6.0 Conclusions and Recommendations

Our conclusions from the analysis of highway truck bottlenecks are as follows.

Highway truck bottlenecks can be identified and differentiated from general traffic bottlenecks. A relatively comprehensive inventory of highway truck bottlenecks can be made using available FHWA Highway Performance Monitoring System (HPMS) data and Freight Analysis Framework (FAF) data.

The impact of the highway truck bottlenecks can be measured by total truck hours of delay, hours of delay to large trucks making longer-distance trips, and the tonnage and value of the commodities in the trucks. These measures provide a good relative ranking of individual bottlenecks, but because of data and analysis limitations, they do not provide absolute measures of the truck hours of delay at each bottleneck. For example, at highway interchanges, the current analysis methods account for truck hours on the critically congested highway, but not on the intersecting highway or arterial roadway. Moreover, the analysis methods do not yet adequately account for the congestion effects of traffic weaving and merging at on- and off-ramps. These limitations cause the total truck hours of delay to be underestimated.

Highway truck bottlenecks accrue significant truck hours of delay, totaling upwards of 243 million hours annually. At a delay cost of $32.15 per hour, the conservative value used by the FHWA's Highway Economic Requirements System model for estimating national highway costs and benefits, the direct user cost of the bottlenecks is about $7.8 billion per year.

Of the four major types of bottlenecks studied (interchange, steep-grade, signalized-intersection, and lane-drop bottlenecks) interchange bottlenecks account for the most truck hours of delay, estimated at about 124 million hours annually in 2004. The direct user cost associated with interchange bottlenecks is about $4 billion per year.

The truck hours of delay caused by individual highway interchange bottlenecks are significant. The top 10 highway interchange bottlenecks cause an average of 1.5 million truck hours of delay each. Of the 227 highway interchange bottlenecks, 173 cause more than 250,000 truck hours of delay annually. By comparison only a few dozen of all the other truck bottlenecks cause more than 250,000 truck hours of delay annually. The number of bottlenecks by type accruing over 250,000 annual truck hours of delay are as follows:

• Highway interchange bottlenecks (based on HPMS Universe database) – 173
• Steep-grade bottlenecks (based on HPMS Sample database only) – 12
• Lane-drop bottlenecks (based on HPMS Sample database only) – 1
• Signalized-intersection bottlenecks (based on HPMS Sample database only) – 2

Highway interchange bottlenecks are of Federal interest because they are a significant national problem for trucking and the efficient operation of the national freight transportation system. Highway interchange bottlenecks affecting trucking are widely distributed across the United States along Interstate freight corridors of national significance. The primary truck delay on these nationally significant routes is in the major urban areas, including major international trade gateways and hubs such as Los Angeles, New York, and Chicago, and major distribution centers such as Atlanta, Dallas-Fort Worth, Denver, Columbus (Ohio), and Portland (Oregon). These urban interchange bottlenecks create sticky nodes that slow long-distance truck moves along Interstate and other National Highway System regional, transcontinental, and NAFTA freight transportation corridors.

Our findings and conclusions suggest that FHWA may wish to consider the following recommendations.

The FHWA should work closely with the states, metropolitan planning organizations, and industry to monitor truck delay at urban Interstate interchange bottlenecks on freight routes of national significance. As part of its strategic and performance planning efforts, FHWA has begun an effort to identify nationally significant freight routes and measure performance over time on these corridors. More accurate information on delays at highway interchanges will help the FHWA and carriers understand the contribution of interchange delays to overall travel time and reliability in these corridors.

The FHWA also should work closely with states and metropolitan planning organizations to focus Federal highway improvement and operations programs on highway interchange bottlenecks. The Federal highway improvement and operations programs would include existing programs such as the core Federal-aid highway programs for Interstate Maintenance and NHS and discretionary programs such as the Corridors program and ITS Deployment program. The FHWA also should focus new freight programs such as the Projects of Regional and National Significance program and the Truck Lanes program on highway interchange bottlenecks.

To support these policy and program actions, the FHWA should continue the development of data and analytical methods to better estimate truck hours of delay at highway bottlenecks. Specific initiatives would include the following:

• Re-estimate truck hours of delay at highway interchanges using the next-generation methodology being developed for the Ohio Department of Transportation. This methodology will better account for delays caused by traffic merges and weaves at interchanges and capture delays on all legs of an interchange.
• Develop procedures to estimate the exposure of trucks to congestion by time of day. The current generation of delay estimation methods assumes that the distribution of long-distance truck trips is similar to the distribution of short-distance automobile and service truck trips; that is, they are concentrated during the morning and evening peak commute periods. Research studies and anecdotal evidence suggest that many long-distance truck trips are scheduled to avoid peak-period urban congestion. This would tend to reduce truck exposure to congestion and reduce truck hours of delay. More information is needed on the time-of-day distribution of truck trips and the actual exposure of trucks to congestion.
• Consider developing a spatially enabled interchange database that would support safety- and congestion-related analyses including the following truck-specific initiatives: re-estimate truck hours of delay at highway interchanges using the next-generation methodology to better account for delays caused by traffic merges and weaves at interchanges and capture delays on all legs of an interchange; and develop procedures to estimate the exposure of trucks to congestion by time of day.
• Estimate the cumulative, corridor-level impact of closely spaced bottlenecks on longer distance truck trips. The current analysis treated each bottleneck as an independent event.
• Conduct case studies to trace and explain the supply chain and economic impacts of highway truck bottlenecks. The case studies should examine how motor carriers adjust to bottleneck delay, examine how delay costs are passed on to shippers and consumers, and estimate the economic costs of delay by industry sector.
• Inventory and track current and planned improvements that would reduce future delays to trucks at the 200 most significant highway interchange bottlenecks. The tracked improvements would include construction of new by-passes, redesign of existing interchange, implementation of ITS (intelligent transportation systems) services, improved operations such as better incident management, introduction of managed toll lanes open to trucks, etc.

Highway interchange bottlenecks are a significant problem today and will become a bigger problem in the future. We recommend that the FHWA continue its initiatives to focus on freight bottlenecks and develop policies and programs that will reduce the costs of delay.