As state Rep. Marilyn Lee was walking through her Mililani neighborhood, she noticed a toddler sleeping alone in a car while the child's parents played tennis nearby.

That incident got the nurse and grandmother of two thinking that stricter laws were necessary to prevent tragedies such as the recent death of 3-year-old Sera Okutani, who died after she was left alone in a car for more than 1 1/2 hours last month.

"People have to understand, when you're a parent, you have the responsibility for the care of someone who is helpless, and the responsibility to do everything you can to make sure they're safe," Lee said.

For the past five years, Lee has been pushing to pass a law that would levy penalties against those who leave children alone in cars.

A day before her bill was to be heard by the state Senate Transportation Committee last month, little Sera died, adding relevance and urgency to Lee's message.

Last week, 1-year-old Maylani Piper-Caravalho, of Kailua, Kona, was killed when a sport utility vehicle ran over her while reversing in a driveway. And on March 8, 2-year-old Teysia Aku, of Punalu'u, was run over in a driveway by a reversing SUV and died.

According to the state Department of Health, 13 children have died in such incidents since 1991. Two children in that same period have died after they were left unattended in cars.

"That's 5 percent of all injury-related deaths for children in that age group. That's pretty high — almost one a year," said Dan Galanis, epidemiologist with the DOH Injury Prevention and Control Program.

Accidents can be prevented, said Su Yates, director of Keiki Injury Prevention Coalition: Parents just need to take extra steps to ensure their child is accounted for at all times.

Reach Loren Moreno at lmoreno@honoluluadvertiser.com.