If you’ve found yourself on one of the many on and off ramps in Northern Virginia, you’ve undoubtedly accidentally come upon a roadside emissions test. You can typically tell since the roadside sign warns you that your vehicle is quickly approaching one to two forest green boxes with sniffers pointed at your exhaust.

Most “modded car guys” who love to hear the sound of their engine over the radio dread these roadside mobile emissions tests thinking that their intended purpose is to generate ticket revenue through fines for vehicles with high emissions. But no fear – these emissions testers can’t actually issue tickets (more on that later), but rather a handy alternative to driving the whip to a gas station for the biennial emissions test required in the state. The temporary roadside sniffers have been implemented since December 2015 and are run by a third party entity called RapidPASS (owned by ETEST).

Driven by the Virginia air quality initiative, Air Check Virginia, the RapidPASS equipment enables qualified, compliant drivers registered in the state of Virginia (vehicles registered out of state will not be tested or notified) to simply drive past the emission tester to receive an emissions test without having to go to the local mechanic’s shop. If your vehicle passes, you will be mailed a qualification letter that you can enter online through RapidPASS’s online portal to pay the fee of $28 and receive your emissions inspection certification.

To qualify, the RapidPASS website recommends driving past the mobile testers frequently starting 120 days before your emissions test is due (before that time, you will not receive a qualification letter as this is too early to apply for vehicle emissions test in VA). Drivers can find the ever-changing locations of the sniffers from the RapidPASS website. Note – the testers are affected by inclement weather, so check before you head out if rain’s in the forecast.

“But I’ve driven past these and never received a letter?” You may not have registered on the system (which is why they recommend driving by more than once), or perhaps you didn’t pass. If you think you may not be eligible for the roadside test despite driving past one, you can check via their site – you’ll need your license plate number and the last 4 digits of your VIN.