If youi were one of the thousands of motorists trapped on the Beltway Monday evening, you will not have pleasant memories of the event. If your family was hustled away from the dinner table to an evacuation center at Edison High School, you probably wouldn't want to go through such an evening again soon. But even those most inconvenienced by the chemical leak that disrupted rush-hour traffic will have to agree that those responding to the hazardous situation seem to have done an extraordinarily good job.

Let's start with the anonymous, alert citizen who was driving behind the truck that was transporting the hazardous chemicals. That motorist not only spotted the leak and realized that it might be dangerous, he also took the trouble to flag down the truck and warn the driver. Police and fire personnel arrived in record time and completed the task of shutting down 21/4 miles of the Beltway. The tracks of the Richmond, Fredericksburg & Potomac Railroad near the scene were also closed off as a precaution. The Fairfax County Fire Department's special hazardous-materials unit was on the scene and, in cumbersome astronaut-type suits, proceeded to do their job.

There were no serious injuries and no explosion. Uprooted residents were given dinner at the evacuation center and Red Cross workers were prepared to house them for the night. Everything seemed to click and to work smoothly. Volunteers and public employees all did a superb job. They demonstrated the calm competence and ability to perform well under pressure that are essential in a crisis -- even in a potential crisis like this. Congratulations are in order.