Overview Summary
- Some agencies in the U.S. and Canada are reconsidering or discontinuing tuning fork tests, raising questions about RADAR accuracy verification and courtroom defensibility.
- Internal self-tests and speedometer checks alone do not evaluate the entire RADAR signal path or verify accuracy to the required ±1 MPH tolerance.
- Only a calibrated tuning fork test provides an external reference that validates the full RADAR system, including the antenna.
- Long-standing legal precedent continues to support tuning fork tests as part of an accepted accuracy-validation process.
- Eliminating tuning fork tests can introduce risk by weakening evidentiary foundations and increasing challenges in court.
- A layered accuracy approach, combining internal self-tests, speedometer comparison, tuning fork tests, and laboratory certification, remains best practice.
- The Eagle 3’s Electronic Tuning Fork Test makes fork testing fast, consistent, and easy to document without slowing operations.
As RADAR technology continues to evolve, some agencies are re-evaluating long-standing equipment performance and functional test standards, particularly the use of tuning forks. In recent years, some agencies have discontinued tuning fork tests entirely. This trend has introduced new questions: Are tuning fork tests still truly needed? Should agencies consider phasing them out?
In this updated review, we break down why fork tests still matter, how legal precedent continues to support them, and why modern RADAR systems, particularly the Eagle 3, keep the process fast, precise, and minimally disruptive to operations.
Why Tuning Fork Tests Still Matter
Recent industry discussion has questioned whether tuning fork tests are still needed, and some agencies have already removed them from their daily test procedures. However, the technical and legal foundations for tuning fork tests remain unchanged, and eliminating this step creates significant gaps in a RADAR program’s accuracy verification process and increases the agency’s risk.
Modern RADAR units perform automatic internal self-tests using two independent quartz crystal time bases. These internal tests are valuable because they ensure the Doppler calculation time base is functioning properly. However, no manufacturer’s RADAR system includes an internal self-test that evaluates the entire signal path. Internal test signals do not pass through the microwave antenna, which means a unit could pass an internal test even if the microwave receiver has failed.
It is recommended that officers compare the RADAR patrol speed reading to the patrol vehicle’s speedometer several times during a shift. While this method is a good external reference to support the RADAR internal self test because the Doppler shift travels through the entire signal path, it is limited by the accuracy of the vehicle’s speedometer, which cannot verify the RADAR to the required ±1 MPH tolerance.
This is where the tuning fork test becomes indispensable. A certified tuning fork provides an external test frequency reference that:
- Sends an external signal through the entire RADAR system—including the microwave receiver
- Verifies the unit’s accuracy to the required ±1 MPH tolerance
- Completes the testing path started by the internal self-test and speedometer comparison
- Confirms the RADAR is functioning properly at both the beginning and end of each shift
Tuning fork tests have also been part of accepted legal standards for decades, with case law recognition dating back to State v. Tomanelli (1966). For many agencies, removing tuning fork tests risks weakening courtroom defensibility, reducing transparency, and relying solely on diagnostics that cannot detect certain system-level failures.
Why Removing Tuning Fork Tests Introduces Risk
While removing tuning fork procedures from RADAR policies may appear to streamline operations, doing so introduces measurable risks to accuracy, consistency, and courtroom defensibility. Without an independent external verification, the integrity of RADAR readings becomes easier to challenge.
Eliminating tuning fork tests can:
- Reduce evidentiary strength in court.
- Create inconsistencies between statewide and local standards.
- Encourage reliance on internal tests alone, which are not full-system validation.
- Lead procurement teams to assume fork testing no longer adds value.
Courts often view the absence of a tuning fork test as a gap in an agency’s accuracy-validation process, regardless of internal self-tests or diagnostics. This risk increases when a traffic stop leads to additional enforcement action. If the original stop is invalidated due to questionable RADAR accuracy, the probable cause for subsequent actions may also be compromised.
For agencies committed to consistent, defensible, and transparent enforcement practices, tuning fork tests remain a best-practice functional performance check.
Recommended Approach for RADAR Accuracy
To ensure RADAR readings are accurate, defensible, and compliant with agency and state standards, we recommend the following four-step process:
- Perform the tuning fork test as outlined in the operator manual.
- Conduct internal self-tests according to agency policy and manufacturer recommendations.
- Compare the RADAR patrol speed reading against the patrol vehicle’s certified speedometer.
- Schedule periodic laboratory certification as required by state law or department policy.
This layered approach remains the most effective way to guarantee full-system accuracy, ensuring an evidentiary foundation and that the RADAR equipment is court-ready.
Kustom Signals Has Products That Support Fork Testing… And Make It Easier
TKustom Signals continues to recommend performing tuning fork tests as outlined in our product operator manuals. Tuning fork tests help agencies:
- Confirm accuracy at the start and end of the officer’s shift.
- Validate the entire RADAR system, not just internal components.
- Meet long-standing legal and evidentiary standards.
- Strengthen officer credibility in testimony and reporting.
We support tuning-fork accuracy verification across our RADAR lineup, including:
Each system is designed to work with tuning forks as specified in the operator manual, ensuring complete validation before and after enforcement activities.
Eagle 3 Makes Fork Testing Fast, Easy, and Highly Reliable
Traditional fork tests require officers to strike the tuning fork and position it properly. The Eagle 3 Electronic Tuning Fork test, however, streamlines and automates much of this process.
The Eagle 3:
- Completes a comprehensive fork test on two antennas in less than 20 seconds.
- Eliminates the need for repeated manual fork strikes.
- Displays measured fork values and calculated results instantly.
- Reduces opportunities for user error.
- Provides an automatic test log that enhances documentation and confidence.
This design removes the traditional burdens of fork testing, including time, technique, and variability, while preserving the accuracy and defensibility agencies rely on.
Watch the following video for a time comparison of Eagle 3’s electronic fork versus a traditional fork test:
“The Advanced Tuning Fork Test eliminates the need to perform multiple separate fork tests for stationary and moving operations with a one or two-antenna RADAR system. The operator simply rings the low and high fork once for each antenna. The RADAR clearly displays the measured fork values and calculated results greatly reducing the time an officer may spend each day conducting fork tests without losing the accuracy or confidence of a traditional fork test,” says Kent Hayes, Kustom Signals Speed Product Manager.
Leave Nothing to Chance with Kustom Signals
Even as some states discontinue tuning fork tests, the practice remains one of the most reliable and court-supported methods of confirming RADAR accuracy. Until national standards formally change, tuning fork tests are still essential for transparent, defensible, and credible traffic enforcement.
With the Eagle 3’s streamlined eFork Test, agencies can preserve the integrity of their accuracy protocols while minimizing time and effort. Accuracy and efficiency do not need to be in conflict. In fact, with the Eagle 3, they align.
To learn more about RADAR accuracy validation or the Eagle 3’s Advanced eFork Test, please contact Kustom Signals.