Regional and Area-Type Modeling of Peak Spreading on Connecticut Freeways

Predicting accurate peak-hour traffic volumes has become increasingly important; these volumes are being used for quantitative analysis; for determining benefits of highway improvements; and for estimating pollutant emission levels. A traditional, and commonly used, procedure predicts the daily traffic demand for all network links and converts these volumes to peak-hour quantities, using “K” factors. The accuracy at the link level is highly questionable, because these factors do not capture the variability in link characteristics that might influence the peak-hour factors. This paper describes a recently completed study of peak spreading at 10 freeway locations in Connecticut. The study considered congestion, region, and area type for predicting the proportion of the four-hour, peak-period volume on a highway link concentrated in the highest hour during the period. This effort is intended to enhance the existing traditional four-step transportation planning procedure. Linear regression relates the congestion measure and link-related variables to the peak-hour proportion. The research findings are presented, along with a discussion of ongoing research activities.