Should I Get a Speedometer Calibration for a Reckless Driving Charge in Virginia?

Sometimes, and it’s a decision to make with your lawyer. A speedometer calibration checks whether your car’s speedometer shows your true speed. If it reads low, displaying a slower speed than the car was actually traveling, the report can help explain why you didn’t realize how fast you were going. That makes it mitigation, not a defense. It doesn’t change the speed an officer measured with radar or lidar, and a speedometer that reads accurately or high may not help at all.

If you are still working out what the charge itself means, start with our explanation of what reckless driving is in Virginia.

What a calibration tests

A shop typically runs the car on a dynamometer, a set of rollers that measures how fast the wheels are actually turning, and compares that speed with what the speedometer displays at several test speeds. The report shows whether your speedometer reads low, reads accurately or reads high, and by how much at each speed tested.

That result is about your dashboard, not the officer’s measurement. Radar and lidar measure the car directly. Your speedometer’s error bears on what you saw while driving, which is a different question from how fast the car was going.

What Virginia law says about the report

Under Virginia Code § 46.2-942, when someone is tried for exceeding a speed limit, the court must receive a sworn report of a calibration test of the speedometer in the vehicle the defendant or the arresting officer was driving, and must consider it in deciding both guilt and punishment. That doesn’t make a faulty speedometer a defense. In Williams v. Commonwealth, 5 Va. App. 514 (1988), the Court of Appeals of Virginia held that an inaccurate speedometer does not bar a conviction and that the statute does not make knowing your speed an element of the offense. The question is whether the car was in fact going faster than the law allows, and the fact finder decides how much weight the report deserves. The court also recognized that the report is relevant to punishment.

Williams involved an ordinary speeding charge under an earlier version of the statute, but its reasoning applies to the speed element of reckless driving by speed. The same statute applies to an ordinary speeding ticket. An error in your own speedometer doesn’t change the speed the officer measured. In practice, a favorable calibration works as mitigation: it can matter when a prosecutor considers a reduction and when a judge decides the sentence.

Two practical points follow. The report should be sworn, so ask the shop for a signed, notarized report rather than a printout. And § 46.2-942 sets no deadline for the test, unlike the six-month validity limit that § 46.2-882 places on radar and lidar calibration. A test done long after the stop, or after the tires or wheels have changed, may carry less weight.

When a calibration can help

It is most useful when three things line up: the alleged speed sits near the reckless driving threshold of 20 mph or more over the limit, or more than 85 mph; your speedometer reads low at about that speed; and the car hasn’t changed since the stop. For example, if radar put you at 80 in a 60 and your speedometer shows 76 when the car is actually going 80, the report supports what you may already believe: that you thought you were under the line. A prosecutor may weigh that in considering a reduction, and a judge may weigh it at sentencing. It does not show that the radar was wrong. If you aren’t sure your summons charges reckless driving rather than speeding, our comparison of the two explains how to tell.

A calibration can also matter in a pacing case, where the officer followed your car and estimated your speed from the patrol car’s speedometer. There, the accuracy of the officer’s speedometer is part of the Commonwealth’s proof, and § 46.2-942 covers that vehicle too. We ask whether the patrol car’s speedometer was tested and when. Our guide to radar, lidar and pacing evidence explains how each method is checked.

At very high speeds, a reduction may not be realistic. A report showing a low-reading speedometer can still be part of what a judge weighs in deciding the sentence.

What a calibration can’t do

A speedometer that reads accurately adds little, and one that reads high can hurt, because it suggests you saw a number even higher than the speed charged. A calibration can also confirm the officer’s reading. In Williams, the driver’s own test showed his speedometer read 45 mph when the truck was actually going 58, which supported the radar instead of helping him. New tires, a different wheel size or work on the instrument cluster can change the reading, so a test after those changes may not reflect the car as it was on the day of the stop.

In a radar or lidar case, the more direct challenge, when one exists, is usually to the officer’s device: whether its calibration records are present, whether they cover the date of your stop, and whether the reading belongs to your car. That is a separate question from your own speedometer. Our firm has had reckless driving charges dismissed where the device’s calibration was dated after the offense or fell outside the six-month period and there was no adequate independent proof of accuracy. A missing or defective certificate doesn’t guarantee dismissal, because the Commonwealth may offer other admissible evidence.

Results depend on the facts and circumstances of each case. Past outcomes do not guarantee future results.

A calibration is a tool counsel uses alongside the rest of the case; we decide with you whether it’s worth getting.

When to get one, and what to ask for

Before recommending a test, we ask about the car, its tires and any recent work, the speed alleged and how it was measured. On a lower speed or a newer car, we may not recommend one.

If we recommend a calibration, arrange it promptly, before any tire, wheel or dashboard work, and keep a record of any changes to the car since the stop. In Northern Virginia, a calibration typically costs $100 to $150. Many drivers here use M&M Collision in Fairfax, a shop that many local defense lawyers recommend. Call ahead to schedule, bring a copy of your summons, and keep the receipt.

Ask the shop for a sworn report that identifies the vehicle by VIN, gives the date and odometer reading of the test, names the shop and technician, and lists the results at several speeds, including speeds close to the one on your summons. Bring the report to your lawyer rather than handing it to the officer or prosecutor yourself, so we can decide whether and how to use it.

A calibration is one part of preparing for court. We’ll tell you what else is worth doing before your court date, such as reviewing your driving record or completing a course.

Frequently Asked Questions

Talk with NOVADefenders before you schedule the test

NOVADefenders, S&R Law Firm PLLC represents drivers charged with reckless driving in Northern Virginia from our office across the street from the Fairfax County courthouse. Call 703.273.6431 for a free consultation or contact us online. Tell us the speed and limit on your summons, how the officer measured it, and whether anything about your car has changed since the stop.

Reviewed by attorney Ryan Rambudhan | Updated October 6, 2026