Why alcohol impairs driving

The validity of using the driving simulator for the study has been researched in depth by Bella [ 22 , 23 ]. Driving simulations were performed with the AutoSim driving simulator system. The simulator consists of six network computers and some operation hardware interfaces, including steering wheel, three pedals, and manual gearshift.

The road scenario is projected onto three big screens in front providing a degree field of view, with two rearview mirrors on each side and one screen on the back. The width of the vehicle was about 1. The simulator can record the degree of the actions of the driver stepping on three pedals brake, throttle, and clutch , the steering wheel angle, and the gear state.

The driving simulator was shown in Figure 1. The detector is the same type as the one used by traffic police in Beijing. The BAC level of participants was measured five times each testing and the mean BAC level was used to minimize measurement errors. The scenario was designed as four-lane bidirectional urban road, including 5 urban straight roadway segments and 6 urban curves. The width of the road lane was 3. The straight roadway and curve were alternant in the scenario.

Each urban straight roadway segment was meters long. Considering that driver would accelerate or decelerate, we considered the middle meters an urban straight roadway segment, which was the object of study. To avoid the interference of other vehicles, the scenario was designed without any other vehicles. Then participants can drive freely in the road. The designed scenario was shown in Figure 2. To analyze the effect of alcohol on driving performance at different level, participants were required to conduct experiments at three different BAC levels.

The low BAC level was set around 0. The high BAC level was set higher than 0. The BAC level of 0. Another driving state was the normal state, which was considered the control state. According to the driving state design, each participant performed the simulated driving experiment four times in four different days. To avoid residual effects of alcohol dose, the participants carried out the experiments at four BAC levels of 0.

Generally, TBW for men is as follows:. With each drink, the dose was first calculated according to the equations above for each subject. When they achieved the target BAC levels, the simulated driving began. The procedure of the four times experiments was shown in Table 1. Each participant was asked to perform the four visits with a random order to balance the effect of the order on drivers.

All the participants were required to sleep well at least three days before experiments and refrain from having any stimulating food or beverage. They were also asked to have a noon break at least one hour on the day of the experiment. At the beginning of the experiment, participants had to meet the requirements of normal state to get experiment data without interference of other states.

In the first time experiment, subjects were instructed regarding the operation of the simulator, the experimental procedure, and the tasks to be performed. Then, they were given approximately 10 minutes to practice driving to familiarize themselves with the simulator control and the road environment. In each time, subjects were invested about their state before simulated driving experiment to ensure that they were not affected by any other unexpected factors. They were asked to have a break about 5—10 minutes in middle of simulated driving process to avoid fatigue.

Each subject drove in two random scenarios and therefore had 10 urban straight roadway segments data. After simulated driving, participants were required to fill in the questionnaire, which included attitude, vigilance, attention, judgment, reaction, and ability of controlling vehicle. The two parameters were considered the representative of driving performance.

Lane position was defined as the distance between the center of the vehicle and the lane line on the right. Considering that the width of road lane was 3. At the same time, all the subjects completed successfully the questionnaire and the data were collected integrally. Participants were investigated after drinking driving with BAC level of 0.

They were required to fill out the questionnaire contrasting with their feelings when normal driving. Each aspect of the investigation included three options, which meant worse, invariant, and better, respectively, contrast with normal driving. For example, the three options for safety attitude were adventurous, invariant, and cautious.

The objective of the analysis was to explore the signatures of alcohol impairment. The data was analyzed according to the following method. The indicator value of each participant was the mean of all his driving sections excluding accident sections.

ANOVA with repeated measures was used to analyze the differences of each indicator at the four states. The pairwise comparison was analyzed using post hoc -test.

Firstly, all the drinking driving states at different BAC levels were put in one group to identify normal driving state without considering different BAC levels; then, drinking driving states with different BAC levels were separately distinguished from normal driving state.

Compared with normal state, drivers described their feelings under the influence of alcohol after drinking simulation driving.

The distribution of the investigation results for 25 subjects was shown in Figure 3. The driving attitude and safety attitude showed driving tendencies of drivers. It indicated that most subjects admitted that they had the tendency of sensation-seeking and were more adventurous under the influence of alcohol. It was revealed in Figure 3 that all of the abilities on perception, attention, direction-sense, judgment, controlling, and reaction of most drivers were impaired by alcohol.

More than half of subjects felt that the vehicle moved slowly, which might make them drive much faster. Each participant drove 10 straight roadway segments and each section was meters long.

There were some accidents in their simulated driving process. Some drivers rush out or drove into the guardrail in center of the road. At different driving states, we defined accident rate that the ratio of the total number of the segments including accidents of all participants divided the total number of urban straight roadway segments of all participants had driven. The accident rate at different states was shown in Table 2. The accident rate 1. Table 2 showed that the higher BAC level induced higher accident rate, which indicated that driving ability was impaired more seriously at higher BAC level.

Driving performance data was analyzed to reveal the effect characteristics of drunk driving on running vehicle. The means of all subjects of each indicator at different driving states were shown in Figure 4.

The main differences between normal driving and drinking driving were analyzed with ANOVA method firstly. The quadratic trend was not significant. There was no significant difference among the three BAC levels. Of the within-subjects effects, the main effect of BAC was also statistically significant, , , and partial. Based on the width of road lane, the best value of lane position was 1. Figure 4 c showed that drivers when normal driving had a left driving tendency than center of lane, but with right tendency than center of lane when drinking driving.

The main effect of BAC of the within-subjects effects was statistically significant, , , and partial. There was no significant difference in other comparisons. The results of the ANOVA analysis above showed that there are no significant differences of indicators at different BAC levels of drinking driving states. But significant differences were found for some indicators between normal state and drinking driving states.

It was indicated that the indicators in urban straight roadway segment might support the discrimination of two states: normal and drinking driving, but they were difficult to support the classification of different BAC levels.

To explore the discriminant ability of the driving performance indicators, firstly, the data at the three BAC levels were integrated into one group to distinguish normal state; then, drinking driving states at the three BAC levels were considered one group, respectively, to identify normal state.

Therefore, four different discriminant functions were established based on the significant indicators. It was confirmed that each indicator in the drinking driving states and normal states was significantly different. The data met the conditions of using Fisher discriminant method based on the statistical results. For the discriminant of drinking driving states including all BAC levels and normal states, the standardized discriminant function is where is the discriminant score and means the standardized indicator.

Drinking reduces your attention span and prevents you from concentrating on the road. In addition, you have to concentrate on other drivers and their unpredictable actions. Impaired vision. As you consume alcohol, your vision is negatively affected.

Some people experience blurred or double vision or an inability to control eye movement — these effects usually occur with excessive drinking and create a dangerous situation if you choose to drive.

Lack of coordination. Motor skill function becomes increasingly more difficult the more alcohol you drink. You will begin to notice some of these effects with your first drink. If you even question your ability to drive, put down your keys and find a ride. For more information about an Intoxalock ignition interlock device, call our state specialists at Know the facts about what each subsequent drink does to your ability to operate a vehicle safely.

Fortunately, the children and staff were unharmed. But just minutes before, my son and I had walked through the exact spot in the building where the truck came to rest in a pile of debris. My frightening brush with a drunk driver made me wonder about what practices and policies could help prevent such accidents and fatalities — and question yet again whether motorists are fully aware of the importance of responsible consumption before getting behind the wheel.

Drunk drivers often express surprise, disbelief or denial about their blood alcohol concentration BAC or level of impairment when they arrive in the ER. And the more you drink, the harder it is to judge how intoxicated you are. Studies have shown that increasing BAC is also associated with a decreased reaction time. One study pointed to an average decreased reaction time of milliseconds — just over a tenth of a second — associated with a BAC level of 0.

So, when cruising at 70 miles per hour, a drunk driver would travel for an additional 12 feet before reacting to a roadway hazard. It might not take as many drinks as you think to slow your reaction time and make safe driving harder.

To account for an individual imbibing over a longer period of time, subtract about 0. A pound man that consumes two alcoholic beverages will experience some loss of judgment, decreased ability to rapidly track a moving target and reduced multitasking ability, according to the Centers for Disease Control and Prevention.