What does the 50th percentile speed represent?

• A. Mean speed of observed data set
• B. Median speed of observed data set
• C. Highest recorded speed
• D. Speed limit recommendation

Answer: (B)

The 50th percentile speed is defined as the median speed of the observed data set. In statistical terms, the median is the value that separates the highest half from the lowest half of the data. When the speeds of vehicles are arranged in ascending order, the 50th percentile represents the speed at which half of the observations fall below this value and half are above it. This measure is particularly useful in transportation because it provides a more robust indicator of typical travel speeds than the mean, especially in datasets with outliers or skewed distributions. It reflects the speed at which a majority of drivers are traveling, making it a valuable statistic for roadway design and traffic engineering to ensure safety and efficiency on the roads.