Paul Hoile, who has since resigned as a special constable, said the sexual activity was consensual.
A former police officer has been cleared of raping a woman by a roadside while off duty.
Paul Hoile, who was a special constable with the Metropolitan Police at the time, had in total faced five charges in connection with his interaction with her in Shropshire in July.
During the trial, he told the jury at Wolverhampton Crown Court that the sexual activity was consensual.
The 40-year-old was found not guilty on all counts on Friday.
He had been accused of three counts of rape, one of misconduct, and causing a person to engage in sexual activity without consent.
The prosecution alleged Mr Hoile, from Essex, had used his warrant card while drunk to “exert control” over the woman, “inappropriately interrogate” her, and compel her to answer questions.
The defendant said he had produced his warrant card at the request of the woman and disputed claims he had snatched her phone.
‘Without fuss’
He also denied the woman’s account that he had instructed her not to drive.
Mr Hoile, who had since resigned from the Met, told the jury he had “stupidly” propositioned the woman, but that sexual activity took place consensually and “without fuss”.
He said she had performed a sex act on him by the side of the road, before further activity took place near a fence in a “dark lane”.
Following his acquittal, he was allowed to personally thank the jury members from the dock after asking to speak.
Judge Jonathan Gosling also thanked the jury, saying they had faced “incredibly difficult decisions to take”.
He added the defendant still faced a further indictment relating to a single allegedly indecent image – a charge he described as a “menial matter by comparison” and granted Mr Hoile bail.
Follow BBC West Midlands on Facebook, Twitter and Instagram. Send your story ideas to: newsonline.westmidlands@bbc.co.uk