highest exposure (trains multiplied by vehicles) of
any at-grade crossing in Iowa, nearly 50% higher than the next-highest crossing. FRA
records show 21 collisions at the crossing since 1978, resulting in eight fatalities (five of them
pedestrians) and five injuries. Four of those collisions have occurred since 2000, including a
pedestrian fatality in 2010 and a pedestrian injury in 2018.
The crossing was also a consistent theme in public and stakeholder input. In the first survey,
train delays were the second most common traffic frustration (54%), and 92% of respondents
said train backups were at least a minor issue for them. In the second survey, 75% of
respondents supported a detailed study of the crossing. Mary Greeley Medical Center
ambulance operations staff also asked the City to explore a grade separation because
trains affect ambulance routing and response times. The study notes that long train
crossings, derailments, and track maintenance will continue to disrupt the corridor regardless
of lane layout.
The Ames Connect 2050 Metropolitan Transportation Plan scores the grade separation as
the highest-ranking priority project in the MPO's planning area. The Plan indicates that a
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study of the railroad crossing is a near-term priority (to be undertaken sometime in the
next five years).
2003 Duff Avenue Crossing Study
The City last studied this crossing in 2003 (report attached). At that time, the crossing carried
more than 16,000 vehicles and about 60 trains per day, already had the highest exposure of
any crossing in Iowa, and had been the site of eight fatalities over the previous 25 years. The
study also assumed Duff Avenue needed to be four or five lanes wide. After evaluating more
than 15 alternatives, the consultant and City staff recommended seeking federal funding for a
Duff Avenue underpass (estimated at $16.5 million at the time).
The underpass had the highest benefit/cost ratio of the finalists but would have
required seven business relocations. The study's Issues Committee of business,
neighborhood, and resident representatives instead favored a no-build option, citing
impacts on Downtown businesses, cost, and a desire to wait for the Grand Avenue
extension and Dayton Avenue overpass. On February 25, 2003, City Council voted
unanimously to finalize the report based on the no-build option.
ALTERNATIVES:
Motion A – Corridor Study Findings
1A.Accept the Duff Avenue (Railroad to 16th Street) Corridor Study.
2A.Accept the Duff Avenue (Railroad to 16th Street) Corridor Study with modifications
identified by City Council.
3A.Do not accept the study.
Motion B – Restriping Duff Avenue from 13th Street to 16th Street
1B.Direct staff to restripe Duff Avenue from 13th Street to 16th Street from four lanes
to three, and to convert the Duff Avenue and 16th Street intersection to two-way
stop control with an RRFB-enhanced pedestrian crossing.
2B.Keep the existing four-lane section and all-way stop at 16th Street until the corridor
is reconstructed in 10 to 15 years.
CITY MANAGER'S RECOMMENDED ACTION:
The study found that Duff Avenue has far more vehicle capacity than it needs, both today and
through 2050, along with documented safety and pedestrian crossing problems. The
recommended three -lane concept addresses those problems with little change in
corridor travel times or intersection delay compared with the existing four-lane section.
The recommended change is expected to reduce segment crashes from 6th Street to
16th Street by approximately 23%, and it advances priorities City Council has already
adopted in previous plans. Accepting the study would establish this concept as the long-
term vision for the corridor and guide future reconstruction projects over the next 10 to
15 years.
Restriping Duff Avenue from 13th Street to 16th Street and converting the 16th Street
intersection to two-way stop control would bring key elements of the recommended concept to
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this segment in the near term, for approximately $75,000 and within the existing roadway
w idth. It would address the 16th Street all-way stop, which ranks 46th of 5,255 all-way
stop intersections in Iowa for potential crash reduction, while greatly reducing delay
there. It would also let staff evaluate how the two-way stop control layout operates at
the 16th Street intersection, which would help inform the future choice between two-
way stop control and a compact roundabout.
Therefore, it is the recommendation of the City Manager that the City Council adopt
Alternatives 1A and 1B, as described above.
ATTACHMENT(S):
Duff Ave Corridor Study - Final Report.pdf
Duff Ave Corridor Study - Recommended Improvement Concepts.pdf
Duff Ave Corridor Study - Interim 13th to 16th Restripe Concept.pdf
Staff Report (07.21.26 City Council Workshop).pdf
Final Report (2003 Duff Ave UPRR Study).pdf
Duff Ave Corridor Study - Presentation Slides.pdf
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