Tristan Schulz is held by his mother, Mindy. Tristan was killed at 5 months old when he and his mother were struck by a Jeep in Loudoun County. (Aliyah Dastour/Alimond Studios)

A 5-MONTH-OLD boy, Tristan Schulz, was killed not long ago when the driver of an SUV plowed into his stroller as his mother was pushing it across a marked crosswalk in Loudoun County. At the time, according to what a witness told police, the SUV’s driver was holding up his cellphone, which may have distracted him. If so, Tristan’s tragic death fits a disturbing pattern of distracted driving that has contributed to the biggest surge in traffic deaths in a half-century.

The District, Maryland and at least 13 other states have enacted laws banning drivers from using handheld phones. But lawmakers in Virginia, where Tristan was killed, have rejected the idea more than once, ignoring extensive research showing that the use of handheld phones by motorists is dangerous.

All but a small handful of states, plus the District, now prohibit texting while driving, and at least 37 states, plus the District, ban all cellphone use for teenagers and other novice drivers. In addition, school bus drivers are forbidden to use cellphones in about 20 states.

Nonetheless, Americans like to be left to do as they please in their cars, so legislative resistance to regulating cellphone use has endured even as data have clarified the risks. In most states, drivers may still legally use handheld cellphones for purposes other than texting and emailing. Cellphone use leads to slower braking reaction time, drifting from lanes and increased tailgating, according to a World Health Organization survey in 2011.

The ongoing tolerance of cellphone use by drivers helped traffic deaths spike more than 10 percent in the first half of this year compared with the same period last year. And the United States’ 35,000 traffic deaths in 2015 represented the biggest increase since 1966.

A 2013 study by the Virginia Tech Transportation Institute indicated that while the specific act of talking on a cellphone may not directly increase the risk of accident, the associated activities — reaching for a phone, checking contacts, dialing and so forth — make crashes three times more likely. That study and similar ones were available last winter to Richmond legislators, who nonetheless killed a bill to ban the use of handheld cellphones in the General Assembly’s Transportation Committee.

Like most other states, Virginia has had a no-texting-while-driving law on the books since 2013. The trouble is that enforcement is all but impossible: Some drivers may say they were simply dialing their phones, which is legal in the state. That’s why it makes more sense to enact a flat ban on drivers using handheld phones — perhaps exempting only the use of a GPS device — which is more easily monitored and enforced by police.

Public education on the risks of cellphone use behind the wheel is valuable, but should be hammered home with legislation bearing stiff fines, possible loss of license and other sanctions. Those are common-sense moves to improve public safety and save lives.