  Single vehicle data obtained from magnetic loops on an expressway allowed us
to measure velocity correlations and velocity differences between non--neighbor
vehicles on the same lane, showing some strong correlations even for platoons
of 7 or 8 vehicles. The corresponding time headway distribution for
non--neighbor vehicles is also presented. We were also able to get some
informations about inter--lane structures, through crossed time headway
distributions. It should be noticed that these last results on crossed time
headways are meaningful only because the subset of data we used corresponds to
a unique stationary traffic state -- and still contains a large amount of data,
with a large fraction of short time headways. The link with passing maneuvers
is discussed.
