TUESDAY'S accident on the Baltimore beltway illustrates the arbitrary nature of life. For 42 years, a footbridge spanned the busy road without incident. On Tuesday, at the height of rush hour, a truck -- one of thousands that pass through daily -- struck the bridge and it collapsed, killing one motorist and injuring three others.

Emergency personnel -- state and county -- responded with dispatch and skill. The injured were quickly attended to and transported to Maryland Shock Trauma Center. Police were able to divert heavy traffic through side streets.

The Maryland State Highway Administration organized and executed the demolition of the bridge and the cleanup of the debris efficiently. By Wednesday, motorists dealt only the typical inconveniences of a weekday commute.

The reinforced concrete bridge's structural condition, inspected by state officials last month, was sound. The bridge's clearance was 16 feet, 2 1/2 feet above the national interstate standard and high enough to allow properly loaded trucks to pass safely beneath it.

State highway officials believe a backhoe loaded on the truck struck the bridge's underside. They speculate that it gouged the concrete and steel reinforcing bars, weakening the structure.

With 23 footbridges over state roads and interstates, highway and trucking officials need to determine what can be done to prevent similar accidents. More attention needs to be paid to ensuring that trucks are properly loaded.