WATERVILLE — The city’s deputy police chief on Friday warned pedestrians and motorists to be cautious after three people were injured a day earlier in two separate and serious incidents while trying to cross streets where there were no marked crosswalks or lighted intersections.

A 28-year-old woman trying to cross Elm Street, west to east, at 12:05 p.m. Thursday near the Big Apple was seriously injured when she was struck by a motorcycle, according to Bonney.

“She was right in front of a southbound motorcycle,” Deputy Chief William Bonney said. “The motorcycle had no time to stop and he struck her.”

The motorcycle operator, Scott Haines, 41, of Fairfield, was charged with operating without a motorcycle endorsement, Bonney said.

The pedestrian suffered life-threatening injuries and was taken to Thayer Center for Health in Waterville and then by LifeFlight to Maine Medical Center in Portland. Bonney declined to identify her. Haines also was taken to the hospital with minor injuries, he said.

Maine State Police assisted city police with accident reconstruction and Bonney said he did not have a condition report Friday on the injured woman.

“We’re continuing to monitor her condition, but we don’t have any updates,” he said.

Meanwhile, shortly before 5:30 p.m. Thursday, a vehicle traveling south on College Avenue and changing lanes near Ash Street struck a woman, 21, and a man, 23, as they were trying to cross the avenue where there was no marked crosswalk, according to Bonney.

“The vehicle did not have time to stop,” he said.

The pedestrians suffered injuries not believed to be life-threatening and were taken to Thayer, and the man later was taken to Maine Medical Center in Portland, Bonney said.

He said police want to remind pedestrians that if they are not in a marked crosswalk or lighted intersection telling them to wait or walk, according to state law they do not have the right-of-way to cross a street and must yield to a vehicle.

“The law also says you can’t suddenly leave the curb and run into the path of a vehicle, and that’s basically what happened in each of these cases,” he said.

Bonney also noted that there is a lot of road construction underway in Waterville and large construction equipment can block the view of both motorists and pedestrians.

“Use additional caution when operating so you don’t find yourself in a situation where there’s a pedestrian in front of you and you don’t have time to stop,” he said.

Maine law, Title 29-A, section 2056, also says “when a vehicle is stopped at an intersection or a marked crosswalk to permit a pedestrian to cross, the operator of another vehicle approaching from the rear may not overtake and pass the stopped vehicle.”