Texas Personal Injury Law Blog

The Five Kinds of Driving Impairment

Wind gusts and lightning strikes cause a few Harris County vehicle collisions every year. But most car crashes are not “accidents.” In fact, human error is directly or indirectly responsible for over 90 percent of these incidents. Driving impairment is often a major factor in these.  The National Highway Traffic Safety Administration has identified five types of driving impairment, as outlined below.

Medical Condition

Many Houstonians deal with chronic medical conditions which could cause sudden and unexpected loss of consciousness. Some of these conditions include:

  • TIA (Transient Ischemic Attacks), or mini-strokes,
  • Epilepsy,
  • Heart disease, and
  • Diabetes.

People with these conditions are often ineligible for drivers’ licenses due to the risks. So, if they drive, experience a medical episode, and cause a crash, they could be liable for damages as a matter of law. Even if the tortfeasor (negligent driver) had a valid license, driving with a known dangerous medical condition after a doctor advises against it clearly demonstrates a lack of ordinary care.


Although hand-held cell phones are just one component of the distracted driving crisis, these gadgets get most of the attention. They combine all three forms of distracted driving, which are:

  • Cognitive (taking one’s mind off driving),
  • Visual (taking one’s eyes off the road), and
  • Manual (taking at least one hand off the wheel).

Other sources of distracted driving include using a hands-free cell phone (these gadgets are cognitively and visually distracting), eating while driving, and talking to passengers while driving.


driver impairmentThe next three forms of driving impairment are all closely related. Alcohol causes about a third of the fatal car accidents in Houston. This substance clouds judgement and impairs motor skills. Legal intoxication requires a blood alcohol level of .08, however, this does not mean that driving is not impaired at lower levels. Even one drink may affect someone’s motor skills and/or reaction time resulted in an alcohol-impaired driver getting behind the wheel.

Injured victims may use both direct and circumstantial evidence to establish liability in these cases. If the tortfeasor was arrested for DUI, the conviction is admissible to show negligence. In other cases, victim/plaintiffs may use circumstantial evidence of alcohol consumption, like bloodshot eyes and erratic driving to prove negligence.


In many areas, there are more “drugged drivers” than “drunk drivers.” Typically, the substance is one of the following:

  • Street drugs like heroin and cocaine,
  • Prescription drugs like Xanax and Oxycontin, or
  • Over-the-counter drugs like NyQuil and Sominex.

These substances have a similar ability to impair a driver as alcohol. Further, while it may be legal to take prescription and over-the-counter drugs, it is often illegal and dangerous to drive while under their influence.

The same liability theories outlined above with regard to alcohol are applicable here. In Texas, any substance, including alcohol, can support a DUI charge if it causes the driver to lose the normal use of his or her physical faculties. Furthermore, driving under the influence of drugs is an extremely dangerous type of driving impairment.


Drowsiness and alcohol affect the brain in about the same way. Driving after eighteen consecutive awake hours is like driving with a .05 BAC. That’s a very dangerous level of impairment. Furthermore, those old tricks that tired drivers use, like turning up the radio and drinking coffee, usually do not work. Just like only time can cure alcohol or drug impairment, only rest can cure fatigue.

Since there is no Breathalyzer test for fatigue, victim/plaintiffs must always use circumstantial evidence to establish liability. Erratic driving at certain times of day or night is usually the best evidence, along with statements from the tortfeasor about being tired.

Lawyers for Accidents Caused By Impaired Drivers

Impaired drivers often cause serious injuries. You need an aggressive car accident lawyer on your side.  We’ve handled thousands of car accidents in Texas including numerous accidents caused by impaired drivers. For a free consultation with our experienced accident attorneys, contact Simmons & Fletcher, P.C.

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Paul Cannon

Paul Cannon has practiced personal injury trial law since 1995. He is Board Certified in Personal Injury Trial Law (2005). He has earned recognition as a Super Lawyer by Thompson Reuters in 2017 & 2018, and as a Top 100 Trial Lawyer by the National Trial Lawyers Association in 2017. He is a Shareholder, trial lawyer and online marketing manager at Simmons and Fletcher, P.C. His legal writings have been published by the Texas Bar Journal, Business.com, Lawyer.com HG Legal Resources, Lawfirms.com, and others. He has been asked to give education talks and media interviews on dog bite law.