PROCEDURES TO DETERMINE DESIGN-HOUR VOLUME BY PREDICTING A RANKED HOURLY VOLUME DISTRIBUTION

The conventional procedures used to determine highway sizing are normally based on the identification of design-hour volume, which is commonly the 30th highest hourly volume (HHV), and the assumption that the K-factor (the ratio of the 30th HHV to the annual average daily traffic (AADT)) remains constant over time. This paper presents a method to predict directly a ranked hourly volume distribution (RHVD) by combining a ranked daily volume distribution and a distribution of ranked hourly coefficients (average hourly volume expressed as a percentage of the AADT). Then, design-hour volume will be determined as the 30th HHV of the estimated RHVD. The analysis and estimation of RHVD also reveal a causal reason why a knee of curve occurs in the region at or near the 30th HHV, and why the K-factor actually decreases over time.