A woman who got a wave from one motorist to go ahead and cross a St. Paul street was hit by a driver in another vehicle and critically injured Monday morning, police said.

The collision occurred shortly after 8:10 a.m. at the intersection of Maryland Avenue and Greenbrier Street, on the northeastern edge of the Arlington playground, said police spokesman Steve Linders.

The woman, in her 40s, was taken to Regions Hospital with “severe head injuries” that Linders described as life-threatening.

According to police:

A motorist in a vehicle “larger than an SUV” stopped in the right-hand lane of westbound Maryland and waved for the woman to the driver’s right to enter the crosswalk and on Greenbrier and continue walking south.

Once the woman was in the street, a compact car came along in the left lane of westbound Maryland — where there is no stop sign or signal light to obey — and hit the woman.

“She goes flying through the air and hits the pavement,” Linders said.

The car’s driver, a woman in her 20s, stopped immediately and cooperated with authorities. Linders said the driver did not appear to be impaired by alcohol or drugs.

For any motorist approaching an intersection, “if you see a car in the right-hand lane putting its brakes on and you see those brake lights, you need to be aware and ask why is that car stopping,” Linders said. “Be curious.”

Linders said the city has had more than 60 traffic crashes so far this year involving pedestrians or bicyclists.

He said police are in the midst of a “Stop for Me” publicity campaign in an effort to prevent people from being run over.

“We are trying to raise awareness,” he said “We need everyone working together; pedestrians, drivers, people on bicycles. … Every pedestrian crash is avoidable.”