Vehicle-type and Lane-Specific Free Speed Distributions on Motorways

We present a new approach to estimate vehicle-type specific free speed distributions on multilane facilities based on the concept of censored observations. The original distribution-free method of Kaplan-Meier is generalized to include partially censored data, i.e. observations that are censored with a certain probability or 'to a certain degree'. The method is applied using cross-section data collected at a busy two-lane motorway in the Netherlands. The results provide robust estimations of the speed distribution for the different vehicle classes, while removing the structural error made when applying more common approaches. Word count Abstract: 90 Main text: 4600 Tables (3) 750 Figures (7) 1250 Total: 6690