The Case for Connectors

Using freeway rather than interstate standards would allow cities, counties, and states to afford expansion.

Source: PUBLIC WORKS MAGAZINE
Publication date: 2009-04-01

By Martin Weiss

The desire for growth drives local governments to pursue interstate designation of highways, and since 1995 Congress has identified about a dozen — mostly rural corridors — as future interstates. Yet in the past eight years fewer than 100 miles have been added to the Interstate Highway System each year. During the 1990s about 200 miles were added annually, and about twice that many were added in the 1980s.

What happened?

The system has gone through many changes in its 50-year existence. In 1968 Congress decided that highways built with funds other than those set aside for interstate construction still could be designated as interstate highways. Even so, most were built through the Interstate Construction Program, which hasn't received an appropriation since 1996.

Congress had been identifying previously designated high-priority corridors as future interstates, and when the Safe Accountable Flexible Efficient Transportation Equity Act – A Legacy for Users (SAFETEA-LU) was enacted in 2005, it designated more than 4,000 miles of future interstates. The funding that would be required to build these roads is beyond the limit of any realistic restructuring of the federal highway program.

One cost-effective way to continue construction is to designate future interstates as “interstate connectors” and design them to American Association of State Highway and Transportation Officials (AASHTO) standards for non-interstate freeways, which are used for freeways on the National Highway System (NHS), rather than AASHTO's interstate standards.

The connectors would carry signing similar, but not identical, to an interstate shield. Other than that, there are three major differences between the two sets of standards. The interstate standard requires a higher vertical clearance for bridges, greater spacing between interchanges, and federal approval of all design exceptions.

Mapping the futureThe National Highway System has designated 12 highway corridors as future interstates.Giving states the option of obtaining an interstate connector designation for routes designated as future interstates once they achieve AASHTO freeway standards would save billions over the long term with minimal impact on safety.Map: Federal Highway Administration

There's a legitimate need for a solution that involves a reduction in cost as opposed to simply an increase in expenditures.

Consider State Route 99 (SR 99) in California between Sacramento and Bakersfield, which Congress designated a future interstate in 2005. In 2006, the California DOT (CALTRANS) developed a business plan for improving a segment between Bakersfield and Stockton totaling more than 90% of the corridor. Developed with local governments and municipal planning organizations, the $5.5 billion plan's priorities include widening critical freeway sections and adding interchanges.

In 2005 CALTRANS estimated that improving about 270 miles of the route to interstate standards would require an additional $10 billion to $15 billion. Although the agency expects more exceptions to the standard — particularly in regard to bridge vertical clearance and interchange spacing — the additional cost may still be $1 billion to $3 billion.

Similar situations exist in Kentucky, New York, Pennsylvania, Texas, and Tennessee, where designated future interstates could be “built” by upgrading existing highways.

Other types of highway connectors already exist. There are connectors to major intermodal terminals such as airports, seaports, and rail facilities and connectors to defense assets. Improvements are eligible for National Highway System funding, but there are no national design standards for either type of connector and no national standards for NHS routes other than those on the interstate system.

Existing language that limits funds from the Interstate Maintenance Program to full interstate highways shouldn't be eliminated, providing an incentive to improve interstate connectors to full interstate highways. The mileage on interstate connectors also wouldn't be included in the formula used to apportion Interstate Maintenance Program funds, providing another incentive to improve such connectors to full interstate highways.

The major advantage of designating interstate connectors is that states would be able to apply signing to limited-access highways sooner and at substantially lower costs than without such a designation. Such signing would also allow more logical exit numbering and perhaps save travelers from making errors in finding destinations.

The major disadvantage is that it could reduce the rate at which freeways are improved to full interstate standards because it could be perceived as lowering the incentive to do so.

Critics may argue that allowing interstate connectors will be detrimental to safety.

But in the last three years the fatality rate on SR 99 has been about the same as that on I-5, which roughly parallels it to the west. The total crash rate on SR 99 has been about 40% higher than on I-5 mostly because of the character of the traffic: SR 99 has about 30% more volume and goes through urbanized population centers in the San Joaquin Valley. With the improvements already programmed for SR 99, both the fatality and crash rate will likely decrease.

In addition, funds saved by improving SR 99 to the freeway rather than the interstate design standard could be used to improve the safety of other highways.

— Martin Weiss (mhw20854@yahoo.com) is retired from the Federal Highway Administration, where he worked on interstate designation and numbering. Alan McCuen (alan_mccuen@dot.ca.gov) is former deputy director of the California DOT district that includes Fresno.