Operational Analyses of Freeway Off-Ramp Bottlenecks

The paper presents the findings to date of operational analyses at freeway off-ramps with emphasis on analysis procedures on recurrent off-ramp bottleneck locations at the Attiki odos motorway (Attica Tollway) in Athens, Greece. We compared the observed traffic performance metrics at two sites with the predicted measures using the methodology of freeway diverge areas and weaving sections in the 2010 edition of Highway Capacity Manual (HCM) for a wide range of traffic conditions. The findings indicate that the HCM volume predictions at the diverge area are in close agreement with field data and the density is underestimated by 7% on the average. The HCM weaving analysis methodology underestimated the weaving section capacity especially for high weaving volumes, and overestimated the section density by 17% on the average.