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Preliminary 1999 Iowa Bypass Study. Prepared by Snyder & Associates, Inc. for the Iowa Dept. of Transportation and presented to the Bloomfield City Council & Community Wednesday, September 29, 1999. Why Iowa Builds Bypasses.

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preliminary 1999 iowa bypass study

Preliminary1999 Iowa Bypass Study

Prepared bySnyder & Associates, Inc.

for the

Iowa Dept. of Transportation

and presented to the

Bloomfield City Council & Community

Wednesday, September 29, 1999

why iowa builds bypasses
Why Iowa Builds Bypasses
  • Part of the Commercial Industrial Network (CIN) investment strategy.
    • Improve flow of commerce: longer trips, improve travel time.
    • Make travel more convenient, safe & efficient: limited access highways, no slow down in small towns, eliminate competition with local traffic/pedestrians.
    • Better connect Iowa with regional, national & international markets.
    • Concentrate a major portion of annual construction budget on CIN.
interstate cin arterials of the state
Interstate & CIN:Arterials of the State
  • 64% of rural highway traffic is on the Interstates & CIN system.
  • 82% of rural semi-truck traffic is on Interstates or CIN (20% uses CIN).
  • 80%+ of Iowans live within 10 miles of the Interstate or CIN.
  • Interstate & the CIN account for only 32% of the total rural highway miles.
12 study communities
12 Study Communities

Bypass Community Pop. Bypass Route Year Bypass Opened

  • Denver 1600 US Hwy 63 1994
  • Eldridge 3638 US Hwy 61 1983
  • Independence 5972 US Hwy 20 1983
  • Maquoketa 6130 US Hwy 61 1998
  • Ogden 1909 US Hwy 30 1968
  • Pella 9270 IA Hwy 163 1994
  • Perry 7244 IA Hwy 141 1977
  • Prairie City 1366 IA Hwy 163 1997
  • Waverly 8539 US Hwy 218 1997
  • Winterset 4196 US Hwy 169 1977
  • Cascade 1812 US 151 Future
  • Iowa Falls 5435 US Hwy 20 Future


  • Bloomfield 2580 US Hwy 63 Future
study scope
Study Scope
  • Summarize other research.
  • Collect & analyze basic socio-economic data for 12 communities.
  • Make site visits and interview local leaders, officials, and business people.
  • Write up individual case study findings for each community.
  • Summarize findings of new research.
what we looked at
What we looked at:
  • Retail Sales Analysis
  • Regular City Valuation
  • Changes in Traffic Patterns & Volumes
  • Population
  • Misc. Factors
    • Regional Population & Distance from Metro.
    • Local Major Employers - what types
what we didn t do
What we didn’t do:
  • Develop predictive models of bypass impacts.
  • Conduct travel time/destination surveys.
  • Conduct statistical analysis to separate bypass impacts from other local impacts (i.e. job loss/gain, nearby attractions, regional/national economic conditions, etc.)
previous case study research
Previous Case Study Research
  • Impacts of Highway Bypasses on Kansas Towns, 1996.
  • The Economic Impacts of Highway Bypasses on [Wisconsin] Communities, 1998.
  • Economic Impacts of [Texas] Highway Bypasses, 1992.
  • The Economic Impact of Rural Highway Bypasses: Iowa and Minnesota Case Studies, 1992.
  • A Literature Review of Urban Bypass Studies, Iowa DOT, 1992.
conclusions of previous research
Long term, no significant negative impact; some benefit from encouraging location of basic industries (results in spin off $ in other sectors).

Short term, only negative impacts in some travel related/dependant businesses.

Towns over 2,000 pop. and county seat most likely to see community-wide benefit.

Commercial property values on “old route” do not decrease.

In larger, established towns, traffic on the “old route” is close to pre-bypass volumes.

Percentage of “impulse” or drive-by customers is declining - not as big as in 1970s.

More impact than Bypass:


Fuel efficient cars

Changing travel habits/ commuting

4-lane highways

Urbanization of the Midwest

Conclusions of Previous Research
conclusions of previous research1
Merchants thought bypass improved “quality of life” & shopping environment.

Safety, noise, etc. improved in downtown and residentail areas after the bypass.

Merchants observed traffic reductions but reported little (or no) loss of business activity.

Growth tends to spread along “connector” roads to bypass interchanges.

Distance of the downtown from the bypass has no long term impact.

Travel related businesses that close after bypass are usually replaced.

Communities realized that a highway improvement and bypass will require preparation & planning.

Conclusions of Previous Research
changes in population
Changes in Population
  • Studied population changes of 127 Iowa communities.
  • Divided communities into communities with a bypass, communities on the CIN, and county seat communities.
  • Study shows no indication of bypass causing a decrease in population or overall economic activity.
  • Towns on the CIN experiencing growth since the 1950s with and without a bypass.
  • Other factors, such as access to markets (via highway, rail, air, or water), have more impact on population than presence of a bypass alone.
historical retail sales for study communities 1971 97
Historical Retail Sales for Study Communities: 1971-97
  • Indexed per capita retail sales for the town against the state (i.e. ISU Extension’s “Pull Factor”).
  • The Study towns follow typical pattern, gradual decline through 1970-80s, followed by stabilization from ~1987.
  • A Control group of Non-CIN/Non-Bypass towns* more “remote” in 1970s but suffered more drastic decline overall. Same as CIN/Bypass towns by late 1990s. This highlights change in travel and purchasing patterns.
  • Many forces at work, bypass is small part. Urbanization, Ag economy, changing travel patterns bigger factors.

* Centerville, Grundy Center, Oelwein, Shenandoah, Vinton, Washington, West Liberty.

changes in downtown old route traffic volumes
Changes in Downtown “Old Route” Traffic Volumes


Sample communities under

2,000 population, limited CBD

  • Denver 7,800 2,760 - 65%
  • Prairie City 6,000 2,609 - 57%

Sample communities over

5,000 population, CBD, destination

  • Pella 11,100 11,400 + 3%
  • Waverly 9,700 10,100 + 4%
what do the traffic changes mean
What do the traffic changes mean?
  • Removes trucks, improves safety, reduces noise.
  • In small communities, most highway traffic is “through trips.”
  • In larger communities traffic in the downtown CBD may even increase after the bypass.
    • Established destination: shopping, county seat, jobs, service business, tourism, etc.
    • Local traffic starts to use “Main St.” again relieving surrounding residential arterials. Improves safety in surrounding neighborhood.
change in regular city valuation
Change in Regular City Valuation
  • Wide variation in growth rate among bypass communities, but average growth rate is same as the state average for all cities.
  • In general, cities nearer metropolitan/micropolitan areas had higher growth rate. (i.e. Denver, Eldridge, Independence)
  • Some link to opening of bypass or 4-lane highway (i.e. Prairie City)
indexed change in regular city valuation
Indexed Change in Regular City Valuation

Indexed on FY 1989 = 1.0

Future Bypass

1990s Bypass

1980s Bypass

1960-70s Bypass


Study Avg.

Avg. all Iowa cities

study conclusions
Every community thought that the bypass had been beneficial, especially for removing trucks/through traffic, & improving safety and the quality of life.

Those towns that benefited most planned for changes or took advantage of new situations & opportunities.

Working with DOT can help to achieve best results/orientation of the bypass to benefit town.

Population was unaffected.

In larger communities, traffic on “old route” is increasing (& generally higher volumes than on the bypass). Retail sales and city valuations are generally not negatively impacted.

Safety, noise, etc. is improved in neighboring streets.

Bypasses play a small role in overall economic vitality: regional & ag. economy, commuting, urbanization, access to regional highways, etc. all more important.

Study Conclusions