Citation

Luttinen R. Transp. Res. Circular 2000; (E-C018): 175-187.

Copyright

(Copyright © 2000, U.S. National Academy of Sciences Transportation Research Board)

DOI

unavailable

PMID

unavailable

Abstract

Traffic flow data have been collected from 20 automatic traffic recorders on Finnish two-lane highways. Observations were aggregated in 15-minute time intervals plus an optional one-minute extension period using a doubly synchronous counting process. Refined passenger car flow rates were calculated using headways of passenger cars not in a platoon behind a heavy vehicle. In addition to linear speed-flow models, concave models were estimated, as suggested by the theory of Erlander. Speed decrease due to increasing flow rate was smaller on Finnish highways than estimated by the new "Highway Capacity Manual" (HCM 2000). Capacity was, however, reached at lower densities so that the HCM 2000 capacity estimates appear plausible. The effects of directional distribution on average travel speed and capacity have been demonstrated and estimated.