Which substance has the most significant effect on a driver's reaction time?

Drinking alcohol has the most significant effect on a driver's reaction time because it impairs cognitive functions and motor skills. When consumed, alcohol affects the central nervous system, leading to slowed processing speed, decreased coordination, and impaired judgment. This reduced ability to react quickly to unexpected situations on the road is critical since driving requires rapid responses to changing conditions.

Alcohol can alter perception, making it more difficult for a driver to assess distances and speeds accurately, which is essential for safe driving. Even small amounts of alcohol can have measurable effects on reaction time, increasing the risk of accidents. Therefore, understanding the impact of alcohol is vital for promoting safety on the roads and making informed decisions about driving after drinking.