Masturbate, but...

You get into your car and start driving. Once on the main road, you grab the dildo from your purse. You slide the front portion of your skirt aside, giving access to your wet pussy. You slide the dildo into you and slowly start fucking yourself with it. You arrive at a particularly long red light and you let yourself get lost in the feeling of the dildo sliding in and out of you. You reach your other hand under your tank top and above your breasts as you start toying with your nipples. You close your eyes as you near climax. You are about to cum.

(Almost there, just a few more-)

A knock at your window snaps you out of it. You look and see a cop standing there. You quickly roll down your window.

"Ma'am, why are your breast out?" He asks.

You panic and reach to lower your top back down.

"Don't make any movements without me telling you to first." He says, stopping you. "Keep your hands on the steering wheel."

You obey.

"Now, why are your breasts out and..." He reaches into your car and pulls your thighs a little more apart "Why is there a dildo inside you?"

You decide that honesty is likely the best option.

"I was really horny, but I was running late so I had to-"

"Had to?" He interrupts.

"I wanted to cum before I got to work and this was the only way I could... well, think of."

"I see. How close to cumming did you get?" He asks.

"I was about to cum when you knocked."

"Okay, hmm, show me what you were doing, exactly."

"What?"

"Masturbate how you just were, tell me when you are about to cum."