A Washington state grandmother has written a thank-you letter to a state trooper in Idaho for giving her a speeding ticket in an exchange that she said on Thursday was a highlight of her recent holiday there.

Tana Baumler, 59, of Bothell, Washington, was driving her two grandchildren to Yellowstone National Park on July 6 when State Trooper Mike Nielson cited her for driving 91 miles per hour (146 kph) on a highway posted at 75 miles per hour (120 kph).

Baumler said Nielson was so courteous to her, and so solicitous of her alarmed grandchildren, aged four and seven, that she later sent the state police the handwritten note along with a check to cover the $155 penalty.

Nielson assured the children their grandmother was not in serious trouble and gave them so-called junior troopers stickers which all Idaho state police officers carry, Baumler said.

"He didn't leave me out and I got my very own sticker shock," she said in the thank-you letter.

"We were on vacation and he could have really dampened our mood but he was just great," Baumler told Reuters about Nielson.

She said the children asked if she was mad at the trooper for the ticket, allowing her to explain to them the importance of taking responsibility for one's actions.

"I told them grandma had made some poor choices and she had to pay the consequences," said Baumler.

Her granddaughter even urged Baumler to employ Nielson in the restaurant the family owns near Seattle.

"She told me, 'You need to hire him. He has good customer service,' " Baumler said.