Final answer:
Alcohol and/or drugs affect both alertness and concentration, as well as reaction time and coordination, all of which are critical for safe driving. Field Sobriety Tests evaluate these impairments to identify intoxicated drivers.
Step-by-step explanation:
The use of alcohol and/or drugs can significantly impair a variety of driving skills. These substances affect alertness and concentration, which are crucial for noticing and responding to road conditions and traffic signals. Moreover, alcohol and drugs also slow reaction time and weaken coordination, making it more difficult to control the vehicle and respond to emergencies. Field Sobriety Tests (FST) often assess these skills to determine if a driver is under the influence. In addition to these immediate effects, chronic exposure to alcohol can lead to addiction, tolerance, and withdrawal effects that further deteriorate driving abilities.