A 10-year-old boy and a 68-year-old woman were fatally struck by trucks in separate crashes on Tuesday, the third and fourth pedestrians to be killed by vehicles on New York streets in the first week of the new year, officials said.

The four pedestrian deaths were a grim start to 2020 after at least 122 people were killed while walking in 2019, when traffic-related deaths rose over all after having dropped for years amid a continuing push by Mayor Bill de Blasio to improve street safety.

Danny Harris, the executive director of Transportation Alternatives, a bicycle and pedestrian advocacy group, said the latest fatalities were a reminder that children and older people were among the most vulnerable to being hurt or killed by vehicles.

“Trucks keep getting bigger,” he said. “Humans are staying the same size.”

In one of the fatalities on Tuesday, the boy and his mother, 40, were hit by a city sanitation truck in Corona, Queens, shortly before 7 a.m., the police said.