The rise of trucks and the fall of throughput

This paper collects data from the morning peak period of 564 loop detector stations across the Minneapolis–St. Paul freeway network for all workdays from 1995 to 2019. Saturated stations that meet different saturation levels are identified using fundamental diagrams (FDs) to assess the change in throughput of every link on the network over 25 years. The average network throughput decreases from approximately 1850 vehicles per lane per hour in 1995 to about 1600 vehicles per lane per hour in 2019. The critical density drops from approximately 24 vehicles per lane per kilometer in 1995 to about 19 vehicles per lane per kilometer in 2019. During this period, the number of trucks increased by 153.71% overall, ranging from SUVs (1043.62%) and tractor trailers (128.94%). After conducting Granger-causality tests on motor vehicle types and traffic levels across the freeway network and at permanent classification stations, our findings corroborate the hypothesis that the increase in the share of trucks causes a decrease in throughput. © 2025 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.