An Iowa DOT assessment of potential ICM strategies.
Iowa, United States
Integrated Corridor Management - Des Moines Metro Area Phase 2 Strategy Bundle Evaluation
Summary Information
This Integrated Corridor Management (ICM) project focuses on developing operational strategies that will enhance safety, mobility, and travel time reliability for travelers in the Des Moines Metropolitan Area. The primary goals for this project are as follows: reduce fatalities and injuries, reduce travel time, improve traveler mobility, improve road and system efficiency, integrate multimodal transportation systems, improve accessibility, improve regional economic vitality, and maintain regional transportation systems. The ICM Project began in October 2018; the first phase identified ICM strategies that addressed current needs while the second phase developed a timeframe for implementing a hybrid bundle with associated strategies and evaluated medium to long-term strategies in terms of implementation ease, ICM benefits, and sequential order to determine relative timing (mid-range or long-range). The project is bounded by U.S. Highways I-235, I-80, I-35, Iowa 163, and any additional highways and arterials connecting to these freeways. The analysis utilized multiple predictive tools to evaluate competing packages of ICM improvement and conducted comparisons between different strategies based on the performance measures.
METHODOLOGY
Five bundling strategy concepts that range in their level of focus on roadway capacity, transportation system management and operations (TSMO) strategies, and transit capacity were developed to organize individual strategies by primary intention and functional area. The bundling concepts are as follows:
- Aggressive Freeway Build strategies focus on providing highway capacity improvements.
- Intensive Transportation Management focuses on arterial and freeway operations.
- Transit and Travel Demand Management focuses on high-occupancy transportation, transit service improvements, and trip reduction.
- Balanced strategies focus on both capacity improvements and operations management.
- Targeted Transportation Management focuses on lower investment levels of arterial traffic management.
The five bundles were analyzed against a number of performance measures and compared to two reference scenarios: 1) a Future No-Build Scenario that assumes that future population projections and land uses match those of the Des Moines Mobilizing Tomorrow plan without additional transportation system investments, and 2) a Planned Scenario that assumes that future population projections and land uses match those of the Des Moines Mobilizing Tomorrow plan and that the roadway
recommendations in the Des Moines MPO Long-Range Transportation Plan.
A regional travel demand model was used to estimate the amount of travel on regional roadways and transit lines. Estimates were based on projected regional population growth and employment, and results were presented in total amount of vehicle-miles traveled (VMT). Previous field observations of traffic volume, speed, and density were used to assess the operational efficiency of freeway facilities. Vehicle-hours traveled (VHT) were utilized to determine trip accessibility and overall traveler mobility. Linear regression was used to create a travel time reliability curve. Researchers utilized Iowa Department of Transportation crash rates to estimate expected crash frequency.
FINDINGS
- Balanced and Intensive Transportation Management strategies had the highest overall improvement across safety, mobility, reliability, integration and connectivity, accessibility, and systems management.
- Implementing Transit and Travel Demand Management strategies increases the transit mode share from 1.3 percent (under the Future No-Build scenario) to 3.4 percent. Implementing this bundle reduces peak period vehicle-miles traveled (VMT) by 1.5 percent, reducing AM/PM peak period traffic volumes by approximately 165,000 trips.
- Targeted Transportation Management, Intensive Transportation Management, and Balanced bundles improved job accessibility by 5.8 percent, 6.2 percent, and 6.5 percent respectively. The Transit and Travel Demand Management bundle improves accessibility by 8 percent.
- Transit and Travel Demand Management, Targeted Transportation Management, Balanced, and Intensive Transportation Management bundles reduced fatal and serious injury crashes by 8 percent, 9 percent, 10 percent, and 11 percent respectively.
- The Targeted Transportation Management bundle reduces AM and PM peak period VHT by 13 percent, and Intensive Transportation Management and Balanced bundle strategies both reduce it by 16 percent.
- Targeted Transportation Management, Intensive Transportation Management, Balanced, and Aggressive Freeway Build bundles improved system reliability by 4.6 percent, 5.5 percent, 8.2 percent, and 9.5 percent respectively.
The percentage improvements in roadway safety, mobility, reliability, integration and connectivity, accessibility, and systems management by bundle are summarized below in Table 1.
Table 1. Percentage Improvements by Bundle Strategies.
|
|
Safety |
Mobility |
Reliability |
Integration and Connectivity |
Accessibility |
Systems Management |
|
Balanced |
10% |
28% |
6% |
< 0.5% |
6% |
< 1% |
|
Intensive Transportation Management |
9% |
26% |
6% |
0.5% |
6% |
1% |
|
Transit and Travel Demand Management |
8% |
4% |
0% |
2% |
8% |
1.5% |
|
Aggressive Freeway Build |
3% |
16% |
4% |
< 0.5% |
2% |
-1% |
|
Targeted Transportation Management |
7% |
20% |
5% |
< 0.5% |
6% |
> 0.5% |
