VIRGINIA BEACH, Va. (AP) — Four hospitals created a mobile emergency department out of a series of interlocking tents to treat runners and spectators at the Rock 'n' Roll Half Marathon in Virginia Beach.

Sentara Virginia Beach General Hospital says just over 100 people were treated, mostly for heat-related illnesses and cramping, over less than three hours Sunday. The hospital says this marked the first time in Virginia that disaster tents owned by virtually every hospital in the post 9/11 era have treated actual patients, not just actors in a drill.

Sentara ER nurse Christopher Roberts says it mimics exactly what it would be like in a real mass casualty event.

Three Sentara hospitals and Rappahannock Hospital created the mobile ER to reduce travel time and speed of treatment for runners.