Author: Sasha Tanner
How much does speeding factor into crashes caused by impaired drivers? Johnson (2025) sought to quantify this age-old question in a study that analyzed the relationship between speeding, alcohol impaired driving, and crash risk.
Study Design
Data
The researcher collected alcohol-related crash data among 5,138 cases obtained from NHTSA’s 2019-2021 dataset, which included the following information:
- Measure of vehicle speed just (about 4.5 seconds) before the crash
- Driver characteristics
- Demographics (age, sex, race, etc.)
- Injury severity (ranges from no injury at all to death)
- Blood-alcohol concentration (BAC) levels of the driver
- Extent of property damage
Models
Additionally, Johnson (2025) employed 3 analytic models to better understand the relationship between alcohol, speeding, and crash risk:
- Observe data with and without BAC input to identify any distinctions
- Observe vehicle speed in relation to demographic characteristics, injury severity, and BAC levels
- Assess crash risk in relation to speed and BAC levels
These models were measured by individual formulas. First, he measured the relative odds (i.e., risk) of crash involvement indicated by vehicle speed changes. He then used another formula that measured the risk of crashes at different BAC levels. The last formula did not measure speed at all, controlling for demographics and whether the driver was under the influence of drugs and/or alcohol.
Results
Model 1: Drivers with no recorded BAC level were at a lower speed just before the crash compared to drivers with recorded BAC levels.
Model 2: Crash cases without alcohol influence were characterized by decreased speed levels in the same locations where alcohol-induced, higher speed crashes occurred.
- For drivers with less severe injuries, BAC did not affect speed levels.
- However, drivers who had extreme injuries, died, and higher BAC levels had driven at faster speeds.
Model 3: Half of the fatal crash cases where the driver had a BAC of 0.08 g/dl is associated with higher speed levels.
- Minor injuries were characterized by similar, yet lower speed levels across three BAC levels (0.00, 0.08, and 0.16 g/dl). This means that driving at a lower speed, sober or not, is linked to less severe injuries.
- Serious to fatal injuries were characterized by higher speed levels across three BAC levels (0.00, 0.08, and 0.16 g/dl). This means that driving at a higher speed is linked to higher BAC levels, which result in more severe injuries.
- A BAC level of 0.08 g/dl increases the risk for serious injuries
- Every other case can be explained by higher speed levels.
Technology and Data Recommendations
Since speed and alcohol impaired driving are heavily linked, it’s critical to develop and implement technology that detects intoxication and controls speed levels in automatic response into new vehicle models.
Moreover, there are limitations in randomized data about alcohol-impaired driving cases. Non-fatal crashes were only collected if the person was hospitalized; the vehicle was towed, or the officer suspected alcohol influence. As a response, all crash data, regardless of low to high severity, should be collected to provide a more complete picture of the problem.
Speeding and alcohol-impaired driving are more related than you think. Check out the article below to get the details.
Source: Johnson, M. B. (2025). Drunk driving has a speeding problem. Traffic Injury Prevention, 26(7), 755–759. https://doi.org/10.1080/15389588.2025.2456942
