A US police officer has revealed how he took an elderly woman out for dinner after she began driving dangerously during a marathon road trip.

Alabama officer Emanuel Dotch described his encounter with the woman in a Facebook post on October 10.

Mr Dotch says he was looking for somewhere to eat while driving on the Interstate 10 when he saw the woman “weaving all over her lane”, almost sideswiping a truck.

"They blew the horn and she eased over to the other lane, so I decided to pull her over to check on her,” Mr Dotch wrote.

Mr Dotch said upon further inquiry, he learned the woman was travelling from San Antonio, Texas to Pensacola, Florida - a distance of approximately 1160km.

Out of concern for the driver, Mr Dotch asked when she’d last eaten, before taking her to a Waffle House restaurant and paid for her meal, refusing the woman’s money on the basis it was his duty “to protect and serve” members of the public.

“So she asked me would I accept a hug and I told her I would do that,” he wrote.

The post is accompanied by a photo of the woman smiling while leaning against Mr Dotch.

Mr Dotch said the experience served as a reminder of the importance of looking out for one another.