In many legislatures, including Oklahoma’s, the concerns of such scientists have made little impression.

Concerns About New Rules

In February, five months after the accident that killed Ms. Doyle, Sue Tibbs was in Tulsa undergoing one of her regular seven-hour chemotherapy treatments for ovarian cancer.

As an Oklahoma state representative, Ms. Tibbs was finishing a bill to require hands-free devices for drivers and to ban texting while driving. She had developed an interest in the issue last fall, after hearing about a growing number of crashes like the one involving Mr. Hill and Ms. Doyle, and after an Oklahoma state trooper told her he was increasingly concerned about multitasking behind the wheel.

As Ms. Tibbs sat in the cancer center, she overheard a conversation that sealed her resolve. A woman nearby talked of how her husband often became so engrossed in his cellphone calls he would miss the turn for the road to their home. The cellphone, Ms. Tibbs decided, isn’t like other distractions. “When you’re eating, you’re not concentrating like when you’re on the cellphone,” she said.

On Feb. 19, the public safety committee voted 8 to 4 to send Ms. Tibbs’s bill to the full legislature. She was thrilled. But on March 12, the last day her bill could be considered, the majority floor leader, Mr. Jones, hadn’t brought up her bill. That night, she asked Mr. Jones, a fellow Republican, why. He explained that there was too much opposition, she said. Later, Ms. Tibbs said, he added another reason: she was fragile from cancer and he didn’t want her to go through a long-shot battle for the bill.

Mr. Jones, in an interview, said he and his colleagues needed more evidence of the dangers before they considered restricting the freedom to talk while driving. “We’re concerned about going into the cellphone realm at this point,” he said, adding that he was not lobbied by any companies that make money from the use of devices in cars.

But he said he recognized from using his phone while driving that it could be dangerous, particularly when dialing. “There’s definitely a time when you’re looking at your cellphone,” said Mr. Jones, who uses a hands-free device. “If you’re going to do it, you have to be extremely cautious.”