First responders practiced dealing with a simulated crash on the nearly completed Highway 99 tunnel in Seattle.

The exercise Thursday involved wrecked cars and buses in the northbound, lower level of the double-decked tunnel.

The federal Transportation Security Administration, which has supervised disaster exercises in many cities, provided advice about the scenario and observed the drill. A performance report could be published in about two months.

The 2-mile tunnel from Sodo to South Lake Union opens for public use in early February.