An Inside Look at Field Sobriety Tests: Ensuring Road Safety


When it comes to road safety, one of the prevalent issues is impaired driving due to alcohol or drug intoxication. Law enforcement officers utilize specialized testing methods to detect such situations, primarily through Field Sobriety Tests (FST). The tests help reduce incidents of Driving Under the Influence (DUI) considerably, thus ensuring the safety of all road users.

What is a Field Sobriety Test?

Field Sobriety Tests are precisely what the name depicts – a series of tests conducted in the field (usually on the roadside) that allows law enforcement to assess whether a driver is impaired by alcohol or drugs. These tests are often used in conjunction with other impaired driving tests like breathalyzer tests and blood tests to ascertain a driver’s sobriety level. The field sobriety tests vary in form, but the primary goal is to evaluate a driver’s physical and cognitive capabilities, which could be hindered due to intoxication.

You can learn more about it in our DWI Start to Finish blog post.

The Four Tests of a Sobriety Checkpoint Procedure

Now that we understand what a Field Sobriety Test entails, let’s review the four main tests officers conduct during these Field Sobriety Exercises. Each test is designed to evaluate different indicators of impairment and provide sufficient evidence for a DUI arrest.

The Breathalyzer Test: Detecting Blood Alcohol Content

The Breathalyzer Test is a widely known and commonly used tool for DUI enforcement. This test requires the suspect to blow into a device that measures the Blood Alcohol Content(BAC) present in their breath. The legal BAC limit in Texas, as covered in our What is a DWI in Texas blog post, is .08, and exceeding this limit can lead to a DUI arrest.

The Horizontal Gaze Nystagmus Test: Evaluating Eye Movements

The Horizontal Gaze Nystagmus (HGN) test involves an officer moving an object, such as a pen or a small flashlight, horizontally in front of the suspect’s eyes. The officer would observe the suspect’s eye movements, looking for ‘nystagmus’- an involuntary jerking of the eye as it gauges from left to right. We have covered these involuntary jerks and their cause in our Guide to DWI Laws and Penalties blog post.

The Walk and Turn Test: Assessing Balance and Coordination

In the Walk and Turn test, the officer instructs the suspect to take nine heel-to-toe steps along a straight line, turn around on one foot, and return in the same manner. This test assesses the individual’s balance, coordination, and ability to follow instruction, each of which could be affected by alcohol impairment.

The One Leg Stand Test: Evaluating Physical and Mental Impairment

In the One Leg Stand test, evaluated through NHTSA’s guidelines on sobriety tests, the suspect is asked to stand on one foot while counting aloud until told to stop. This test helps assess the suspect’s balance, coordination, and ability to perform tasks requiring divided attention.

Incorporating these tests into DUI enforcement not only aids in apprehending impaired drivers but also serves as a deterrent to those considering drinking and driving. Check out the CDC’s report on impaired driving for statistical data on how such tests have contributed to decreasing DUI incidents. For safe driving tips, visit AAA’s Tools and tips to avoid drunk driving.

Building awareness of these tests and understanding their importance can go a long way in curbing the incidence of drunk driving and, thereby, making our roads safer. Whether you’re a driver or a passenger, awareness of these tests and their role in traffic safety can play a significant role in promoting road safety.

Comparing DUI Testing Methods with Standardized Sobriety Tests

Different DUI testing methods and Standardized Sobriety Tests each play a crucial role in DUI enforcement, though they vary in process and utility. While DUI tests such as breathalyzer tests and blood tests primarily focus on quantifying the amount of alcohol through Blood Alcohol Content (BAC), sobriety tests have a different focus. As discussed in our Field Sobriety Tests blog post, they examine physical and cognitive impairment signs directly. This approach offers a real-time assessment of a suspect, enabling law enforcement officers to note behavioral clues of impairment—an aspect often omitted in other DUI testing methods.

Understanding the DUI Arrest Process

The DUI arrest process may vary slightly by locale but typically follows a standard format echoing the principles covered in our blog post: What Happens When You Get a DUI. Once an officer suspects a driver of DUI, they’ll conduct a field sobriety test followed, usually, by a breathalyzer test. If the officer deems the driver impaired beyond the legal limit, the arrest is made. Sobriety checkpoint procedures play a significant role here, enabling officers to stop and assess drivers at specific locations, preventing potential drunk drivers from hitting the road.

Assessing The Effectiveness of Sobriety Tests

Road safety continues to be a pressing concern across the globe, and sobriety tests like those mentioned in our Steps to Win Against DUI Charge article, play a significant role in preventing DUI incidents. These tests are designed to screen drivers for impairment promptly and effectively. Some might argue the subjectivity involved in such tests, but, backed by NHTSA’s guidelines, the tests have shown effectiveness in identifying and reducing impaired driving.


The importance of understanding sobriety tests cannot be understated. Designed to evaluate impairment, these tests are valuable tools in DUI enforcement, enhancing road safety. They form a major part of DUI arrest processes, with the goal of minimizing drunk driving incidents. However, their roles complement other DUI testing methods, offering a more holistic approach to detecting and preventing DUI. By understanding these tests, we can appreciate the efforts law enforcement undertakes to preserve our safety on the roads.

Don’t stay in the dark about DUI enforcement and the role of sobriety tests in safeguarding road safety. Contact us now to have your questions on this topic answered by our experts. Also, call us now to speak directly with our team, and don’t forget to visit our blog for more educational and insightful content.

Field Sobriety Tests - Frequently Asked Questions (FAQ)

The four primary tests conducted during a sobriety test are:

  • The Breathalyzer Test: Measures the Blood Alcohol Content (BAC) from a breath sample.
  • The Horizontal Gaze Nystagmus Test: Evaluates the eye movement for signs of impairment.
  • The Walk and Turn Test: Assesses balance and coordination.
  • The One Leg Stand Test: Evaluates physical and mental capabilities.

The breathalyzer test involves the test subject blowing into the device, which measures the Blood Alcohol Content (BAC) from their breath sample. If the BAC is greater than the legal limit (typically 0.08%), it may indicate the subject is under the influence of alcohol.

While there’s ongoing debate about the exact accuracy percentage, field sobriety tests are generally considered effective tools when properly conducted. They are particularly useful for officers in making real-time assessments of suspected impairment.

In most jurisdictions, you can technically refuse Field Sobriety Tests but refusal could lead to penalties such as immediate driver’s license suspension, based on “implied consent” laws. You should consult your local and state regulations or a lawyer for specific advice.

Sobriety tests play a crucial role in identifying and preventing drunk driving. They allow law enforcement to screen drivers for alcohol or drug impairment, thus reducing the risk of accidents caused by impaired driving, and making the roads safer for everyone.