Truck Bypass

Description of Project

The California Department of Transportation (Caltrans) has developed plans for a westbound truck bypass on a new alignment for a distance of just over six miles. The bypass would run from the Interstate 205 (I-205) Mountain House Parkway Interchange in San Joaquin County to a point west of the Interstate 580 (I-580) Grant Line Road Interchange in Alameda County. The truck bypass will be two lanes wide with a left shoulder width of 1.5 meters and a right shoulder width of 3.0 meters, standard for a freeway-to-freeway connection.

Purpose of Project

This new facility would allow truck traffic on I-205 to bypass a sustained 3% upgrade with mixed-flow traffic as well as the weave on I-580 just before the Grant Line Road off-ramp. The bypass will merge with mainline I-580 west of Grant Line Road at a point where the high truck volumes can be safely accommodated with appropriate merging distance. Lane drops on the new bypass will be placed as appropriate to maximize safety and efficiency when merging truck traffic back onto the main line.

According to Caltrans, the project will:

    • Relieve traffic congestion and improve safety and operational efficiency by separating slow-moving vehicles from the rest of traffic.

    • Improve freight and goods movement between the Bay Area and the Central Valley.

    • Reduce movement conflicts.

    • Remove a choke point and improve reliability of goods delivery.

Uses of the Results

Caltrans used this analysis to compare the benefits and costs of the project with a no-build scenario.

Agency Perspective

Caltrans owns and maintains I-205 and I-580, which are included in the Interregional Road System (IRSS). The westbound truck- climbing lane project was part of the near-term improvements recommended in the "Altamont Interregional Corridor Transportation Study" and "I-205/I-580 Corridor Study". The operational and safety improvements proposed by this project are consistent with the concept of an eight-lane facility for I-205 and a six-lane facility for I-580 with truck separated facilities identified as options on both corridors, and would not preclude future transportation improvements in the project area.

Base Case

The base case in this analysis is doing nothing. The sustained upgrade profile averaging 3-4% within the segment of roadway will continue to have an adverse impact on operating speeds of large trucks and other vehicles. The westbound I-205/580 is currently near capacity and will continue to have a declining level of service unless capacity is increased.

Alternatives Considered

The only alternative considered to the no-build case is the truck bypass.

Type of Analysis

The Office of Transportation Economics used the California Life-Cycle Benefit/Cost Analysis Model (Cal-B/C) to calculate the project's life-cycle cost, life-cycle benefits, net present value, benefit/cost ratio, internal rate of return, and payback period.

Geographic Scope

The proposed project is located between 300 meters west of the I-580 Grant Line Road Interchange in Alameda County and the I-205 Mountain House Parkway Interchange in San Joaquin County. I-205 and its connection with I-580 west of the City of Tracy provide east-west interstate freeway and truck linkage between the Central Valley and California's Pacific Coast. It is a major link in the east-west corridor between Routes 880 and 99 connecting the San Francisco/East Bay Area and Livermore Valley with the Stockton/Central Valley area. It is also a major recreational route, providing access to and from the Bay Area, the San Joaquin Delta, and the Sierra Nevada Mountains.

I-580 is an interstate freeway beginning at I-5 southwest of Vernalis and ending at Route 101 in San Rafael, excepting a portion from Oakland to Albany (Route 80). It is an important truck route serving the Los Angeles-San Francisco Bay Area corridor as well as the Central Valley-Bay Area corridor via I-205.

Time Period for Analysis

The time period for the analysis is 20 years.

Benefits, Magnitude, and Value

The benefits considered for this project are those benefits monetized in the Cal-B/C Model. For a more in-depth explanation of the parameters used in Cal-B/C, see The California Life-Cycle Benefit/Cost Analysis Model (Cal-B/C) Technical Supplement to User's Guide (Booz-Allen & Hamilton 1999). All benefits and costs are in year 2000 dollars. A 5.0% discount rate was used to evaluate future costs and benefits in 2000 dollars.

Travel time was valued at $8.16/hour for automobiles, $27.72/hour for trucks.

Vehicle operating costs were divided between fuel and non-fuel related costs. Fuel costs were valued at $1.14/gallon. Non-fuel related costs were valued at $0.165/mile for automobiles and $0.285/mile for trucks.

For a detailed list of accident cost parameters, see The California Life-Cycle Benefit/Cost Analysis Model (Cal-B/C) Technical Supplement to User's Guide (Booz-Allen & Hamilton 1999).

Emission benefits were not conidered in this analysis.


The initial cost estimate for this project was $58.4 million, with an average future maintenance and operation cost of $169,000 per year. This project is currently programmed for Project Approval and Environmental Document (PA&ED) phase only. Future funding to complete the project is expected primarily from the Interregional Transportation Improvement Program (ITIP); however, there is potential regional local funding for future phases.


The following tables present the results of the Cal-B/C analysis:

Sensitivity Analysis Performed

The user can conduct a simple sensitivity analysis by changing traffic projections or other factors in Cal-B/C and compare the B/C results for the range.

Models Used

Cal-B/C was used for this benefit-cost analysis.

Critique — Strengths and Weaknesses

Strengths of Cal-B/C:

    • Provides quick response to upper management for preparing a simple economic analysis of both highway and transit projects.

    • Cal-B/C is a practical tool for comparing roadway and transit alternatives with similar benefits and for ranking a large number of proposed projects.

Weaknesses of Cal-B/C:

    • The model cannot estimate benefits for a specific group of users (other than passenger vehicles and trucks).

    • Cal-B/C lacks the capability to estimate network effects, although regional travel models can incorporate such effects indirectly.


The information for this case study was provided by Caltrans.