The ICM AMS Test Corridor
The analysis team selected the San Francisco Bay Area’s I–880 corridor to serve as the testbed for the AMS methodology after a careful review of more than 20 candidate corridors. This corridor is one of the main arteries in the San Francisco Bay Area, with 38 miles of freeway connecting Silicon Valley with the East Bay. It is a major freight and passenger throughway serving the Port of Oakland, Oakland International Airport and the Oakland Coliseum, as well as a concentration of residential, industrial and commercial properties. The team also selected the I–880 corridor because of the wealth of available corridor data, multitude of transportation modes and facilities (freeways, arterials, high-occupancy vehicle (HOV) lanes, transit, etc.) and the transferability and applicability of results and methods to other corridors.
Operational Conditions of the Test Corridor
The ICM AMS framework provides tools and procedures capable of supporting the analysis of both recurrent and nonrecurrent corridor operational conditions. In the test corridor AMS effort, nonrecurrent congestion conditions entailed combinations of increases of demand and decreases of capacity. Key ICM impacts may be missed in analysis if only “normal” travel conditions are considered. As shown in Figure 3, the different operational conditions of the AMS approach take into account medium- and high-travel demand, combined with assumptions of major and minor incidents.
The relative frequency of nonrecurrent conditions is important to estimate in this process—based on archived data. Figure 3 shows the overall frequency of various operational conditions for the test corridor, including percentage of days in the year categorized by different incident and demand levels. Major incidents were defined as having duration more than 20 minutes, and minor incidents as having duration less than 20 minutes. In the test corridor, major incidents together with high demand, characterize 25 percent of all workdays (red or upper-right cluster in the left part of Figure 3), while 22 percent of all workdays (green or lower-left cluster) feature both low demand and minor incident conditions. The right part of Figure 3 shows that 39 percent of total annual delay (red or upper-right cluster) occurs on the worst 25 percent of days, while 64 percent of annual delay (red and yellow) occurs on the worst 44 percent of days. Conversely, only 14 percent of annual delay (grey and green) occurs on the remaining 39 percent of days.
Performance Measures Used in AMS of the Test Corridor
USDOT is working to establish a continuous improvement cycle to apply to the integrated management and operations of transportation assets in our nation’s multimodal corridors. Figure 4 depicts a process in which by defining clear corridor level performance objectives, archiving operations data and analyzing the impacts of ICM strategies, transportation agencies can improve the performance of their corridors.
Better data leads to better models leads to better investment, and so on.
To be able to compare the impacts of different ICM strategies within a corridor, analysts applied a consistent set of performance measures to the AMS test corridor effort. These performance measures:
- Provide an understanding of travel conditions in the study area;
- Demonstrate the ability of ICM strategies to improve corridor mobility, throughput, reliability and safety based on current and future conditions; and
- Help prioritize individual investments or investment packages within the test corridor for short- and long-term implementation.
To the extent possible, the measures were reported by:
- Mode – Single-occupancy vehicle (SOV), HOV, transit, freight, etc.;
- Facility Type – Freeway, expressway, arterial, local streets, etc.;
- Jurisdiction – Region, county, city, neighborhood and corridor-wide.
The performance measures focused on the following five key areas:
- Mobility – Describes how well the corridor moves people and freight;
- Reliability – Captures the relative predictability of the public’s travel time;
- Safety – Captures the safety characteristics in the corridor, including crashes (fatality, injury and property damage);
- Emissions – Captures the impact on emissions consumption; and
- Fuel Consumption – Captures the impact on fuel consumption.
For the identified ICM strategies, the analysis team prepared planning-level cost estimates, including life-cycle costs (capital, operating and maintenance costs). Costs were expressed in terms of the net present value of various components.