  In vehicular ad-hoc networks (VANETs) the impact of vehicles as obstacles has
largely been neglected in the past. Recent studies have reported that the
vehicles that obstruct the line-of-sight (LOS) path may introduce 10-20 dB
additional loss, and as a result reduce the communication range. Most of the
traffic mobility models (TMMs) today do not treat other vehicles as obstacles
and thus can not model the impact of LOS obstruction in VANET simulations. In
this paper the LOS obstruction caused by other vehicles is studied in a highway
scenario. First a car-following model is used to characterize the motion of the
vehicles driving in the same direction on a two-lane highway. Vehicles are
allowed to change lanes when necessary. The position of each vehicle is updated
by using the car-following rules together with the lane-changing rules for the
forward motion. Based on the simulated traffic a simple TMM is proposed for
VANET simulations, which is capable to identify the vehicles that are in the
shadow region of other vehicles. The presented traffic mobility model together
with the shadow fading path loss model can take in to account the impact of LOS
obstruction on the total received power in the multiple-lane highway scenarios.
