Statewide Modeling and Corridor Management

CE 451/551

A good reference: http://onlinepubs.trb.org/onlinepubs/circulars/ec011/ec011.pdf

Presentation Outline Statewide Models Managing Access in

Commuting Corridors

What is a Statewide Model?

Very similar to a Metropolitan Area Travel Demand Model. Wider in scope!

Many use the same sequential 4-Step Process Trip Generation Mode Split Trip Distribution Traffic Assignment

Truck Model Freight Model Intercity Bus Air and Barge

Why Model Statewide? We are seeing the benefits modeling brings

to urban areas. Technical basis behind big $ projects. In the rural area there is no such technical

tool to support decision making. Currently use old fashioned hand-drawn

methods to forecast traffic.

Why Model Statewide? Traffic forecasts affect every aspect of a State

DOT’s core business activities. Planning, finance, programming, design, construction

and maintenance. A useful, cost-effective tool

System, corridor, project level analysis for evaluating needs and alternatives

Consistent methodology Better than current DOT method. Two forecasters-two

forecasts.

Why Model Statewide? Policy questions State Gas Tax Increase Project Prioritization Statewide VMT by geographic area to determine

where dollars should be spent State Plan (like MPO Plan) Bypass Studies Corridor Studies Rural detour studies

Why Model Statewide? One major construction project costs

millions of dollars. Shouldn’t it be based on the best available data?

Project Example US 218 – Charles City, Iowa Area. Avenue of the Saints.

St. Louis, Missouri and St. Paul, Minnesota Systems Planning did a traffic forecast for

pavement design. Old fashioned trend line growth analysis. We totally missed on the Truck percentages. Route experienced significant increases in truck

volumes.

Maps from www.iowadotmaps.com

Project Example What happened?

Asphalt pavement mix substandard for those truck weights.

Result: Significant rutting. Too many dynamics taking place.

Statewide Model likely benefit. Could have saved a lot of $.

Truck trends

0%

10%

20%

30%

40%

50%

60%

70%

Urban- IS Urban-NHS

Rural- IS Rural -NHS

1998

2020

Percentage of Segments with Over 10,000 Trucks, Comparison of 1998 to 2020.Percentage of Segments with Over 10,000 Trucks, Comparison of 1998 to 2020.

National Trend

Opportunity for Modelers Large Scale Plans require Huge Investments Need Computer Models to Help Decisions Statewide Model new in Iowa - MI had one in

the 1960s see: http://onlinepubs.trb.org/onlinepubs/circulars/EC011/NELLET.PDF

Built from Urban Knowledge Base Severely Lacking Intercity Data Lacking in Data Overall

Survey Data

Data Collection is Key Data or Theory? Shortcomings in Both Behavioral Surveys are needed Origin Destination Surveys are needed Focused to Specific Corridors Economic Interaction Surveys Commodity Flow Surveys

Other States Louisiana Maine Virginia Texas Michigan Ohio Wisconsin Florida California

New Hampshire North Carolina South Carolina Oregon Mississippi Vermont Missouri Kentucky Now Iowa

Statewide Modeling Capabilities Passenger Car Models Truck Models Freight Models Rail Models Intercity Bus Air Barge Intermodal Connections Time of Day Trip Purpose

Ohio Example

Nationwide Coverage

Coded Area Type

Virginia Example

County Level Zones

Virginia Example

County Level Zones to Larger Areas

Virginia Example Network

Why is this road needed?

Kentucky Zone Example

Kentucky Zone Example

Iowa’s Model will simulate this structure.

BEABusiness Economic Areas

Trip Generation Data Population Employment CTPP National Survey Data Reebie Data (now Global Insight):

Transsearch database

Trip Purposes Home Based Work Home Based Non-Work Urban Non-Home Based (2,500 +) Rural Non-Home Based Tourist Truck and External Trips

Special Generators Intermodal Centers Tourist Attractions Etc.

Trip Distribution Even though there are issues the Gravity

Model is the common choice Issue – Rural vs Urban Trip Lengths

Trip Distances are Different Why we have both urban and rural trip

purposes

Trip Assignment All or Nothing Capacity Restraint – Traditional Pre-Assignment of Trucks

Ensures trucks stay on through routes Don’t use Equilibrium Assignment

Calibration vs Validation No Widely Accepted Standards Lenient FHWA standards apply. +/- 4,000 ADT

Typical Cost and Time Depends on Multimodal Detail Depends on Data Available Are Travel Surveys Needed? Range to Expect $300,000 - $2 million Or $6 million for Activity Based like Ohio Typically, a multi-year effort

Process to Identify High Priority Corridors for Access Management Near Large Urban Areas in Iowa

David Plazak and Reg SouleyretteCenter for Transportation Research and Education

Iowa State University

Iowa DOT Access Priority Ratings (English Conversion)

Source: Iowa DOT.

Rating Description

1 Access points at interchanges only

2 Access points spaced at minimum 2625 ft

3 Access points spaced at minimum 984 ft rural, 656 ft urban

4 Access points spaced at minimum 656 ft rural, 328 ft urban

5 Iowa DOT has minimum access rights acquired

6 Iowa DOT has no access rights acquired

Research Project Goals

Address current and future access management problems on state highway routes located just outside urban areas that serve as major routes for commuting

There were two basic goals for the project: Develop a ranking system for identifying high-priority segments

for access management treatments on primary highways outside metro and urban areas.

Focus efforts on routes that are major commuting routes at present and in the future

An example commuting corridor: US 6 to the west of the Des Moines metropolitan area (on next slide)

US 6, In The Waukee Area

Technologies Used Arc View GIS was used to integrate various

Iowa DOT databases, including roadway characteristics, traffic, and crash records

A 2940 zone traffic model was developed to estimate and forecast commuting activity on all Primary routes 

Known model weakness: border metro areas  

Iowa Forecast Population Growth By County

Source: Woods and Poole Economics

Traffic Model Zone Structure

Traffic Analysis Zones (TAZs) were developed from US Census Block Groups.

ArcView was used to find the center of each TAZ and then create a centroid at this location

The centroids were then connected to the network at breaks in the existing network

To reduce the number of segments and nodes between intersections, ArcInfo was used to combine multiple segments into a single link

ArcView was then used to create node and link files formatted for use in TRANPLAN

Base-year Estimated Traffic Model Commuting Trip Volume

5-Year Estimated Traffic Model Commuting Trip Volume

Forecast Absolute Change In Commuting, 1999-2004

Forecast Percentage Change In Commuting, 1999-2004

Access-Related Crashes Included In The Analysis

Collision Type Description

4 Rear-end/right-turn collision

5 Rear-end/left-turn collision

12 Broadside/right-angle collision

13 Broadside/right-entering collision

14 Broadside/left-entering collision

Ranking Factors Used Frequency Rate Loss/Severity Percentage

Access Related

Access-Related Crash Losses on Commuter Routes by Iowa DOT District

District

Crash Loss

Access Crash Loss

Access Related Ratio

District to State Ratio

1$19.3B

$4.1B21.45% 54.52%

5$9.1B $1.7B

18.51% 22.41%

6$5.8B $830M

14.23% 10.93%

2$1.8B

$490M26.26% 6.43%

4$1.3B $350M

25.66% 4.65%

3$750M $80M

10.63% 1.05%

Total$38.2B $7.0B

20.00% 100.00%

Red circles indicate pilot projects

“Pro-Active Corridors” Some corridors may not have access-

related crash problems today, but could have in the future

“Pro-Active Corridors” were identified based on the following factors: Forecast commuting traffic growth Proximity to metro and large urban areas Access priority ranking of 3, 4, 5, 6, or none Driveway access density

Most Access Management Problems Happen Incrementally

Poorly managed corridors don’t happen overnight; they happen over many years

They often happen one decision at a time A series of decisions is usually involved in

degrading a corridor What can one more median opening hurt?

One more commercial driveway? One more traffic signal?

The problem is that all the small, bad decisions cumulate into one large problem—a “hairball”, to use computer programming slang

For another example of a specialty statewide model, see the second half of last week’s freight lecture.