Traynor said most current cellular networks send messages individually, meaning a system like Virginia Tech’s would require thousands of texts to go out one by one. As cellular broadcast technology improves, Traynor said, emergency messages will be able to go out to subscribers at the same time.

If local networks are bogged down by thousands of messages that eclipse network capacity, emergency cell-phone calls from students or professors could be blocked, cutting people off from police and fire departments, Traynor said.

“The messages go out one at a time, and there’s nothing that the companies can do to improve that,” Traynor said. “These campus text systems can actually cause more problems than they solve.”

Karla Lemmon, a program manager for New Jersey-based Honeywell International, which makes alert systems for K-12 schools and colleges, said mass text-message blasts will bog down a cell tower, but broadcasting messages from a host of servers makes text delivery more reliable.

More than 2,600 schools nationwide use Honeywell’s Instant Alert system to send automated phone calls and text messages, and about 230 college campuses have adopted the product’s higher-ed model, Lemmon said.

Industry experts said the technology is still being perfected in tests nationwide. Lemmon acknowledged that she conducted a text-message test last summer in which one message didn’t reach her for three weeks.

“It’s not necessarily always the fault of the provider,” she said. “Delays in text-message systems can happen at any time, on any day.”

Last year, researchers at Purdue University tested the school’s emergency text-alert system and found that 4 percent of nearly 10,000 text messages failed to transmit. That means about 400 students and faculty members wouldn’t have received an emergency message via cell phone.