Overview
The Iowa Department of Transportation (DOT) is conducting a planning study of the rural portions of the Interstate 80 corridor to best address safety and mobility needs of all freight and passenger travelers (Planning Study). This study is being conducted using the federally adopted Planning and Environmental Linkage (PEL) Study process. The Planning Study will allow near-term improvements to be planned, designed, and as funding is available, constructed in accordance with the long-term plan. As part of the Planning Study, an Automated Corridors study was conducted. The goals of the Interstate 80 Automated Corridors Study include:
- Leverage existing automated vehicle (AV) knowledge
- Help understand AVs and other transformative shifts in transportation
- Prepare for AV impacts on safety, mobility and travel time reliability in Iowa
- Plan for the future by considering the impact of AVs in the design of the proposed improvements
The guiding principles for the Planning Study include balancing mobility and access, designing for future needs, and right-sizing the corridor. These principles are the key reasons for the Interstate 80 Automated Corridors Study. Iowa envisions the future where advanced technologies make travelers safer and the transportation system more efficient and reliable. AVs are the primary technology to deliver these benefits.
As part of their vision, Iowa DOT will build smart corridors with communication and sensing technology to enable AVs to deliver increased safety and mobility benefits to travelers. AVs are vehicles enabled with technology that allow vehicles to control parts of the driving task, under a range of circumstances. This study employs the Society of Automotive Engineers definitions of the scale of vehicle automation from level zero to five (see Figure 2). Benefits include:
- Reducing the number of crashes related to human factors and weather
- Making significant improvements to highway capacity without the need for additional construction
- Reducing aggressive driving
- Improving travel efficiency and reliability
- Improving mobility to disabled and senior citizens
- Improving fuel efficiency through vehicle drafting
A needs analysis was conducted to account for AVs in the future Interstate 80 design. The study approach was driven by a set of conclusions and recommendations that were developed acknowledging the uncertainty involved with technology advancements and market adoption. This study considered multiple future scenarios (see Figure 5).Three primary factors were considered as part of the needs analysis; quality of peak traffic service, traffic safety and travel time reliability.
The study approach used a three-step method of scenario planning, scenario analysis and future-proofing. Scenario planning considered the range of possible futures and how likely trends may affect future transportation operations. From the scenario planning stage, four scenarios were advanced is: Early AV Adoption, Rise of the AVs, Limited AV Adoption, and AV Domination.
The analysis of each scenario informed the project team of the range of future design needs. Future-Proofing provided flexibility in the proposed design features, resulting in enhanced adaptability to future trends including AVs.
Conclusions were reached about how Interstate 80 might operate in the future at certain levels of AV adoption. Each of these findings will help Iowa DOT shape future agency policy and practices on how to deal with emerging AV technologies. Key to the study is several recommendations regarding Interstate 80 design and an additional study that should be completed to prepare Iowa DOT for AVs.
Key findings were identified for each topic area and provide Iowa DOT data that can be shared with others within the agency to lead to organizational awareness and impact policies related to AVs.
Key findings for each topic area include:
Scenario Planning
- AVs will serve as the primary vehicle type in the future. Design projects need to consider how current design practices might change to accommodate future trends including AVs.
- AVs are projected to substantially increase traffic demand. Traditional planning studies should include scenarios that examine the sensitivity of increased demand and its impact on corridor needs.
Traffic Capacity/Quality of Service Analysis
- Near-term analysis of AV adoption shows AVs in mixed traffic at lower levels of AV adoption do not show a decrease in segment average travel speeds.
- Mobility needs across most of Interstate 80 in the future will warrant six to eight lanes. Higher levels of automation show a substantial increase in the efficiency of Interstate 80 to carry higher traffic volumes.
Safety Analysis
- The safety analysis indicated that AVs are capable of preventing the majority of car crashes that occur on Interstate 80 today. The number of crashes per mile will decrease by 59% and the number of fatal and major injury crashes will decrease by 50% by 2040 assuming high levels of AV use. These crash reductions would happen even with traffic volume doubling.
Travel Time Reliability Analysis
- Without AVs and without widening Interstate 80, travelers will experience slightly longer delays in traffic.
- With AVs and after widening Interstate 80, travelers will experience more days without a slowdown.
Future-Proofing
- Future uncertainty needs to be considered in the design of Interstate 80 to provide flexibility
to operate under the full range of options identified in the scenario planning process.
A primary need of the overall Interstate 80 Planning Study is to identify the future needs of Interstate 80. The detailed analysis found in the Interstate 80 Automated Corridors Study generated a list of recommended changes to the Interstate 80 design to provide enhanced flexibility in the future.