Cesar Martinez had just made a wrong turn due to a dying GPS when he noticed an errant Wallingford-Swarthmore school bus careering into bushes, knocking down street signs, and traveling across suburban front lawns.

As the back of the bus swung about wildly, "I thought it was going to flip over," Martinez recalled. He immediately called 911.

With the help of his older sister, Yolanda Martinez, calling out the street names, Martinez, 39, of Norristown, stuck with the bus and was able to keep police abreast of the situation.

Police pulled over the bus on the sidewalk near Yale Avenue and Chester Road in Swarthmore. One passenger, a 16-year-old boy, was aboard. He was not injured.

"The kid was really shaken up," Brian Craig, Swarthmore's chief of police, said. "The officer spent a lot of time telling him it was OK to get off the bus."

The driver, Christine Rogers, 48, of Brookhaven, was charged with driving under the influence and related crimes in the Monday incident, according to Craig.

Craig said the arresting officer detected a strong odor of alcohol. He said an empty vodka bottle was found in Rogers' purse next to the driver's seat.

"Don't do this to me," Rogers allegedly told police when asked how much she had to drink.

Police field-tested Rogers, who had a preliminary blood-alcohol level of 0.374, according to Craig. That's more than four times the legal threshold for intoxication, 0.08. He said officers at the scene transported her to an area hospital, where she was admitted.

Wallingford-Swarthmore School District officials declined to comment.

Contact staff writer Mari A. Schaefer at 610-892-9149 or mschaefer@phillynews.com.