Abstract
An earlier study by the Bureau of Motor Carrier Safety for assessing the effect on drivers of prolonged driving, rest breaks, different types of operation and other situations, was the measurement of heart rate and variation in heart rate. Even if this BMCS study had been able to demonstrate a relationship between changes in heart rate and driving time, it failed to consider a large number of variables that may have influenced the results obtained. This indicates a possible cursory understanding of cardiovascular physiology.