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    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

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.